Early release, published at www.cmaj.ca on July 15, 2010. Subject to revision.
Review
CMAJ
CANADIAN GUIDELINES FOR IMMIGRANT HEALTH
Tuberculosis: evidence review for newly arriving
immigrants and refugees
Christina Greenaway MD MSc, Amelia Sandoe MPH, Bilkis Vissandjee PhD, Ian Kitai MB BCh,
Doug Gruner MD, Wendy Wobeser MD MSc, Kevin Pottie MD, Erin Ueffing BHSc MHSc, Dick
Menzies MD MSc, Kevin Schwartzman MD MPH; for the Canadian Collaboration for Immigrant
and Refugee Health
Abstract
Key points
Background: The foreign-born population bears a disproportionate health burden from tuberculosis, with a rate of
active tuberculosis 20 times that of the non-Aboriginal
Canadian-born population, and could therefore benefit
from tuberculosis screening programs. We reviewed evidence to determine the burden of tuberculosis in immigrant
populations, to assess the effectiveness of screening and
treatment programs for latent tuberculosis infection, and to
identify potential interventions to improve effectiveness.
•
Foreign-born people account for 65% of all those with
active tuberculosis in Canada, and subgroups have up to a
500-fold increased risk of active tuberculosis compared
with the non-Aboriginal Canadian-born population.
•
The Canadian Collaboration for Immigrant and Refugee
Health recommends screening certain groups as soon as
possible on arrival in Canada with a tuberculin skin test
and treating for latent tuberculosis infection in those
found to be positive, after ruling out active tuberculosis.
•
Although isoniazid is highly efficacious in decreasing the
development of active tuberculosis in those with latent
tuberculosis infection, monitoring for hepatotoxicity is
required for all ages; close monitoring is required for those
over 50 years of age and those with pre-existing liver disease,
alcoholism or concomitant use of hepatotoxic drugs.
Methods: We performed a systematic search for evidence of
the burden of tuberculosis in immigrant populations and the
benefits and harms, applicability, clinical considerations, and
implementation issues of screening and treatment programs
for latent tuberculosis infection in the general and immigrant populations. The quality of this evidence was assessed
and ranked using the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation).
• Adherence to screening and treatment for latent
tuberculosis infection can be increased if delivered in a
culturally sensitive manner.
Results: Chemoprophylaxis with isoniazid is highly efficacious in decreasing the development of active tuberculosis
in people with latent tuberculosis infection who adhere to
treatment. Monitoring for hepatotoxicity is required at all
ages, but close monitoring is required in those 50 years of
age and older. Adherence to screening and treatment for
latent tuberculosis infection is poor, but it can be increased
if care is delivered in a culturally sensitive manner.
Active pulmonary tuberculosis was recently diagnosed in Harjit,
a 65-year-old man who immigrated to Canada from India at age
32. Diabetes was diagnosed when he was 40 years old, and
chronic renal failure developed one year ago that required dialysis because of the diabetes. Should screening for latent tuberculosis have been done for this man, and if so when?
DOI:10.1503/cmaj.090302
Interpretation: Immigrant populations have high rates of
active tuberculosis that could be decreased by screening for
and treating latent tuberculosis infection. Several patient,
provider and infrastructure barriers, poor diagnostic tests,
and the long treatment course, however, limit effectiveness
of current programs. Novel approaches that educate and
engage patients, their communities and primary care practitioners might improve the effectiveness of these programs.
Introduction
Tuberculosis is an airborne transmissible disease that causes a
substantial burden to patients, their contacts and society.
Although tuberculosis is relatively uncommon in Canada
The cases
Ousman, a 32-year-old man; his 8-year-old daughter, Nene;
and his 65-year-old mother, Mariama, from Casamance,
Senegal, speak only Wolof and arrived in Canada six months
ago from a refugee camp. What, if any, screening for latent
tuberculosis should be done for this family?
From the Division of Infectious Diseases and Clinical Epidemiology and Community Services Unit (Greenaway, Sandoe), SMBD Jewish General Hospital, McGill
University, Montréal, Que.; the Faculty of Nursing (Vissandjee), University of
Montreal, Montréal, Que.; the Department of Paediatrics, Division of Infectious
Diseases (Kitai), Hospital for Sick Children, University of Toronto, Toronto, Ont.;
the Department of Family Medicine (Gruner), University of Ottawa, Ottawa,
Ont.; the Department of Medicine, Division of Infectious Diseases (Wobeser),
Queen’s University, Kingston, Ont.; the Institute of Population Health (Pottie,
Ueffing), University of Ottawa, Ottawa, Ont.; and the Montreal Chest Institute
(Menzies, Schwartzman), McGill University, Montréal, Que.
CMAJ 2010. DOI:10.1503/cmaj.090302
CMAJ
© 2010 Canadian Medical Association or its licensors
1
Review
Box 1: Recommendations for preventing tuberculosis from the Canadian
Collaboration for Immigrant and Refugee Health
Children
Screen children and adolescents ≤ 20 years of age from countries with a high
incidence of tuberculosis (smear-positive pulmonary tuberculosis ≥ 15/100 000
population) as soon as possible after their arrival in Canada with a tuberculin skin
test and recommend treatment for latent tuberculosis infection if results are
positive, after ruling out active tuberculosis.
programs for latent tuberculosis, to identify barriers or challenges to implementation of such programs and to highlight
possible interventions to improve these
programs. The recommendations for preventing tuberculosis from the Canadian
Collaboration for Immigrant and Refugee
Health are found in Box 1.
