Clinical Chemistry

We measured apolipoproteins (apo) A-I and B by rate immunonephelometry (rate INA) during Phase 1 of the National Health and Nutrition Examination Survey (NHANES) III. We also made the measurements by radial immunodiffusion (RID) in a 20% subset of the samples. Aliquots of this subset were also analyzed in the Northwest Lipid Research Laboratories by fixed-time INA calibrated to the World Health Organization (WHO)-International Federation of Clinical Chemistry (IFCC) First International Reference Materials for Apolipoproteins A-I and B. The CVs for the rate INA and RID measurements were: apoA-I, 4.5-7.7% and 2.5-7.6%, respectively; apoB, 2.3-5.3% and 2.3-6.4%, respectively. In NHANES III, rate INA values (x) can be transformed to WHO-IFCC Reference Material-based values (y) as follows: for apoA-I, y = 0.87x + 251.8 mg/L (r = 0.93, SEslope = 0.13, SEintercept = 17, n = 708); for apoB (mg/L), y = 1.068x + 112.8 mg/L (r = 0.98, SEslope = 0.08, SEintercept = 7, n = 646).

Orotic acid (ORA) is an important biochemical marker for uridine monophosphate synthase deficiency, an autoso-mal recessive disease characterized by macrocytic hypo-chromic megaloblastic anemia, growth retardation, orotic aciduria, and crystalluria (1). In addition, patients with urea cycle diseases excrete increased amounts of urinary ORA (2). Thus, ORA aciduria is observed in patients with ornithine carbamoylasetransferase deficiency (OCTD), an X-linked disorder, and could reveal heterozygosity after a protein load, and in citrullinemia, argininosuccinic acid-uria, and argininemia (2, 3). Currently there are two widely accepted approaches to the determination of urinary ORA, stable-isotope-dilution gas chromatography–mass spectrometry (GC/MS), and ion-exchange HPLC methods with ultraviolet detection,

BACKGROUND High-sensitivity cardiac troponin T (hs-cTnT) is a biomarker used in diagnosing myocardial injury. The clinical utility and the variation of this biomarker over time remain unclear in hemodialysis (HD) and peritoneal dialysis (PD) patients. We sought to determine whether hs-cTnT concentrations were predictive of myocardial infarction (MI) and death and to examine hs-cTnT variability over a 1-year period. METHODS A total of 393 nonacute HD and PD patients (70% HD and 30% PD) were followed in a prospective observational study for new MI and death. RESULTS Median hs-cTnT was 57 ng/L (interquartile range, 36–101 ng/L) with no observed difference between HD and PD patients (P = 0.11). Incremental increases in mortality (P = 0.024) and MI (P = 0.001) were observed with increasing hs-cTnT quartiles. MI incidence increased significantly across quartiles in both HD and PD patients (P = 0.012 and P = 0.025, respectively), whereas mortality increased only in HD patients (P = 0.015)....

The first generation of troponin T ELISA (TnT 1) can yield false-positive results in patients with severe skeletal muscle injury. Therefore, a cardiac-specific second-generation troponin T ELISA (TnT 2) was developed, in which the cross-reactive antibody 1B10 has been replaced by a high-affinity cardiac-specific antibody M11.7. No cross-reactivity of TnT 2 was observed with purified skeletal muscle troponin T (1000 micrograms/L) or in test samples from 43 marathon runners and 24 patients with rhabdomyolysis and highly increased creatine kinase. TnT 2 was increased > 0.2 microgram/L in 5 of 40 patients with renal failure and in 4 of 20 muscular dystrophy patients. The detection limit is 0.012 microgram/L. Day-to-day imprecision (CV) within the range 0.19-14.89 micrograms/L was < 5.8%. In 4955 patients without myocardial damage, 99.6% had TnT < 0.10 microgram/L. Assay comparison (TnT 1 vs TnT 2) over the whole concentration range (i.e., in 323 samples from AMI-suspected patie...

Colorectal carcinoma is the third most common cancer in the United States. Proper and standardized pathologic staging is vital for prognostic assessment and impacts therapeutic decisions. The Tumor Node Metastasis (TNM) staging system was developed by the American Joint Committee on Cancer (AJCC) to be a data-driven, evidence-based staging system providing an accurate prediction of outcome. The AJCC 7th edition (2010) included several changes clarifying some issues and leading to new controversies. We aim to address selected challenging issues in tumor T staging, neoadjuvant treatment effects in rectal cancer, and definition of lymph node vs tumor deposit. Serosal involvement in colorectal cancer is staged as T4, which is associated with decreased survival and may impact additional therapy decisions. Although careful sampling and sectioning are helpful, challenges remain in interpretation of tumor within 1 mm of serosal surface with a reaction. Elastic stain as a surrogate marker fo...

