Journal of Applied Laboratory Medicine最新文献

Background: The diagnosis of laryngopharyngeal reflux disease (LPRD) mostly uses invasive techniques. Our aim was to carry out a performance study of noninvasive saliva biomarkers in LPRD patients and to investigate clinical utility.

Methods: The saliva of 201 patients with an LPRD diagnosis was prospectively collected using a Salivette® device. Findings were compared with 35 healthy controls using nonparametric statistics. Biomarker cut-offs were determined with receiver operating curves (ROCs).

Results: The analytical performance study indicated satisfactory performance against biological acceptability goals for bias, imprecision, and total allowable error. The limit of detection (LOD) was evaluated for all biomarkers in the saliva matrix. Results fell within the analytical measurement range for salivary elastase, trypsin, and pH and close to the LOD for cholesterol. The clinical study reported significantly higher salivary pH and elastase and lower cholesterol in LPRD compared to controls (P < 0.05), while salivary trypsin did not differ significantly. Diagnostic cut-offs determined with ROC were salivary elastase >49 µg/mL, salivary pH >7.6, and salivary cholesterol <2.1 mg/dL (<0.054 mmol/L). The combination of salivary elastase with cholesterol gave a positive predictive value of 93% and a negative predictive value of 100% for the diagnosis of LPRD in this study. Salivary total bilirubin, lipase, and pepsin were mostly undetected.

Conclusions: Noninvasive diagnosis of LPRD is possible, based on a single saliva collection, although our cut-offs should be evaluated in further studies. A reproducible analytical protocol has been obtained. Salivary elastase, cholesterol, and pH show clinical utility for the presence of duodeno-gastric reflux in LPRD patients.

Background: The trace element zinc is essential for multiple biological processes and analyzed in suspected cases of deficiency or toxicity. A systematic approach to abnormal results will aid the diagnosis of a patient with low or high zinc concentration in plasma in a more clinically efficient and cost-effective manner.

Content: True zinc deficiency can be attributed to both acquired and inherited causes; however, falsely low concentrations may be obtained through sample timing, during inflammatory states, and in the presence of certain medications and hypoalbuminemia. High concentrations of zinc may be due to fasting, hemolysis, or environmental contamination of blood test tubes. The clinical status and condition of the patient should be considered to allow a targeted investigation to be carried out.

Summary: Diagnostic flow charts have been created to help aid healthcare professionals to investigate the cause of both low and high zinc concentrations where the cause is not immediately apparent. This article provides a set of algorithms to suggest an investigative strategy in cases of unexpected abnormalities in plasma zinc.

Background: Dipeptidyl peptidase 3 (DPP3) is a peptidase released from dying cells. It cleaves proteins in the renin-angiotensin pathway, which can result in hemodynamic instability. At elevated concentrations DPP3 is associated with worse outcomes, particularly in patients with shock. Herein we describe the assay performance of a DPP3 assay (4TEEN4 Pharmaceuticals GmbH) in human plasma.

Methods: DPP3 concentration was measured using the DPP3 immunoluminometric assay (4TEEN4 Pharmaceuticals GmbH) and the signal was read using a luminometer (Berthold Centro LB963). Analytical performance was established for precision, linearity, accuracy, detection limit, analytical specificity, reference interval, kit lot-to-lot comparison, specimen type, and sample stability.

Results: Limit of detection was verified at 1.6 ng/mL in EDTA plasma with a coefficient of variation (CV) of <10%. Precision studies revealed a CV ≤ 6% at 28.5 ng/mL and 59.4 ng/mL and comparability with a manufacturer performed assay was demonstrated between 7.7 and 195.2 ng/mL. An upper 97.5% limit of 22 ng/mL without age or sex associations was verified in healthy donors. The assay was not susceptible to interference from lipemia or bilirubin. However, measured DPP3 concentrations increased linearly with increasing hemolysis. DPP3 concentrations are stable in EDTA plasma for up to 24 h and at least 11 months when stored ambient or at -80°C, respectively.

Conclusions: DPP3 can be measured precisely in EDTA plasma using the immunoluminometric DPP3 assay. Given the potential clinical use of DPP3 in critical care patients, caution should be taken to avoid inducing pre-analytical hemolysis during sample collection.

Background: Allowable total error (ATE) is a quality concept that defines acceptable analytical performance for a clinical laboratory assay. ATE will vary in terms of the amount of error permissible not only between assays but also based on the test setting and the assay's clinical use. In the clinical laboratory, ATE limits are routinely applied, for example, when evaluating new analytical methodology or equipment for patient testing, troubleshooting unacceptable quality control, or in evaluating instrument comparability.

Content: Currently, there are no universally applicable standards for defining the maximum magnitude of allowable error. However, there are several resources available for users to consider when setting ATE limits. Examples include clinical outcomes studies, biological variation of the measurand, state-of-the-art, professional organizations, and requirements set by regulatory agencies and proficiency testing/external quality assessment scheme organizers. Each of these approaches varies in terms of the resulting magnitude of allowable error for the same assay. This review describes these resources in more detail and discusses the strengths and weaknesses of each approach.