Adults
Screen all refugees, between the ages of 21 and 50 years, from countries with a
high incidence of tuberculosis as soon as possible after their arrival in Canada with
a tuberculin skin test. Screen all other adult immigrants if they have risk factors
that increase the risk of active tuberculosis with a tuberculin skin test and
recommend treatment for latent tuberculosis infection if results are positive, after
ruling out active tuberculosis.
Basis of recommendations
Balance of benefits and harms*
The decision about whom to screen and offer treatment for latent tuberculosis is
based on the balance between the potential benefit of treatment (decreasing the
lifetime risk of active tuberculosis, which is influenced by age, the presence of
underlying medical conditions and immigration category) versus the potential harm
of hepatotoxicity (that increases with age) and the poor effectiveness of isoniazid in
many settings because of suboptimal uptake of screening and treatment. For several
groups, screening for latent tuberculosis should be routinely performed, and those
with positive results should be offered treatment. These groups are children from
countries with a high incidence of tuberculosis (number needed to treat [NNT] 20–26;
number needed to harm [NNH] 134–268), adults with risk factors for active
tuberculosis (NNT 3–20; NNH variable) and refugees < 50 years of age (NNT 15–26;
NNH 49). Screening for latent tuberculosis and offering treatment could also be
considered for adult refugees 50–65 years of age (NNT 20–51; NNH 9–18) and other
adults without underlying medical conditions < 65 years of age if adherence to
treatment could be ensured and hepatotoxicity carefully monitored to minimize
harm. A decision to screen is a decision to offer treatment and to ensure adherence
to treatment with appropriate counselling and monitoring.
Methods
We used the 14-step approach developed
by the methods team of the Canadian
Collaboration for Immigrant and Refugee
Health.4 The Clinician Summary Table
highlights the population of interest, the
epidemiology of disease within this population, population-specific considerations
and potential key clinical actions (Appendix 1, available at www .cmaj .ca /cgi
/content/full/cmaj.090302/DC1). We then
constructed a logic model to define the
clinical preventive actions (intervention),
outcomes and key clinical questions.
Details of the review are summarized in
the tuberculosis technical document
(www.ccirh.uottawa.ca).
Search strategy for systematic
reviews, guidelines and populationspecific literature
Quality of evidence
We designed a search strategy in consulHigh
tation with a librarian to identify relevant
Values and preferences
systematic reviews and guidelines to
The guideline committee attributed more value to screening and treating latent
address the burden of tuberculosis and
tuberculosis infection to prevent active disease in patients and to prevent
the
effectiveness of screening programs
transmission of active disease and less value to the practitioner burden of
for tuberculosis (latent and active) in the
screening and counselling.
immigrant population. For this search, we
*Estimated NNT and NNH are based on the following assumptions: Seven years after arrival, the annual
risk of active tuberculosis is 0.1%; the relative risk of active tuberculosis is highest upon arrival and
reviewed five electronic databases:
decreases with time (relative risk 5.1, compared with 1.4 seven years after arrival); the patient will live to
MEDLINE (Ovid), MEDLINE Inage 80 years; the efficacy of isoniazid is 90%; and adherence is 70%.
Process, EMBASE, CINAHL and the
Cochrane Database of Systematic
(1621 cases reported in 2006), it is costly ($58 million in
Reviews from 1950 to Dec. 17, 2008. We conducted a similar
direct costs in Canada in 2004), treatment is lengthy, many
search for the general population, with the same five databases
and the same objectives but restricted the search dates to Jan.
patients require admission to hospital, and the mortality rate
1, 1996 to Dec. 17, 2008. We performed a separate search for
in patients with tuberculosis is still high (11%).1,2
tuberculosis among immigrants to address population-specific
The foreign-born population bears a disproportionate burden
concerns including baseline risk or prevalence compared with
of tuberculosis in Canada; 65% of all cases of active tuberculothe Canadian-born population; risk of clinically important outsis occur in foreign-born patients although they make up only
comes; genetic and cultural factors (e.g., preferences, values,
20% of the population.3 This is because most recent immigrants
knowledge); and compliance variation using the same five
and refugees originate from countries with a high incidence of
databases (1950 to Dec. 17, 2008). An updating search, focustuberculosis, and up to half harbour latent tuberculosis infection
ing on randomized controlled trials and systematic reviews
and are at risk of active tuberculosis.2 Successful control of
during the period Jan. 1, 2007 to Jan. 1, 2010, was conducted
tuberculosis in Canada will depend on decreasing rates of
to identify any recent publications that would change the posituberculosis in the foreign-born population. We conducted a
tion of the recommendation. We performed a Web-based
review to quantify the burden of tuberculosis in the migrant
search until September 2007 to identify guidelines on tubercupopulation, to identify those at highest risk of active tuberculolosis screening and treatment in the following websites: the
sis, to describe the effectiveness of screening and treatment
2
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Review
Box 2: Grading of Recommendations Assessment,
Development and Evaluation Working Group grades of
evidence (www.gradeworkinggroup.org)
•
High quality: Further research is very unlikely to change
our confidence in the estimate of effect.
•
Moderate quality: Further research is likely to have an
important impact on our confidence in the estimate of
effect and may change the estimate.
•
Low quality: Further research is very likely to have an
important impact on our confidence in the estimate of
effect and is likely to change the estimate.
•
Very low quality: We are very uncertain about the estimate.
