How to reduce EDTA contamination in laboratory specimens: a Tunisian experience

Clin Chem Lab Med 2015; 53(1): e9–e12 Letter to the Editor Kahena Bouzid*, Ahlem Bartkiz, Aymen Bouzainne, Samia Cherif, Saddem Ramdhani, Aida Zairi, Mehdi Mrad, Afef Bahlous and Jaouida Abdelmoula How to reduce EDTA contamination in laboratory specimens: a Tunisian experience Keywords: awareness campaign; EDTA contamination; hypocalcemia; hypomagnesemia; spurious hyperkalemia; Tunisia. DOI 10.1515/cclm-2014-0686 Received July 3, 2014; accepted July 6, 2014; previously published online August 12, 2014 To the Editor, The laboratory testing process is traditionally divided into three phases: pre-analytical, analytical, and post-analytical. The ISO 15189:2012 standard for laboratory accreditation defines the pre-analytical phase as “steps starting in chronological order, from the clinician’s request and including the examination requisition, preparation of the patient, collection of the primary sample, transportation to and within the laboratory and ending when the analytical examination procedure begins” [1]. The errors made in the period prior to the sample analysis can potentially lead to a serious patient misdiagnosis and compromise patient’s treatment. Despite the large differences in actual error frequencies, all recently available studies demonstrate that the majority of all errors in the total testing process were of pre-analytical origin (32%–75%), with fewer mistakes during the analytical step (4%–32%) [2, 3]. *Corresponding author: Kahena Bouzid, Laboratory of Clinical Biochemistry, Charles Nicolle Hospital, Faculty of Medicine, University El Manar, Boulevard 9 Avril 1938, 1006 Tunis, Tunisia; and Laboratory of Engineering of Proteins and Bioactive Molecules (LR11EES24:LIP-MB), Tunis, Tunisia, Phone: +21698221333, Fax: +21671578196, E-mail: kahh2005@yahoo.fr Ahlem Bartkiz, Mehdi Mrad, Afef Bahlous and Jaouida Abdelmoula: Laboratory of Clinical Biochemistry, Charles Nicolle Hospital, Faculty of Medicine, University El Manar, Tunis, Tunisia Aymen Bouzainne, Samia Cherif, Saddem Ramdhani and Aida Zairi: Institut Supérieur des Sciences Infirmières de Tunis, Tunis, Tunisia Paramedical staff collects blood by syringe and distributes it in many tubes; every tube has a different anticoagulant such potassium ethylenediaminetetraacetic acid (EDTA), lithium heparin. After removing the needle, the tip of the syringe may transfer a droplet of EDTA to lithium heparin tube used for potassium analysis. This could lead to gross and obvious errors, resulting in spurious hyperkalemia, hypocalcemia, and hypomagnesemia [4], explained by the fact that EDTA sequesters divalent and trivalent metal ions. Therefore, EDTA contamination could be identified by the factitious hypocalcemia and hypomagnesemia [4, 5]. To ensure the accuracy of the patients’ test results, we decided to focus first on the pre-analytical phase, specifically potassium EDTA contamination and the draw order of blood samples. Our work strategy was as follows: first, we checked the prevalence of EDTA contamination as a cause of spurious hyperkalemia, hypocalcemia, and hypomagnesemia in different hospital services. Second, we made a knowledge assessment of the paramedical staff. Then, we gave the medical and paramedical staff examples of EDTA contamination in the laboratory and made an awareness campaign to decrease this frequent pre-analytical error. Finally, we evaluated the effect of our campaign. The study was carried out in different services of Charles Nicolle hospital from 1 January to 7 May 2014. We included all paramedical staff who were regularly involved in sample collection for laboratory investigation in those services. A total cohort of 100 subjects was enrolled. First, we detected pre-analytical errors due to EDTA contamination in those services from 1 January to 31 March 2014. Then we handed out an anonymous knowledge assessment to the paramedical staff (see the supplemental data that accompany the article at http://www. degruyter.com/view/j/cclm.2015.53.issue-1/issue-files/ cclm.2015.53.issue-1.xml, Figure 1). After the analysis of cohort responses, we gave the medical and paramedical staff examples of EDTA contamination that occurred in the hospital and investigated in the laboratory: many cases of Brought to you by | Karolinska Institute Authenticated Download Date | 5/23/15 6:06 AM e10 Bouzid et al.: An awareness campaign can decrease pre-analytical errors of EDTA contamination Figure 1 Example of gross EDTA contamination leading to spurious hyperkalemia, hypocalcemia, and hypomagnesemia. patients having two assays (blood count and routine biochemistry parameters) presented EDTA contamination by syringe tip (Figure 1). Finally, all the staff received an awareness campaign for 1 week. At the end, we collected the post-campaign data for 1 month (from 8 April to 7 May). The awareness campaign included clinico-pathological conferences for doctors and nurses, providing