Summary: ATE users should be aware of different resources and their limitations before defining acceptance criteria for an assay in their clinical laboratory.

Background: Urine sediment analysis is a cornerstone of diagnostic testing. This study evaluates FUS-3000 Plus, an automated urine sediment analyzer using advanced imaging and artificial intelligence, to assess its technical performance and diagnostic accuracy for routine clinical use.

Methods: The study analyzed 98 urine samples for chemical parameters (pH, protein, blood, leukocyte esterase, and nitrite) and 76 samples for particle analysis (red blood cells [RBCs], white blood cells, epithelial cells, crystals, bacteria) by both FUS-3000 Plus and sediMAX™, the current laboratory analyzer in use. Additionally, 139 samples were tested for glucosuria and proteinuria, with results compared to the Cobas C702. Carry-over, precision, and linearity were assessed by internal quality controls in accordance with Clinical and Laboratory Standards Institute protocols. Accuracy was further evaluated using external quality controls.

Results: FUS-3000 Plus demonstrated strong agreement with sediMAX for nitrites, protein, and leukocyte esterase (kappa values >0.5) and correlated well with the Cobas C702 for glucosuria and proteinuria. However, discrepancies were observed in glucosuria detection, with some samples yielding inaccurate results even during external quality control assessments. A carry-over effect for RBCs required a rinse step after highly concentrated samples.Precision was acceptable (CV: 3%-11%), and Bland-Altman plots showed strong agreement for formed elements (correlation >0.95). However, the analyzer had reduced accuracy in bacteriuria detection.

Conclusion: FUS-3000 Plus is a reliable tool for routine urinalysis, excelling in particle classification. However, improvements are needed in bacteriuria detection and minimizing carry-over effects. Future research should explore its ability to identify additional cellular elements and its diagnostic utility in diverse clinical populations.

Background: The complete blood count (CBC) is widely used across nearly all areas of medicine. While standard CBC markers reflect basic summaries of the blood cells, modern hematology analyzers generate many additional markers from the underlying data distributions-collectively referred to as cell population data (CPD). While CPD markers have been studied in targeted clinical settings, their value for general prognostic tasks has not yet been established. In this brief report, we assess whether CPD markers can provide additional prognostic information beyond CBC markers in general patient cohorts.

Methods: We retrospectively analyzed CBC and CPD markers from over 10 000 patients at a large academic medical center between March 14, 2024, and October 23, 2024. Marker associations with general outcomes (inpatient admission from the emergency department, mortality, and length-of-stay) were analyzed in both univariate and multivariate models. Outcomes were also predicted using CBC- and CPD-based machine learning models.

Results: Many CPD markers were strongly associated with patient mortality, length-of-stay, and inpatient admission from the emergency department. CPD markers showed consistent outcome associations after stratification by patient demographics and medical specialties, and many retained statistical significance after controlling for commonly used CBC markers. In machine learning modelling, inclusion of CPD markers enhanced predictive performance for mortality [area under the curve (AUC): 0.79] and inpatient admission (AUC: 0.81). Analysis of CPD markers revealed 2 phenotypes: an inflammatory phenotype associated with inpatient admission and a dysregulatory phenotype associated with mortality.

Conclusions: These results highlight how routinely collected CPD markers may enhance the use of the CBC for evaluation of general patient cohorts.

Background: Loperamide is a µ-opioid receptor agonist that reduces intestinal peristalsis and is used to treat diarrhea. We previously described significant cross-reactivity of loperamide with 2 fentanyl immunoassays. Since then, new fentanyl immunoassays, including a CLIA-waived point-of-care device, have been approved for clinical use.

Methods: We evaluated new fentanyl immunoassays for cross-reactivity to loperamide and its major metabolites, N-desmethyl loperamide (dLop) and N-didesmethyl loperamide (ddLop). Previously characterized assays were tested for cross-reactivity to ddLop, which recently became commercially available. Loperamide, dLop, and ddLop were spiked in drug-free urine for analysis by 5 enzyme immunoassays run on automated chemistry analyzers and one lateral flow assay for the detection of fentanyl.

Results: Loperamide and its metabolites produced positive results in 3 fentanyl immunoassays. The Immunalysis HEIA was previously determined to be reactive to both loperamide and dLop, but it was not reactive to ddLop. The Immunalysis SEFRIA was reactive to loperamide, dLop, and ddLop at minimum concentrations of 14.7 mg/L, 13.1 mg/L, and 17.0 mg/L. The Thermo Fisher DRI was previously determined to be reactive to loperamide and dLop, and it was reactive to ddLop at a minimum concentration of 33.1 mg/L. The Abbott iCassette, ARK Fentanyl II, and Lin-Zhi LZI II fentanyl assays showed no cross-reactivity to loperamide or its metabolites.

Conclusions: The cross-reactivity of loperamide, dLop, and ddLop in several fentanyl immunoassays has the potential to cause false-positive results during urine drug screening.