Identification
CMA Infobase; the National Guideline Clearing House; the
Canadian Task Force on Preventive Health Care; the Public
Health Agency of Canada; the Canadian Lung Association;
the US Preventive Task Force; Centers for Disease Control
and Prevention; Infectious Disease Society of America; American Thoracic Society; National Institute for Health and Clinical Excellence; and the World Health Organization. We
appraised eligible systematic reviews using the critical
appraisal tool of the National Institute for Health and Clinical
Evidence to assess systematic
approach, transparency, quality of
methods and relevance. We assessed
relevant guidelines using the
Appraisal of Guidelines for Research
and Evaluation (AGREE) Instrument
(www.agreecollaboration.org).
and 9 met the eligibility criteria. They included two guidelines
from the United States that addressed screening for latent
tuberculosis infection in immigrants, 5,6 three articles that
addressed tuberculosis screening issues in foreign-born
patients,7–9 one review of postlanding surveillance in Canada,10
and three narrative reviews of screening immigrants and
refugees that recommended screening for latent tuberculosis
infection in immigrants and refugees, but none used a systematic review method.11–13
In the search for systematic reviews and guidelines for
research involving the general population and tuberculosis,
3968 articles were identified, and 18 met the eligibility criteria.
These reviews addressed diagnostic tests for latent tuberculosis
infection,14,15 the effect of bacille Calmette-Guérin (BCG) on
the tuberculin skin test,16–18 screening,7,19,20 factors that increase
the risk of active tuberculosis,21–23 efficacy of treatment for
latent tuberculosis infection24 and adherence to treatment,25 and
included four US guidelines on controlling tuberculosis and
treating latent tuberculosis infection.6,26–28 A flow chart of these
combined searches is outlined in Figure 1. We identified the
Canadian tuberculosis standards in the Web-based search.2 In
the immigrant and tuberculosis search, 3073 primary articles
were identified, of which 609 were relevant and addressed the
Records
excluded
n = 3836
Full-text articles assessed for
eligibility
n = 112
Full-text articles
excluded with
reasons*
n = 67
Eligible systematic reviews or
guidelines
n = 45
Eligible articles
excluded†
n = 27
Guidelines or systematic reviews
focusing on tuberculosis included
for summary of findings tables and
discussion of effectiveness
n = 18
Screening
Records screened (titles and
abstracts)
n = 3948
Eligibility
Duplicates removed
n = 2958
Included
Synthesis of evidence and values
Evidence from systematic reviews,
cohort studies and clinical trials using
the summary of findings table from
Grading of Recommendations Assessment, Development and Evaluation
(GRADE) (Box 2), which assesses
both relative and absolute effects of
interventions (relative risk and
absolute event rate), was synthesized.
We appraised quality of data for each
outcome using the GRADE quality
assessment tool, which assesses study
limitations, directness, precision, consistency and publication bias across
all studies. In the search and synthesis
of data on concerns specific to immigrants, clinically relevant considerations and implementation issues, as
well as gaps in the research and evidence base, were identified.
Records identified through
database search
n = 6906
Results
In the search for systematic reviews
and guidelines for immigrants, 176
records were identified and screened,
Figure 1: Literature search for systematic reviews and guidelines on tuberculosis.
*Excluded because of lack of relevance. †Excluded because of lack of relevance, poor quality or outdated findings.
CMAJ
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Review
following areas: epidemiology, diagnosis, screening, adherence
and treatment for latent tuberculosis infection in immigrants.
What is the burden of tuberculosis in
immigrant populations?
Tuberculosis is an important global health burden, with more
than one billion people infected with latent tuberculosis result-
ing in 9.2 million new active cases and 1.5 million deaths per
year (> 95% occur in low- to middle-income countries).29
Canada is a low-incidence country, with an overall rate of
active tuberculosis of 5 cases/100 000 population.3,30,31 Most of
these cases (> 65%) occur in foreign-born patients, who have
an incidence of tuberculosis 20 times that in the non-Aboriginal Canadian-born population (16 v. 0.8 cases/100 000 population) but with rates as high as 500 times those in certain subgroups of immigrants (Table 1).8,32,33 In the past 40 years, most
Table 1: Incidence of tuberculosis/100 000 population for immigrants and refugees after arrival in high-income countries
Time since migration; incidence per 100 000 population
Country of origin
≤ 1 yr
Overall rate
> 1–5 yr
≥ 5 yr
37
17
All world regions
All foreign-born*†8,32,33
35
37
Refugees received by US‡
128
504
Latin America and Caribbean†
All foreign-born8,32,33
17
76
26
10
Mexico8
19
75
22
11
Haiti8
55
428
98
28
Guatemala
32
173
58
12
Peru8
47
233
90
23
All foreign-born8,32,33
17
65
19
13
33
80
240
50
27
8
Eastern Europe and Central Asia
Former Yugoslavia
Refugees received by US37
162
Middle East and North Africa
All foreign-born8,32
8
47
15
5
48
Sub-Saharan Africa
All foreign-born8,32,33†
133
1120
120
8
Ethiopia
159
1515
189
59
Somalia33
710
1540
560
433
22
Refugees received by US37
1107
South Asia
All foreign-born8
36
179
52
India8
40
150
51
21
240
530
255
157
58
33
Pakistan33
East Asia and Pacific
All foreign-born†8,32,33
53
284
8
52
543
66
30
Vietnam†8,33
87
602
112
51
China8,32
28
129
27
19
51
158
67
32
Philippines
8
South Korea
Refugees received by US37
Low-incidence countries8,32
877
1.7
3.0
2.0
8,32,33
*Total number of cases of tuberculosis in foreign-born immigrants and refugees = 11 359.
8,32,33
8,33
†Overall rate is a weighted average of all three studies
and stratified rates are a weighted average of two studies.