evidence-based recommendations for daily practice in phlebotomy with comments on electrolyte reports from examples drawn by biologists in the post-analytical phase (Figure 1). We also posted notices in places where phlebotomies are carried out. EDTA contamination was defined as the presence of hyperkalemia (when serum potassium was over 5.8 mmol/L), hypocalcemia (when serum adjusted calcium was <2.00 mmol/L), and hypomagnesemia (when serum magnesium was <0.66 mmol/L) with normal renal function. For detection of EDTA contamination, calcemia was determined in all samples of hyperkalemia even when not requested by doctors. In addition, for samples with hypomagnesemia, potassium was determined even when not requested. The methods of plasma potassium, calcium, and magnesium measurement used were ionselective electrode, Arsenazo-III, and Arsenazo on the Architect c8000 analyzer, respectively (Abbott Diagnostics, Abbott Park, IL, USA). We had the informed consent of all the hospital services’ head and paramedical staff involved in the study. Data were analyzed by SPSS 11.5. The frequency of EDTA contamination was defined as the percentage of hyperkalemia due to EDTA contamination out of all cases of Brought to you by | Karolinska Institute Authenticated Download Date | 5/23/15 6:06 AM Bouzid et al.: An awareness campaign can decrease pre-analytical errors of EDTA contamination hyperkalemia whatever the cause. χ2-Test was used for the comparison of frequencies before and after the awareness campaign; p<0.05 was taken as significant. The average age of the cohort was 29.5±6.59 years (19–54 years). This cohort comprised 63 nurses, 27 nursing aides, and 10 laboratory technicians. The average seniority in job was 11 years (5–30 years). The frequency of phlebotomy was 4 times a day in 35% of cases, about 5–10 times a day in 55% of cases, and more than 10 times a day in 10% of cases. Among the paramedical staff, 79% do not know the recommended order of draw and only 7% have responded correctly to this order of draw. The remaining 14% have not responded to the assessment. Similarly, for the question concerning the result of an EDTA contamination, 70% gave an incorrect answer, 18% did not respond, and only 12% made a correct answer. In practice, the frequency of EDTA contamination before the awareness campaign and 1 month after decreased from 44.4% to 27.0%, as shown in Table 1. This reduction in frequency of EDTA contamination was statistically significant (p=0.024). Many studies have worked on EDTA contamination, but only our study and that of Ijaz et al. [5] evaluated the effect of an awareness campaign on this pre-analytical error. In our study, we focused on three tests affected by EDTA: potassium, calcium, and magnesium. This gross potassium EDTA contamination of blood samples is easily recognized especially when unexpected hyperkalemia and/or hypocalcemia and hypomagnesemia are found. However, subtle contamination, which is relatively common, is an unrecognized erroneous cause of spurious hyperkalemia [4]. It is also important to know that, sometimes, specimen contamination with potassium EDTA can result into situations more difficult to identify: the same factors causing pseudohyperkalemia can mask hypokalemia by pushing the measured potassium of a hypokalemia patient into the reference interval [3]. By analogy, we can also have cases with masking of true hypercalcemia or hypermagnesemia. This subtle EDTA contamination was studied by Sharratt et al. [4], who had measured EDTA in serum samples. e11 In addition, in cases of patients with renal failure, hyperkalemia and hypocalcemia are common findings, but it is difficult to pick up a potassium EDTA contamination in those patients without measuring serum EDTA. In fact, Davidson has described EDTA assay in specimens; this method is more reliable but requires expensive reagents that are neither suitable for our analyzer nor for another setup [5, 6]. Therefore, when we have to collect more than one tube, special attention has to be given to the order of draw to avoid EDTA sample contamination, inaccurate reports, and patient mismanagement [7]. In fact, laboratories should follow international guidelines regarding procedures for collection of diagnostic blood specimens by venipuncture. The draw order recommended by the Clinical Laboratory Standards Institute, the Croatian Society of Medical Biochemistry and Laboratory Medicine, and the World Health Organization is as follows: blood culture bottle, non-additive tube, coagulation tube, clot activator tube, serum separator, lithium heparin tube, EDTA tube, and oxalate/fluoride tube [2, 8]. However, according to Cornes et al. [9], when using a closed blood collection system, the incorrect draw order of blood samples did not cause EDTA sample contamination. In a similar way, in 2013, Salvagno et al. [8] have found no carryover of additives (e.g., EDTA) between different blood tubes using the Terumo Venosafe blood