Journal of Applied Laboratory Medicine最新文献

Background: Liquid chromatography tandem mass spectrometry (LC-MS/MS) is a highly sensitive analytical tool that has become the gold standard for measuring the concentrations of some steroidal hormones and therapeutic drugs in blood. However, the application of this technology in different clinical laboratories faces challenges related to the preanalytical process. In this study, we investigated how the materials used in blood collection tubes affect the measurement of serum 25-hydroxyvitamin D [25(OH)D] by LC-MS/MS.

Methods: Serum samples were collected in 20 different blood collection tubes made by various manufacturers. The samples were processed under controlled conditions to simulate clinical practice, followed by measurement using an LC-MS/MS system. The data were compared with measurements obtained from a chemiluminescent enzyme immunoassay.

Results: Significant variability in measurement outcomes was observed depending on the type of blood collection tube used. Specific blood collection tubes from a manufacturer that employed specific separator gels exhibited interference, as indicated by broad peaks in chromatograms. This interference complicated the quantification of 25(OH)D. The interference was consistent across multiple samples, indicating a systemic problem related to the materials used in the blood collection tubes.

Conclusions: These findings highlight the need to evaluate blood collection tubes from various manufacturers prior to the clinical implementation of LC-MS/MS measurements. Because LC-MS/MS has unique potential error sources, our results indicate the importance in utilizing LC-MS/MS international standards to ensure accurate and reliable results in clinical laboratories.

Background: We sought to determine the prevalence, clinical impact, neutralizing capacity, and cross-reactivity of pre-existing antibodies to infliximab and adalimumab in antitumor necrosis factor (TNF) treatment-naïve patients with active luminal crohn disease.

Methods: The prevalence of antibodies to infliximab and adalimumab at entry to the "Personalised Anti-TNF Therapy in Crohn's Disease Study" (PANTS) were measured using the drug-tolerant IDKmonitor Total antidrug antibody ELISAs. Neutralizing capacity in positive cases was determined using iLite™ cell-based assays.

Results: Pre-existing antibodies to infliximab were more common (6.3%, 96/1525 vs 2.4%, 36/1525, P < 0.01) and detectable at higher concentrations [median (IQR) 23.9 (14.2-55.2) AU/mL vs 7.2 (6.3-10.4) AU/mL, P < 0.0001] to infliximab than adalimumab. A few patients [1.3% (95% CI 0.6-1.8) 20/1525] had antidrug antibody reactivity to both drugs. None of the detected antidrug antibodies had demonstrable anti-TNF neutralizing capacity. No associations were seen between pre-existing antibody positivity, adverse drug reactions, drug levels, or response status at weeks 14 or 54 or subsequent immunogenicity. Cross-reactivity with rheumatoid factor and antimouse antibodies was detected (>10 IU/mL) in 6.6% (95% CI 3.2-13.0) (7/106) and 17.0% (95% CI 10.5-25.2) (19/112) of patients with pre-existing antibodies.

Conclusions: Pre-existing antidrug antibodies are common but do not neutralize anti-TNF drug activity in vitro, promote drug clearance, or influence clinical response to anti-TNF drugs. Further work is required to understand this cross-reactivity and to determine the exact nature of the antibodies detected in drug-naïve individuals.

Background: Aging is associated with subclinical changes in cardiac structure and function as well as an increase in prevalent cardiovascular disease and geriatric syndromes such as frailty and sarcopenia. This can result in levels of cardiac-specific and non-cardiac-specific circulating biomarkers that are frequently above normal range concentrations established in healthy middle-age general population cohorts in the absence of acute disease. Without this recognition, clinicians may be challenged to interpret biomarker results in older adults in the setting of diagnosing an acute illness or for longer term prognostication.

Content: In this review, we provide anticipated findings, their suggested underlying mechanism, as well as interpretation of concentrations for the common cardiovascular biomarkers including cardiac troponins and natriuretic peptides in the acute care and ambulatory settings. Specifically, information to interpret biomarkers in the setting of possible acute myocardial infarction and heart failure is presented. We also present data for interpreting results in older adults with other well-known prognostic biomarkers, as well as biomarkers with application to geriatric syndromes.

Summary: Circulating biomarkers, despite challenges in interpretation in older adults relative to younger adults, play a critical role in the diagnosis and prognosis of cardiovascular disease and have additional roles in geriatric syndromes and assessing risk of harm from specific treatments.

Background: Not all quantity values determined in a medical laboratory are obtained by direct analytical measurement. In many situations, a quantity value is calculated from other measurements through a functional relationship, where the output quantity is derived from one or more input quantities by applying a defined mathematical equation. Even though important for clinical interpretation, the measurement uncertainty (MU) of calculated quantities may not always be considered.

Content: The prostate health index (phi) has been shown to improve the clinical assessment of prostate cancer. Estimates for the MU of phi have been recently provided by a novel approach in which the uncertainty of phi was directly calculated from internal quality control (IQC). However, this method for determining MU generally provides a higher estimate than the procedure recommended by the "Evaluation of Measurement Data-Guide to the Expression of Uncertainty in Measurement" (GUM) and does not allow for the incorporation of a correlation term. A full evaluation of the MU for phi by the GUM procedure is provided.