‡Total number of cases of tuberculosis in refugee population immigrated to the USA = 91 and total refugee population = 18 060.37
4
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1.6
Review
new immigrants have originated from high-incidence countries (i.e., > 15 cases of smear-positive pulmonary tuberculosis/100 000 population), 30%–50% of whom are infected with
latent tuberculosis, resulting in a reservoir of approximately
1.5 million people in Canada with latent tuberculosis infection
who are at risk of active tuberculosis.2
The prevalence of latent tuberculosis infection and the
presence of factors associated with increased risk of active
tuberculosis determine the people in whom active tuberculosis will develop. People with positive results of tuberculin
skin tests who live in a low-incidence country and have no
risk factors have an estimated annual probability of active
tuberculosis developing of only 0.1% per year. This means
that active disease will develop in only 5%–10% of those
with latent tuberculosis infection.21 Recent transmission of
tuberculosis confers an increased risk of active tuberculosis.
This is extrapolated from studies in which 1%–2% of contacts
have active tuberculosis immediately after diagnosis of the
index cases. The highest risk of active tuberculosis occurs in
the first year after exposure and decreases to the baseline risk
(0.1% per year) 5 to 10 years after exposure.2,23
The strongest predictors for active tuberculosis in immigrant populations are global region of origin, immigration category, the presence of underlying medical comorbidity and
the time since arrival.
two-fold greater one to four years after arrival (Table 1).8,32,33
This increase is most likely caused by the effect of recent
exposure to tuberculosis before arrival.39 A practical Webbased tool can be used to help calculate the lifetime risk of
active tuberculosis based on these factors (www.tstin3d
.com/index.html)40 (Tables 1 and 2).41–80
Do screening and treatment for latent
tuberculosis decrease morbidity from active
tuberculosis?
Screening tests
The tuberculin skin test and interferon gamma release assays
(IGRAs) are available for diagnosing latent tuberculosis infection. The sensitivity of these tests is estimated to be 70%–
90%, and the specificity for all tests is > 95% except for the
tuberculin skin test in patients vaccinated with BCG (60%)
Region of origin
Rates of tuberculosis are highest in immigrant populations
that originate from world regions with the highest rates of
tuberculosis, such as sub-Saharan Africa and Asia. Immigrants from these regions (rates of smear-positive pulmonary
tuberculosis of 200–300/100 000 population) are more likely
to be heavily exposed to tuberculosis, to have positive results
of tuberculin skin tests and to have recently been exposed to
tuberculosis.29
Table 2: Relative risk of developing active tuberculosis in the
presence of underlying medical conditions
Variable
Relative risk (RR)
High risk (RR > 6*)
AIDS
110–17041,42
HIV infection
10–11043,44
Transplantation (related to
immunosuppressant therapy)
20–7445-48
Leukemia, lymphoma
1.0–3549,50
Silicosis
1.5–3351,52
Chronic renal failure requiring
hemodialysis
1.6–2553-56
Carcinoma of head and neck
Recent tuberculosis infection (≤ 2 yr)
1657
1558,59
Immigration category
The risk of active tuberculosis in refugee populations is about
double that in immigrant populations (Table 1).34–37 This is
likely due to both a higher prevalence of latent tuberculosis
infection and having lived in crowded conditions that increase
the likelihood of recent exposure to tuberculosis.38
Abnormal results of chest radiography:
fibronodular disease
6–1960-62
Tumour necrosis factor alpha inhibitors
1.7–963-66
Presence of underlying comorbidity
Underlying medical illnesses, especially any conditions that
decrease local or systemic immunity, increase the rate of
active tuberculosis to varying degrees, with HIV being the
strongest risk factor. The issue of HIV screening in new
immigrants and refugees is discussed in the HIV evidence
review in this series.
Young when infected (0–4 yr)
Time since arrival
Rates of tuberculosis in immigrant and refugee populations,
from all world regions, are highest within the first five years
after arrival in a low-incidence region but decrease dramatically after the first year of arrival. Rates of active tuberculosis
in the immigrant population, as compared with five years
after arrival, are 5 to 10 times greater in the first year and
Refugees
CMAJ
Intermediate risk (RR = 3–6*)
Treatment with glucocorticoids
Diabetes mellitus (all types)
4.967
2.0–4.168-71
2.2-572
Low/intermediate risk (RR = 1.3–3*)
Underweight (< 90% ideal body weight;
for most people, a body mass index
≤ 20)
Cigarette smoker (1 pack per day)
Abnormal results of chest radiography:
granuloma
1.6–373-75
2–376,77
261,78
237,38,62,79
Low risk (RR = 1†)
Infected person, no known risk factor,
normal results of chest radiography
(“low-risk reactor”)
180
*Mean relative risk for each variable falls in this range.
†Incidence of active tuberculosis developing, 0.1%/yr.
5
Review
owing to cross-reactivity.15 With tuberculin skin tests, the likelihood of a false-positive result caused by BCG decreases with
time since vaccination, but it also depends on the age when the
person was vaccinated. In the first 10 years after vaccination,
up to 42% of patients vaccinated after age two will have positive results of tuberculin skin tests (even fewer of patients vaccinated as neonates), but data on the rate of decline conflict.17,81–84 In those receiving a tuberculin skin test less than 10
years after vaccination as a neonate, only 1%–2% of results
will be positive, compared with 21% in those vaccinated after
age two. Interpreting results of a tuberculin skin test is therefore particularly difficult in children less than 10 years of age.
