Journal of Applied Laboratory Medicine最新文献

Background: Therapeutic monoclonal antibodies (t-mAbs) may interfere with electrophoresis-based methods used to monitor multiple myeloma (MM), which can create inaccurate results. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry is an alternative to gels distinguishing between endogenous M-proteins and t-mAbs based on molecular mass.

Methods: Serum samples (n = 109) from 34 MM patients receiving Dara-KRd were collected 14 or 28 days postdaratumumab administration. Samples were analyzed using the EXENT® Analyzer that combines automated immunopurification and MALDI-TOF MS for the isotyping and quantification of monoclonal immunoglobulins.

Results: Daratumumab was identified in 103 out of 109 samples (94.5%). In all IgGλ (n = 8), IgAκ (n = 8), and IgAλ (n = 2) patients, the M-protein and daratumumab were detected. Of the IgGκ patients (n = 18), 5 patients had a total of 6 samples where the M-protein was detected but daratumumab was not. There was no difference in the detection rate of daratumumab between samples taken 14 and 28 days postadministration with the median daratumumab concentration being 0.95 and 0.54 g/L, respectively. A precision study was also performed on 25 replicates containing 1 g/L daratumumab in serum where a coefficient of variation of 4.2% was observed as determined by the EXENT Analyzer.

Conclusions: The Immunoglobulin Isotypes (GAM: IgG, IgA, and IgM) for the EXENT Analyzer detected and distinguished a daratumumab kappa light chain peak from an M-protein light chain peak in MM patient serum when resolved by the mass spectrometer.

Background: Rasburicase retains activity at room temperature (RT), so specimens collected for uric acid-level monitoring require cooling protocols. Our objective was to determine if we could ease these preanalytical requirements to improve compliance while maintaining accuracy.

Methods: Fifty pairs of specimens were transported and stored either on ice or at RT. All were tested at 3 time points postcollection: immediately upon arrival to the laboratory (approximately 45 min), 90, and 135 min.

Results: Uric acid concentrations are not clinically significantly different in RT or iced specimens, as long as specimens are tested within approximately 45 min postcollection. There was a negative bias in uric acid levels in a subset of specimens if they were held at RT and tested at 90 min (-9.1%) and 135 min (-17.5%). Specimens tested within 2 rasburicase half-lives postinfusion have an additional 24% decrease in uric acid levels if kept at RT for 90 min. Specimens from patients given a 6 mg dose had an 18% decrease in uric acid concentration compared to a 3 mg dose.

Conclusions: Laboratories that can test uric acid levels rapidly after specimen collection may be able to validate alternative preanalytical methods to transporting and testing on ice.

Background: Hemolysis is a major pre-analytical concern for many laboratory analytes; however, instruments utilized for whole blood chemistries and blood gas measurements lack the ability to detect and measure the degree of hemolysis. This study evaluated the effect of hemolysis on 13 routine whole blood and blood gas analytes and compared visual assessments of hemolysis to measured hemolysis (H-index).

Methods: Remnant whole blood samples (n = 85) were split into 2 portions and aspirated through a syringe one or more times. To induce hemolysis, a needle was affixed to the end of the syringe to provide shear stress, and a mock procedure without syringe was used as a control. Samples were analyzed on a Radiometer ABL800 series instrument, centrifuged, and the H-index of the plasma portion was measured. Two medical technologists recorded a visual categorization of the specimens as slightly, moderately, or severely hemolyzed.

Results: Hemolysis had a modest effect on metabolites and most cooximetry components, with percent bias within ±5% at all levels of hemolysis. Methemoglobin exhibited a larger overall negative bias, up to 13.3%. The absolute pH bias was fairly consistent (within 0.1 pH units) across all levels of hemolysis. As expected, potassium displayed a significant positive bias with increasing hemolysis. Sodium and ionized calcium displayed overall linear trends with a significant negative bias.

Conclusions: Hemolysis can falsely increase or decrease certain blood gas analytes and lead to misinterpretation of results. Therefore, hemolysis detection capabilities are crucial for mitigating this effect and ensuring accurate results for patient care.