Summary: The importance of the GUM approach with the inclusion of correlation terms is clearly shown by the phi calculation. By comparison, the relative standard uncertainty obtained by the direct IQC procedure for a mean phi value of 24.48 was given as 7.2%, while by GUM, the relative standard uncertainty for the same mean phi was 3.60% with correlation included and 5.99% without correlation. The influence of correlation terms within the GUM equations is clearly shown for the phi calculation.

Background: Fluid pH remains a standard test when evaluating pleural effusions. Studies recommend using a blood gas analyzer to measure fluid pH immediately after sample collection. Centralization of laboratory services at our institution led to migration of blood gas analysis to a single core laboratory with uncertain impacts on pH results.

Methods: Pleural fluid samples were obtained from 30 patients during routine clinical care, excluding those with frank purulence or blood. Fluid pH and pCO2 were measured on a blood gas analyzer. We compared samples collected in plastic screw-top vials from commercially available thoracentesis kits vs paired samples collected in blood gas syringes. We also examined how differences in processing time, fluid pCO2, and heparin anticoagulant correlated with measured pH.

Results: Of the 30 paired samples obtained, 25 (83.3%) were exudates and 5 (16.7%) were transudates. All samples collected in blood gas syringes had lower mean pH and higher mean pCO2 than samples collected in plastic screw-top vials (mean pH difference ± SD, 0.16 ± 0.06; P < 0.001) (mean pCO2 difference ± SD, 14.09 ± 6.92; P < 0.001). Differences in fluid pH were independent of total nucleated cell count (range 65-28 380 cells/mm3). Neither the presence of heparin in the syringe nor time delays up to 2 h between collection and analysis meaningfully impacted the pH result (P = 0.51 and P = 0.75, respectively).

Conclusion: To accurately measure pleural fluid pH, specimens should be collected anaerobically in blood gas syringes rather than the screw-top vials provided in thoracentesis kits.

Background: While clinical laboratories routinely perform automated chemistry assays on approved specimens (e.g., plasma and serum), the FDA has not evaluated the validity of these assays for nonapproved specimens (e.g., various body fluids). To meet College of American Pathologists' regulatory requirements, clinical laboratories must evaluate body fluid matrix effects. However, full validation studies are challenging due to time and labor demands. Therefore, a rapid and practical approach for validating body fluids benefits clinical laboratories by improving efficiency and minimizing resources utilized.

Methods: Excess body fluids and plasma specimens were collected and frozen until testing was performed. Pooled body fluid specimens were spiked with a 10% spike solution (pooled plasma) containing analyte mixtures with measured concentrations. Matrix interference studies and dilution studies were performed on the Roche cobas automated (6000/8000) analyzers.

Results: The matrix effects for albumin, amylase, blood urea nitrogen, cholesterol, creatinine, glucose, lactate, lactate dehydrogenase, lipase, potassium, sodium, total bilirubin, total protein, triglycerides, and uric acid were all within acceptable limits (±20% of full recovery). However, lipase was observed to be unstable in peritoneal fluid. Dilution linearity was confirmed for all analytes in pleural, peritoneal, ascites, and synovial fluids (R2 > 0.90).

Conclusions: Our study describes a rapid and practical approach for evaluating body fluid matrix effects in automated clinical chemistry assays. By streamlining the validation process, this approach can help laboratories maintain compliance while minimizing time and resources.

Background: Elevated concentrations of the glycoprotein soluble urokinase plasminogen activator receptor (suPAR) predict worse cardiovascular disease (CVD) outcomes. However, glycosylation effects on its measurement are unknown.

Methods: Plasma samples were obtained from healthy volunteers (n = 70), patients with and without myocardial infarction (MI) from an acute chest pain cohort (n = 65), and patients with and without acute decompensated heart failure (ADHF) from an acute breathlessness cohort (n = 103). After the addition of either deglycosylation enzymes or a diluent to paired samples from each patient, subsequent measurements for suPAR were undertaken with the suPARnostic assay. Percentage change in concentrations between enzyme-treated and matched nontreated samples was calculated. MI and ADHF discrimination by receiver operating characteristic area under the curve was used to compare performances of nontreated suPAR vs deglycosylated suPAR.

Results: Following deglycosylation, measured suPAR concentrations are increased by a median of 52.8% (from 1.9 to 3.0 ng/mL, P < 0.0001) in healthy subjects. Similar increases for deglycosylated suPAR were observed in MI (53.6%) and non-MI acute chest pain patients (53.3%). Although acutely breathless patients obtained smaller increases in deglycosylated suPAR values than healthy individuals (P < 0.0001), the percentage increase was higher in ADHF (38.6%) compared to non-HF (24.4%, P = 0.002) patients. ADHF discrimination was superior for deglycosylated suPAR than non-treated suPAR (0.850 vs 0.765, P = 0.003), but no differences were observed for MI discrimination (0.485 vs 0.501, P = 0.508).

Conclusions: Glycosylation underestimates suPAR measurement using the suPARnostic assay. Although glycosylation effects varied across patient groups, removal of suPAR glycosylation appears to enhance heart failure discrimination.