All HIV-positive patients should be screened for latent tuberculosis infection with a tuberculin skin test.2
Because there is no criterion standard for the diagnosis of
latent tuberculosis infection, assessing and comparing the perfor-
mance of these tests is challenging, especially when there are discrepancies. The major advantage of the tuberculin skin test over
IGRAs is that the risk of active disease for different sizes of
induration in tuberculin skin testing is well described, whereas
very few prospective data exist for IGRAs. The most recent
Canadian guidelines recommend using the tuberculin skin test as
the primary screening tool for both adults and children and using
IGRAs sequentially after tuberculin skin test in people with a
high likelihood of a false-positive result from tuberculin skin test
(i.e., low risk of tuberculosis infection).85 This recommendation is
supported by a recent cost-effectiveness analysis.86 The major
limitation of these tests is their inability to distinguish the 10% of
people with latent tuberculosis infection in whom active tuberculosis will develop from the 90% in whom it will not.
Once a tuberculin skin test has been performed and the results
found to be positive, all patients should undergo chest radiogra-
Table 3: Summary of findings table on isoniazid to prevent active tuberculosis
Patient or population: Varied: Smieja et al24 = populations at risk for developing active tuberculosis, with HIV-positive patients
excluded; Bucher et al87 = HIV-positive patients
Setting: Varied: Smieja et al24 = US psychiatric institutions, veterans’ hospitals in US, Eastern Europe, Alaska, Hong Kong, India, etc.;
Bucher et al87 = Mexico, Haiti, US, Zambia, Uganda and Kenya
Intervention: Isoniazid treatment to prevent active tuberculosis
Comparison: No treatment
Source: Smieja MJ, Marchetti CA, Cook DJ, et al. Isoniazid for preventing tuberculosis in non-HIV infected persons [review].
Cochrane Database Syst Rev 1999(1):CD001363.24
Bucher HC, Griffith LE, Guyatt GH, et al. Isoniazid prophylaxis for tuberculosis in HIV infection: a meta-analysis of randomized
controlled trials. AIDS 1999;13(4):501–7.87
Absolute effect
Outcomes, risk category
Risk for
control group
Difference
with isoniazid
(95% CI)
Relative effect
(95% CI)
No. of
participants
(studies)
GRADE quality
of evidence
Comments
(95% CI)
Active tuberculosis*†
Intermediate risk*
17/1000
10 fewer per
1000
(12 fewer to 8
fewer per
1000)
RR 0.40
(0.31–0.52)
73 375 (11)
Moderate‡§
NNT 99
(86–123)
Highly compliant
(take > 80% of
doses)*
10/10 000
7 fewer per
10 000
(8 fewer to 5
fewer per
10 000)
RR 0.20
(0.13–0.31)
15 696 (1)
High
NNT 85
(78–98)
High risk†
53/1000
32 fewer per
1000
(40 fewer to
19 fewer per
1000)
RR 0.40
(0.24–0.65)
1 875 (5)
Moderate¶
NNT 32
(25–54)
1/1000
5 more per
1000
(2 more to 11
more per
1000)
RR 5.54
(2.56–12)
20 874 (1)
Moderate
NNH 220
(91–642)
Hepatitis
(follow-up: 5 yr)††
Note: CI = confidence interval, GRADE = Grading of Recommendations Assessment, Development and Evaluation, NNT = number needed to harm, NNT = number
needed to treat, RR = risk ratio.
24
*Numbers taken from Smieja et al.
87
†In 1999 systematic review of isoniazid for tuberculosis in HIV-positive patients, this is the risk in HIV-positive, tuberculin skin test–positive patients.
‡Test for heterogeneity p = 0.02.
§Only one study examined 6 months of isoniazid v. 12 months; risk of hepatitis and active tuberculosis not significantly different between groups.
¶Downgraded for directness, as data from developing countries.
88
24
**Thompson as reported in Smieja et al.
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Review
phy to rule out active tuberculosis and be questioned for symptoms of active tuberculosis (chronic cough, weight loss, fever,
night sweats). If there is any suspicion of active tuberculosis,
three samples of sputa or specimens from other sites (e.g., lymph
node, cerebrospinal fluid) should be gathered for smear and culture before treatment for latent tuberculosis infection is started.
Relative benefits and harms of treatment
The efficacy of isoniazid compared with placebo in decreasing
the likelihood of active tuberculosis developing in people with
latent tuberculosis infection has been established in a Cochrane
review (relative risk 0.40, 95% confidence interval 0.31–0.52)
of 11 randomized controlled trials (Tables 3 and 4).24,87 The overall efficacy of isoniazid is 62% after 12 months of treatment but
increases to 93% in those who adhere to treatment (i.e., take >
80% of their doses).88 Although a direct comparison of the efficacy of treatment for 9 versus 12 months has not been done, in a
recent reanalysis, the maximal benefit of isoniazid was achieved
at 9 months (Tables 5 and 6).89 A study on the effect of isoniazid
resistance on efficacy of isoniazid chemoprophylaxis found that,
at a mean prevalence of 7%–10% isoniazid resistance (the level
in the immigrant population), isoniazid was the drug of choice
and that only at very high rates (> 15%–20%) of isoniazid resistance were other regimens preferred.90,91
Hepatoxicity is a limitation of isoniazid therapy. It most
commonly manifests as a transient asymptomatic increase in
liver function (10%–20%), rarely causes clinical hepatitis
(0.5%) — which resolves when treatment with isoniazid is
stopped92,94,95 — and very rarely causes fulminant hepatitis and
liver failure (< 0.01%) leading to death or liver transplantation.28,96–98 Initial higher overall rates of hepatotoxicity (1%)
were reported among adults in the 1970s but were likely confounded by unrecognized underlying cirrhosis.99,100 Hepatoxicity among patients taking isoniazid is increased in those
with pre-existing liver disease, alcoholism, concomitant use
of hepatotoxic drugs and older age (Table 7). Although clinical and fulminant hepatitis are rare, they can occur at any age;
this possibility underscores the importance of monthly monitoring for all patients and of teaching them to recognize
symptoms of hepatitis (nausea, vomiting, abdominal pain,
jaundice) and to stop medication as soon as worrisome symptoms occur.28,96 Adequate time must be taken, through interpreters if necessary, to ensure that all patients are appropriately informed and understand the risks and benefits of
isoniazid, and they must be given a clear description of what
to do if symptoms arise.