Elevated human chorionic gonadotropin (hCG) of unknown etiology is often a diagnostic dilemma. Determination of its source is vital in order to provide proper medical treatment and prevent possible unneeded therapeutic interventions. The differential diagnosis for elevated hCG is broad and includes pregnancy, chronic kidney disease, heterophile antibody, macro-hCG, exogenous hCG administration, pituitary secretion, tumor-associated secretion, etc. One entity that is emerging in the published literature as a cause of elevated hCG is familial hCG syndrome. This syndrome is characterized by persistently elevated concentrations from a yet to be determined source in individuals of the same family. In this special report, we review a recently published case of elevated hCG in a 56-year-old male proposed to be due to familial hCG syndrome. We discuss why we feel the presented case is not consistent with familial hCG syndrome and explore other possible explanations for the patient's elevated hCG concentrations.

Background: Most studies found that apolipoprotein B (apo B)-100 is a superior marker for coronary risk to non-high-density lipoprotein (HDL) cholesterol (C). Usually, studies use multivariant analysis with single-point odds/risk ratios. In multivariant analysis, when variables are highly correlated they are difficult to interpret. Effects cannot be well discriminated.

Methods: Brief review and examination of diagnostic sensitivity and specificity by receiver operator characteristic (ROC) curves at decision levels so that discrimination can be well compared. Since apo B has additional expense, clinical value should be compared in an appropriate format. Apo B and cholesterols were measured in 382 angiographically defined patients.

Results: Non-HDLC and apo B were stronger markers than low-density lipoprotein (LDL)C, when examined by logistic regression, but as a result of strong collinearity, non-HDLC appeared weaker than LDLC in the presence of apo B, based on P values. This was true when analyzed with and without nonlipid risk factors. On ROC analysis, apo B and non-HDLC showed stronger C statistics than LDLC and total C. When analyzed alone apo B showed about 6.1% greater sensitivity than non-HDLC. After adjustment for nonlipid risk factors, the C statistics for apo B and non-HDLC were 0.74 and 0.73, and there was little difference in diagnostic specificity.

Conclusions: Risk is calculated from an algorithm that includes nonlipid risk factors similar to those examined here along with cholesterols. When assessed by the 10-year screening algorithm, these data support the view that non-HDLC would be less expensive than apo B with similar clinical efficacy.

Background: Procalcitonin (PCT) measurement is useful for guiding antibiotic therapy and risk assessment in lower respiratory infections and/or sepsis. This study evaluated clinical and analytical performance of the Vitros® Immunodiagnostic Products B·R·A·H·M·S PCT assay (Vitros PCT).

Methods: Precision, limits of blank (LoB), detection (LoD), and quantitation (LoQ) were determined for Vitros PCT, along with method comparison and clinical concordance with the B·R·A·H·M·S PCT™-sensitive KRYPTOR™ assay (KRYPTOR PCT). All-cause 28-day mortality was evaluated according to the change in PCT values (ΔPCT) from day 0 through day 4 in samples from 598 intensive care unit patients with sepsis.

Results: Comparison of Vitros PCT and KRYPTOR PCT results yielded a Deming regression slope of 1.057, intercept of -0.010, and correlation coefficient (r) of 0.994. Precision analysis demonstrated within-laboratory coefficients of variation for Vitros PCT ranging from 3.1% to 6.4%. The LoD and observed LoQ were determined as 0.007 and 0.013 ng/mL, respectively. Overall agreement between assay methods was 98.5%, 98.0%, 97.4%, and 97.8%, at PCT clinical decision cutoffs of 0.100, 0.250, 0.500, and 2.00 ng/mL, respectively, with Cohen's Kappa coefficients (κ) > 0.91. ΔPCT values ≤80% vs >80% were associated with increased 28-day-all-cause mortality (P = 0.006).

Conclusions: Vitros PCT compares well with KRYPTOR PCT, showing excellent agreement at relevant clinical decision cutoffs that have been used for antibiotic decision-making and assessment of risk for sepsis progression. ΔPCT values determined with Vitros PCT were useful for evaluation of 28-day mortality risk in patients with severe sepsis.

Background: Lateral flow assay (LFA) is a rapid analytical technique that has been implemented as a point-of-care approach for analyte detection. Given the rapid expansion of the use of LFA as a point-of-care testing strategy, LFA development has been subjected to extensive research, which has resulted in upgraded designs and technologies, improving levels of specificity and costs associated with manufacturing. This has allowed LFA to become an important option in rapid testing while maintaining appropriate limits of detection for accurate diagnoses.

Content: This review focuses on the theoretical basis of LFA, its components, formats, multiparametric possibilities, labels, and applications. Also, challenges associated with the technique and possible solutions are explored.

Summary: We explore LFA as a detection technique, its benefits, opportunities for improvement, and applications, and how challenges to its design can be approached.