collection devices. We should be careful to extrapolate their results because we do not use these blood collection systems in our hospital. We can prevent errors during the collection process by diligent application of quality control and continuing education. In fact, the low percentage of paramedical staff who have responded correctly to the anonymous questionnaire (7%) explains the high frequency of EDTA contamination identified by the laboratory (44.4%). However, our study is consistent with a previous study reporting the positive effect of an awareness campaign on EDTA contamination [5]. Thus, the frequency of EDTA contamination was significantly reduced to 27%, demonstrating the importance of the recommended order of draw of blood. Finally, because laboratory test results are the basis for a large proportion (60%–80%) of medical decisions, Table 1 Frequency of EDTA contamination identified by the laboratory before and after the awareness campaign. Before awareness campaign, 1 January to 31 March 2014 After awareness campaign, 8 April to 7 May 2014 Total cases of hyperkalemia EDTA contamination, n (percentage) Total cases of hyperkalemia EDTA contamination, n (percentage) 297 132 (44.4) 48 13 (27.0)a a Significantly different from the percentage before awareness campaign, with p<0.05. Brought to you by | Karolinska Institute Authenticated Download Date | 5/23/15 6:06 AM e12 Bouzid et al.: An awareness campaign can decrease pre-analytical errors of EDTA contamination ensuring the credibility of results is of utmost importance [2]. Education regarding correct blood collection technique is essential in preventing EDTA sample contamination. This involves the correct order of draw of blood samples [10]. Our experience of the awareness campaign providing evidence-based recommendations for daily practice in phlebotomy aimed to improve the quality of patient care. Errors during the collection process are neither inevitable nor can they be eradicated, but they can be reduced by good practices, compliance with the new strategies for error prevention, and continuing education [4, 10]. In conclusion, the continuous training of the paramedical staff with regard to the effects of pre-analytical interferences is a mandatory task in every modern clinical laboratory and hospital [7]. Evaluating their awareness about pre-analytical phase permits to determine related issues that need improvement. Acknowledgments: We thank Pr Zouari Bechir for his help in statistical analysis and the professeurs Dziri Chedly, Bouhajja Bechir, Najjar Taoufik, Baccar Hedi, Marrakchi Zahra, and Khalfallah Narjes as well as their medical and paramedical staff who accepted the collaboration with our laboratory in order to reduce pre-analytical errors. Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission. Financial Support: None declared. Employment or leadership: None declared. Honorarium: None declared. Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication. References 1. International Organization for Standardization. ISO 15189:2012:medical laboratories: particular requirements for quality and competence. Geneva, Switzerland: International Organization for Standardization, 2012. 2. Nikolac N, Supak-Smolcić V, Simundić AM, Celap I. Croatian Society of Medical Biochemistry and Laboratory Medicine: national recommendations for venous blood sampling. Biochem Med (Zagreb) 2013;23:242–54. 3. Asirvatham JR, Moses V, Bjornson L. Errors in potassium measurement: a laboratory perspective for the clinician. North Am J Med Sci 2013;5:255–9. 4. Sharratt CL, Gilbert CJ, Cornes MC, Ford C, Gama R. EDTA sample contamination is common and often undetected, putting patients at unnecessary risk of harm. Int J Clin Pract 2009;63:1259–62. 5. Ijaz A1, Maqsood-ul-Hassan, Khan IM, Saeed F, Tariq KM. EDTA contamination in laboratory specimens – effect of an awareness campaign. J Coll Physicians Surg Pak 2010;20:405–7. 6. Davidson DF. EDTA analysis on the Roche MODULAR analyser. Ann Clin Biochem 2007;44:294–6. 7. Lima-Oliveira G, Lippi G, Salvagno GL, Montagnana M, Picheth G, Guidi GC. Incorrect order of draw could be mitigate the patient safety: a phlebotomy management case report. Biochem Med (Zagreb) 2013;23:218–23. 8. Salvagno G, Lima-Oliveira G, Brocco G, Danese E, Guidi GC, Lippi G. The order of draw: myth or science? Clin Chem Lab Med 2013;51:2281–5. 9. Cornes MP, Sulaiman RA, Whitehead SJ, Othonos N, Ford C, Gama R. Incorrect order of draw of blood samples does not cause potassium EDTA sample contamination. Br J Biomed Sci 2012;69:136–8. 10. Cornes MP, Davidson F, Darwin L, Gay C, Redpath M, Waldron JL, et al. Multi-centre observational study of spurious hyperkalaemia due to EDTA contamination. Clin Lab 2010;56:597–9. Supplemental Material: The online version of this article (DOI: 10.1515/cclm-2014-0686) offers supplementary material, available to authorized users. Brought to you by | Karolinska Institute Authenticated Download Date | 5/23/15 6:06 AM