Clinical considerations
How are immigrants screened for tuberculosis
before and after arrival to Canada?
All people applying for permanent residency, people claiming
refugee status, and students and workers staying for more than
six months are screened for active tuberculosis infection with
chest radiography, followed by sputum culture if radiographic
results are abnormal. Those found to have active tuberculosis
must prove that they have been adequately treated and have negative results of culture before entry to Canada. Patients with previously treated tuberculosis or inactive tuberculosis (defined as
those with latent tuberculosis infection and scarring visible on
chest radiograph) are required to begin monitoring within 30
days after arrival in Canada in the Post-Landing Surveillance
Program. 2,10,20 There are no routine postlanding screening programs for latent tuberculosis infection for immigrants in Canada,
but several programs exist (managed by different organizations)
— for example, school-based screening, contact investigations,
immigrant and refugee clinics, services for migrant workers and
targeted screening of high-risk and undocumented migrants.106–123
Table 4: Summary of findings for using isoniazid among all age groups with latent tuberculosis infection
Patient or population: Patients with latent tuberculosis
Setting: Tuberculosis clinics in Memphis, Tennessee
Intervention: Isoniazid treatment to prevent active tuberculosis
Comparison: Younger people compared with older people
Source: Fountain FF, Tolley E, Chrsman CR, et al. Isoniazid hepatotoxicity associated with treatment of latent tuberculosis
infection: a 7-year evaluation from a public health tuberculosis clinic. Chest 2005;128:116-23.92
Absolute effect
Risk for
control
group
Outcomes
Toxicity
elevation of
transaminases
by more than
five times
upper limit of
normal
Difference with older age
(95% CI)
Age 25–34
Age 35–49
Age 50+
4/1000
4 more per
1000
(2 fewer to
21 more
per 1000)
15 more per
1000
(2 more to
58 more per
1000)
Relative effect
(95% CI)
Age
35–49
Age
50+
RR
1.94
(0.59–
6.34)
RR 4.74
(1.40–
15.49)
No. of
participants
(studies)
GRADE
quality of
evidence
2182 (1)
Very low*
Comments
(95% CI)
Age
35–49
Age
50+
NNH 266
(NS)
NNH 67
(18–625)
Note: CI = confidence interval, GRADE = Grading of Recommendations Assessment, Development and Evaluation, NNH = number needed to harm, NNT = number
needed to treat, NS = not statistically significant, RR = risk ratio.
*Fewer than 300 events.
CMAJ
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tuberculosis infection (30%–50% of all immigrants from
countries in which tuberculosis is endemic) currently living in
Canada or arriving in Canada each year. This pool includes
not only one million people arriving annually from countries
in which tuberculosis is endemic (visitors, students, temporary workers, etc.) but also the approximately four million
people originating from countries in which tuberculosis is
endemic who already live in Canada.127–129 Finally, exposure to
tuberculosis caused by ongoing mobility of this population
through travel to their countries of origin to visit family and
friends could be substantial.130,131
Effectiveness of screening programs
The preimmigration radiographic screening and the Post-Landing Surveillance Program have relatively little effect on controlling tuberculosis in Canada. Of all immigrants screened for
tuberculosis before immigration, less than 1% are found to
have active tuberculosis, and 3%–5% (8000–13 000 people/yr)
are found to have inactive tuberculosis.2,9 Despite forming a
high-risk group for active tuberculosis, they account for only a
small proportion of all cases of tuberculosis in the foreign-born
population (8% in a study in Alberta), which could in part be
due to program limitations.107,124–126
All the domestic screening programs (school-based, targeted immigrant or refugee, or contact tracing) for latent
tuberculosis infection perform suboptimally; only about 47%
(range 11%–72%) of people with positive results of tuberculin skin tests actually complete treatment.106,123 This suboptimal performance is caused by losses and dropouts at the
many different steps in the process, including failure to present for or complete screening, failure to report for medical
evaluation if screening test is positive, physicians’ failure to
prescribe chemoprophylaxis for those eligible, patients’
refusal to start treatment and failure to complete a course of
isoniazid.7 Suboptimal screening is compounded by the fact
that there is a large pool of foreign-born patients with latent
What should be considered when screening and
treating?
Children
Children less than 11 years of age do not undergo prearrival
radiographic screening; for this and several other reasons, they
could benefit greatly from screening for latent tuberculosis
infection. There are many years of life in which active tuberculosis could develop in children, and children have a relatively
low potential for hepatotoxicity (Table 7).99 If active tuberculosis develops, it is often difficult to diagnose because it is more
often paucibacillary or extrapulmonary, and young children
Table 5: Estimated numbers needed to treat for latent tuberculosis infection to prevent one case of active tuberculosis by age, time
since arrival and adherence
Age (yr)
10
20
35
50
65
Number needed to treat
Years lived in
Canada
Cumulative
lifetime risk of
active
tuberculosis
(%)*†
100%
70%
50%
30%
0
8.1
14
20
28
46
2
7.5
15
22
30
50
5
7.1
16
23
31
52
0
7.1
16
23
32
52
2
6.5
18
25
35
57
5
6.1
18
26
36
60
0
5.6
20
29
40
66
2
5.0
23
32
45
75
5
4.6
24
34
48
80
0
4.1
28
39
55
91
2
3.5
32
46
64
107
5
3.1
36
51
71
118
0
2.6
44
62
87
144
2
2.0
57
81
113
188
5
1.6
68
97
136
226
Course of isoniazid completed (%)‡
*Assume 0.1% annual risk of infection with a relative risk of active tuberculosis developing for each year since arrival of < 1 yr 5.08, 1.1–2 yr 2.96, 2.1–3 yr 2.35,
21,32,92
3.1–4 yr 2.06, 4.1–5 yr 1.87, 5.1–6 yr 1.89, 6.1–7 yr 1.36 all v. > 7 yr.