We studied the changes in blood glucose concentration in blood samples collected in heparinized specimen tubes containing no other preservative, or containing NaF, D-mannose, or a combination of NaF and D-mannose. Blood concentration in samples taken into NaF decreased by 0.40 mmol/L in the first 2 h; thereafter, there was no change. In samples collected into mannose there was a small but significant decrease in blood glucose concentration with time. When samples containing mannose were analyzed immediately after collection, the concentration of glucose was higher than in later analyses, probably because of an exchange of intracellular glucose for extracellular mannose. When a combination of NaF and mannose was used, the blood glucose concentration was relatively stable but slightly higher than nonpreserved samples for the next 24 h. However, samples containing mannose were unsuitable for electrolyte analysis. We conclude that a combination of D-mannose and NaF may be a better prese...

Cancer biomarkers are commonly used in pediatrics to monitor cancer progression, recurrence, and prognosis, but pediatric reference value distributions have not been well established for these markers. The Canadian Laboratory Initiative on Pediatric Reference Intervals (CALIPER) sought to develop a pediatric database of covariate-stratified reference value distributions for 11 key circulating tumor markers, including those used in assessment of patients with childhood or adult cancers. Healthy community children from birth to 18 years of age were recruited to participate in the CALIPER project with informed parental consent. We analyzed serum samples from 400-700 children (depending on the analyte in question) on the Abbott Architect ci4100 and established reference intervals for α-fetoprotein (AFP), antithyroglobulin (anti-Tg), human epididymis protein 4 (HE4), cancer antigen 125 (CA125), CA15-3, CA19-9, progastrin-releasing peptide (proGRP), carcinoembryonic antigen (CEA), squamou...

The ABCA1 gene encodes for a member of subfamily A of the ATP-binding cassette transporters that plays an important role in cellular export of cholesterol and phospholipids; therefore, quantification of the ABCA1 mRNA is critical in many studies related to its expression and regulation by metabolic factors, nutritional status, and new antiatherogenic drug candidates. We developed a rapid, sensitive, specific, and reproducible real-time reverse transcription-PCR (RT-PCR) method for detection and quantification of ABCA1 transcripts in total RNA isolated from cultured human cells and tissues. To quantify ABCA1 mRNA, we generated a calibration curve from serial dilutions of in vitro-transcribed RNA corresponding to an amplified ABCA1 cDNA 205-bp fragment (homologous calibrator). Two pairs of fluorescent hybridization probes were used to detect the ABCA1 and porphobilinogen deaminase (PBGD) mRNAs; the latter served as an internal control. PCR was performed as real-time amplification of A...

BACKGROUND In cancer patients, circulating cell-free DNA (ccfDNA) can contain tumor-derived DNA (ctDNA), which enables noninvasive diagnosis, real-time monitoring, and treatment susceptibility testing. However, ctDNA fractions are highly variable, which challenges downstream applications. Therefore, established preanalytical work flows in combination with cost-efficient and reproducible reference materials for ccfDNA analyses are crucial for analytical validity and subsequently for clinical decision-making. METHODS We describe the efforts of the Innovative Medicines Initiative consortium CANCER-ID (http://www.cancer-id.eu) for comparing different technologies for ccfDNA purification, quantification, and characterization in a multicenter setting. To this end, in-house generated mononucleosomal DNA (mnDNA) from lung cancer cell lines carrying known TP53 mutations was spiked in pools of plasma from healthy donors generated from 2 different blood collection tubes (BCTs). ccfDNA extracti...

We examine the effect of systematic bias and random error, quality control, and intraperson biological varia- tion on the National Cholesterol Education Program (NCEP) clinical classifications for reported lipid mea- surements. We consider misclassification to occur if a true lipid homeostatic set point is within a desirable range but the reported lipid value is in a high-risk range, or if

Background: Saliva is an alternative biologic matrix for drugs-of-abuse testing that offers the advantages of noninvasive, rapid, and easy sampling. We studied the excretion profile of 3,4-methylenedioxymethamphet- amine (MDMA) and its metabolites in both saliva and plasma, as well the effect of the drug on salivary pH. Methods: Saliva and plasma samples were obtained from eight healthy MDMA consumers after