†Assume subjects live to age 80 yr.
24,88
‡For 100% completion, assume 90% efficacy of isoniazid.
8
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Table 6: Estimated numbers needed to treat for latent tuberculosis infection to prevent one case of active tuberculosis in those
with high and intermediate risk for development of active tuberculosis by age, time of arrival and adherence
Age (yr), level of risk
Years lived in
Canada
Lifetime risk
of active
tuberculosis (%)*
Number needed to treat
Lifetime risk of
active tuberculosis
with risk factor
(%)†‡
100%
70%
50%
30%
Course of isoniazid completed§
35 yr
High
RR = 10**
Intermediate
RR = 5**
Low/intermediate
RR = 2**
0
5.6
56
2
3
4
7
2
5.0
50
3
4
5
8
5
4.6
46
3
4
5
8
0
5.6
28
4
6
8
14
2
5.0
25
5
7
9
15
5
4.6
23
5
7
10
16
0
5.6
11
10
15
20
33
2
5.0
10
12
16
23
38
5
4.6
9
12
17
24
40
0
4.1
41
3
4
6
10
2
3.5
35
4
5
7
11
5
3.1
31
4
6
8
12
0
4.1
20
6
8
11
19
2
3.5
17
7
10
13
22
5
3.1
16
8
11
15
24
0
4.1
8
14
20
28
46
2
3.5
7
16
23
32
54
5
3.1
6
18
26
36
59
0
2.6
26
5
7
9
15
2
2.0
20
6
9
12
19
5
1.6
16
7
10
14
23
0
2.6
13
9
13
18
29
2
2.0
10
12
16
23
38
5
1.6
8
14
20
28
46
0
2.6
5
22
31
44
72
2
2.0
4
29
41
57
94
5
1.6
3
34
49
68
113
50 yr
High
RR = 10**
Intermediate
RR = 5**
Low/intermediate
RR = 2**
65 yr
High
RR = 10**
Intermediate
RR = 5**
Low/intermediate
RR = 2**
Note: RR = relative risk.
*Assume 0.1% annual risk of infection with a RR for active tuberculosis developing for each year since arrival of: < 1 yr 5.08, 1.1–2 yr 2.96, 2.1–3 yr 2.35, 3.1–4 yr
21,32,92
2.06, 4.1–5 yr 1.87, 5.1–6 yr 1.89, 6.1–7 yr 1.36 all v. > 7 yr.
†Multiply lifetime risk by relative risk.
‡Assume subjects live to age 80 yr.
§Proportion of patients prescribed isoniazid who completed a course of treatment.
24,88
¶For 100% completion, assume 90% efficacy of isoniazid.
**Midpoint of range. See Table 2 for range of RR for each category classified as high, intermediate, low/intermediate risk and associated conditions.
CMAJ
9
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Increased adherence to tuberculin skin test screening has
been seen with patient reminders (e.g., letters, phone calls),
education of patients and physicians, and novel strategies,
such as drive-by tuberculin skin test readings for taxi drivers.137,139,143 One study educating primary care providers on
how and whom to screen for tuberculosis not only increased
screening and identification of people with latent tuberculosis, but also increased identification of those with active
tuberculosis. In this randomized clinical trial, screening was
0.4% and 57% in the nonintervention and intervention
groups respectively, and identification of both those with
latent tuberculosis infection (9% to 19%) and those with
active tuberculosis (34% v. 47%) increased.137 Strategies that
have increased adherence to treatment for latent tuberculosis
infection in immigrant and refugee populations include
patient reminders (calendar stickers for self-monitoring,
phone calls, letters and directly observed therapy), adherence
coaches who speak the same language as the patient, ongoing education of patients and providers, and cultural case
management. 25,144–146 Goldberg and colleagues found that
when case managers were matched to the ethnic and linguistic background of patients and provided treatment for latent
tuberculosis and monitoring during monthly home visits,
adherence with treatment was substantially improved (82%
v. 37%), as compared with standard clinic-based management before the intervention.146
Table 7: Estimated number needed to harm with increasing
risk of isoniazid hepatoxicity
Prevalence of
hepatoxicity (%)
Number needed
to harm
95% confidence
interval
0.10
268
69–2513
0.20
134
35–1256
0.25
107
28–1005
0.5
54
14–503
0.75
36
9–335
1.0
27
7–251
1.25
21
6–201
1.50
18
5–168
1.75
15
4–144
2.0
13
3–126
2.25
12
3–112
2.5
11
3–101
2.75
10
3–91
3.0
9
2–84
Risk of hepatoxicity increases with age:
97,98,101–105
< 20 yr 0.1%–0.2%
92,94,95
20–35 yr 0.3%
92,94,95
35–49 yr 0.5%
92,94,95
> 50 yr 1%–3%
(especially those younger than five years of age) are more
likely susceptible to severe or rapidly progressive disease.132,133
Refugees
Refugee populations have consistently had about a two-fold
increased risk of active tuberculosis compared with the immigrant population, at least within the first year after arrival
(Table 1).34–37 A higher prevalence of latent tuberculosis infection in the refugee population and having lived in crowded
conditions that increase the likelihood of recent exposure to
tuberculosis are contributing factors.38
What are potential implementation issues?
Barriers to uptake of screening and completion of treatment for
latent tuberculosis infection include a combination of patient,
provider and institutional factors. Patient barriers include the
stigma of tuberculosis and its association with HIV, linguistic
barriers and difficulties coming to appointments because of
inconvenient clinic locations or limited clinic hours.121,134–136
Provider barriers to offering screening to migrants are related to
inadequate knowledge of which migrants should be screened or
how they should be followed up.137–139 Low adherence to treatment for latent tuberculosis infection is associated with barriers
similar to those with screening latent tuberculosis. They include
linguistic barriers, cultural taboos and stigmatization, low education level, perceived low risk of progressing from latent
tuberculosis infection to active disease, belief that positive
results from tuberculin skin tests are due to BCG, not wanting
to have venipunctures, and economic factors (costs of travel,
lack of insurance, delays in obtaining insurance, missed days at
work).134,136,140–142
10
Other recommendations
The Canadian Tuberculosis Committee, the Canadian Thoracic Society and the Canadian Paediatric Society recommend
screening with a tuberculin skin test the following people
from countries with high incidence of tuberculosis: children
younger than 15 years living in Canada for less than two
years, and people 15 years of age or older with factors that
increase the risk of active tuberculosis or within two years
after arrival if they have a known contact with tuberculosis
(Table 2).2,147 The US Centers for Disease Control and Prevention, the Infectious Disease Society of America and the
American Thoracic Society recommend screening for latent
tuberculosis infection with a tuberculin skin test or an IGRA
for all immigrants and refugees who have arrived in the US
within the previous five years, regardless of age, but with priority screening for refugees flagged for postlanding surveillance and children less than 15 years of age.5,27,148
The cases revisited
Ousman and his daughter Nene should be screened for latent
tuberculosis infection. Patients with positive results of tuberculin skin tests should be offered treatment if their risk of
active tuberculosis outweighs the low risk of hepatotoxicity.
Mariama should not be offered screening or treatment
because, at her age, the risk of hepatotoxicity outweighs the
benefit of treatment with isoniazid. Because the family speaks
only Wolof, a translator must be used to ensure that family
members understand the risks and benefits of isoniazid and
know to stop treatment if symptoms of hepatitis arise.
CMAJ
Review
Harjit likely had latent tuberculosis infection upon arrival
to Canada and at that time had an approximately 6% lifetime
risk of active tuberculosis. When diabetes developed, the risk
increased 2- to 4-fold, and chronic renal failure with dialysis
increased the risk 15-fold. Educating patients and practitioners to recognize subgroups that would benefit from targeted
screening and treatment for latent tuberculosis infection will
be essential to avoid missed opportunities for prevention.
5.
6.
7.
8.
9.
Conclusions and research needs
The magnitude of human migration from regions with high
to low incidence of tuberculosis has reached an unprecedented level. Control of tuberculosis in low-incidence settings
will require novel strategies to ensure increased uptake of
screening and completion of treatment for latent tuberculosis
in the foreign-born population. These strategies will need to
consider the challenges of accessing all foreign-born groups
at risk of latent tuberculosis infection. Investment in tuberculosis education programs for patients and providers and in
infrastructure is needed, so that screening and treatment programs for latent tuberculosis can be offered in a culturally
sensitive manner with good access to translators. Consideration should be given to developing tuberculosis prevention
programs in the context of comprehensive and integrated preventive health care in primary care, where a long-term trusting relationship can be established. Key future needs include
new diagnostic tests to identify the few patients with latent
tuberculosis infection in whom active tuberculosis will
develop, and to develop well-tolerated, short-course treatment
regimens for latent tuberculosis. Ultimately, the long-term
solution will be to invest in global tuberculosis control to
decrease the burden of tuberculosis in migrants to Canada.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
This article has been peer reviewed.
Competing interests: None declared.
Contributors: All authors contributed to conception and refinement of the
study design and to analysis and interpretation of the data. Christina Greenaway drafted the initial manuscript, and all other authors provided critical revisions. All authors approved the final manuscript submitted for publication.
24.
Acknowledgements: The authors thank Peter Tugwell, John Feightner and
Vivian Welch for their invaluable methodologic support throughout this project.
26.
Funding: Christina Greenaway and Dick Menzies receive salary support from
the Fonds de la Recherche en Santé du Québec through the Chercheur Boursier
Clinicien and Chercheur National programs, respectively. The Canadian Collaboration for Immigrant and Refugee Health Steering Committee acknowledges the funding support of the Chronic Disease Branch of the Public Health
Agency of Canada and Canadian Institutes of Health Research (Institute of
Health Services and Policy Research), the Champlain Local Health Integrated
Network and the Calgary Refugee Program. The views expressed in this report
are the views of the authors and do not necessarily reflect those of the funders.
25.
27.
28.
29.
30.
31.
32.
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Correspondence to: Dr. Christina Greenaway, SMBD Jewish
General Hospital, Division of Infectious Diseases, Rm. G-143,
3755 Cote St. Catherine Rd., Montréal QC H3T 1E2;
ca.greenaway@mcgill.ca
CMAJ
Clinical preventive guidelines for newly arrived immigrants
and refugees to Canada
This article is part of a series of guidelines for primary care
practitioners who work with immigrants and refugees. The
series was developed by the Canadian Collaboration for
Immigrant and Refugee Health.
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