Performance evaluation of presepsin using a Sysmex HISCL-5000 analyzer and determination of reference interval.

BACKGROUND: Analytical evaluation of newly developed presepsin by a Sysmex HISCL-5000 (Sysmex, Japan) automated immune analyzer was performed. METHODS: For evaluation, sepsis patient samples were collected before treatment in an emergency department. Precision, linearity, limit of blank/limit of detection, method comparisons, and reference intervals were evaluated. Method comparisons were performed using a PATHFAST immune analyzer (LSI Medience Corporation, Japan). RESULTS: Precision using a 20x2x2 protocol for low (306 pg/mL) and high (1031 pg/mL) levels resulted in within-laboratory standard deviation (95% confidence interval [CI]) and coefficient of variation (CV) %, which were as follows: 15.3 (13.1-18.7), 5.5% and 47.7, (40.5-58.1), 6.4%, respectively. Linearity using patient samples and calibrators were measured from 201 to 16,177 and 188 to 30,000 pg/mL, respectively. The regression equation was y = -23.2 + 1.008x (SE = 162.4) for low levels and y = 779.9 + 1.006x (SE = 668) for high levels. Method comparison by Passing-Bablock analysis was as follows: y = -209.77 + 1.047x (Syx  = 335.3). The correlation coefficient (95% CI) was 0.869 (0.772-0.927) with statistical significance (p < 0.001). Reference intervals from 120 normal healthy subjects showed that 300 pg/mL was the cut off. Presepsin tended to show a higher value at higher ages and in males. Presepsin showed correlation with some parameters, and the correlation coefficient (p value) were as follows: hematocrit, 0.198 (0.03); eGFR (CKD-EPI), -0.240 (0.0129); MDRD-eGFR, -0.194 (0.048), respectively. CONCLUSION: Presepsin measurement by HISCL-5000 showed reliable performance. Further clinical studies are required for the diagnosis and prognosis of sepsis.

Evaluation of R-FIND SARS-CoV-2 Neutralizing Antibody ELISA and FREND COVID-19 SP Rapid Fluorescence Immunoassay.

BACKGROUND: Serology testing is useful to determine the past infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: We evaluated the comparative performance of a newly developed neutralizing antibody test (R-FIND SARS-CoV-2 Neutralizing Antibody ELISA, SG Medical, Seoul, Korea) and a rapid fluorescence immunoassay (FREND™ COVID-19 SP, NanoEntek, Hwaseong, Korea) for the detection of SARS-CoV-2 spike protein antibody. They were compared with cPass™ SARS-CoV-2 Neutralization Antibody Detection Kit (Genscript Biotech, Piscataway, NJ, USA) and ADVIA Centaur SARS-CoV-2 Total (COV2T) (Siemens Healthineers, Erlangen, Germany). Forty COVID-19 samples and 80 negative samples were collected after nucleic acid tests. RESULTS: The positive percent agreement (%) of the kit in samples from 6 - 7 days, 8 - 14 days, and 15 - 45 days after symptom onset were as follows: R-FIND (83.3, 76.9, 95.2), cPass (83.3, 69.2, 90.5), FREND (66.6, 84.6, 100), and COV2T (66.6, 69.2, 76.2). The negative percent agreement (%) was 100, 97.5, 92.5, and 100 for R-FIND, cPass, FREND, and COV2T. The total agreement rate between the neutralizing antibody kits (R-FIND and cPass) was 96.7%. FREND showed high agreement with two neutralizing antibody kits (96.7% for R-FIND and 93.3% for cPass). CONCLUSIONS: R-FIND Neutralizing Antibody and FREND COVID-19 SP showed comparable detecting ability to commercial tests.

Evaluating Diagnostic Tests for Helicobacter pylori Infection Without a Reference Standard: Use of Latent Class Analysis.

Evaluation of diagnostic tests requires reference standards, which are often unavailable. Latent class analysis (LCA) can be used to evaluate diagnostic tests without reference standards, using a combination of observed and estimated results. Conditionally independent diagnostic tests for Helicobacter pylori infection are required. We used LCA to construct a reference standard and evaluate the capability of non-invasive tests (stool antigen test and serum antibody test) to diagnose H. pylori infection compared with the conventional method, where histology is the reference standard. A total of 96 healthy subjects with endoscopy histology results were enrolled from January to July 2016. Sensitivity and specificity were determined for the LCA approach (i.e., using a combination of three tests as the reference standard) and the conventional method. When LCA was used, sensitivity and specificity were 83.8% and 99.4% for histology, 80.0% and 81.9% for the stool antigen test, and 63.6% and 89.3% for the serum antibody test, respectively. When the conventional method was used, sensitivity and specificity were 75.8% and 71.1% for the stool antigen test and 77.7% and 60.7% for the serum antibody test, respectively. LCA can be applied to evaluate diagnostic tests that lack a reference standard.

Analytical evaluation and clinical application of insulin and C-peptide by a whole blood, lateral flow, point of care (POC) assay system.

The analytical performance and clinical application of measuring insulin and connecting peptide (C-peptide) by point of care (POC) assay were evaluated. A POC assay system (SelexOn, Osang Healthcare Inc., Anyang-si, Korea) was evaluated for precision, linearity, limit of blank (LOB), and limit of detection (LOD). Method comparison was performed with the Cobas Elecsys insulin and C-peptide assay (Roche Diagnostics GmbH, Mannheim, Germany) using 215 and 201 patient specimens for insulin and C-peptide, respectively. For clinical application, insulin resistance indices were studied. Homeostasis model assessment (HOMA) 1 and 2, Quantitative insulin sensitivity check index (QUIKI), fasting insulin resistance index (FIRI), and other indices were evaluated. The coefficient of variation (CV) of imprecision for low, medium, and high concentrations was 10.8%1, 15.99%, and 12.05%, respectively, for insulin and 9.21%, 13.51%, and 13.77%, respectively, for C-peptide. The linearity was validated to 839.78 pmol/L for insulin and to 17.30 nmol/L for C-peptide. LOB and LOD were 8.05 and 9.72 pmol/L for insulin and 0.05 and 0.08 nmol/L for C-peptide, respectively. For the method comparison, the regression equation was y = 1.259x - 8.818 (r = 0.957) for insulin and y = 1.163x - 0.088 (r = 0.985) for C-peptide. The ROC value and overall accuracy were as follows: HOMA2 (C-peptide), 0.809, 79.7%; TyG, 0.788, 73.6%; CPR, 0.775, 74.8%; HOMA1, 0.725, 70.3%; QUIKI, 0.720, 70.3%; FIRI, 0.715, 70.1%; McAuley, 0.658, 65.1%; HOMA2 (Insulin), 0.645, 64.7%; Raynaud, 0.611, 61.4%, respectively. The POC assay system for insulin and C-peptide provided reliable results through a rapid and simple test that could be applied to clinical settings.

Diagnosis of Liver Fibrosis With Wisteria floribunda Agglutinin-Positive Mac-2 Binding Protein (WFA-M2BP) Among Chronic Hepatitis B Patients.

BACKGROUND: Wisteria floribunda agglutinin-positive Mac-2 binding protein (WFA-M2BP) is a protein with altered glycosylation that reacts with lectin, and was recently identified as a useful non-invasive biomarker for the diagnosis of liver fibrosis in patients with hepatitis C virus infection.This study aimed to evaluate the diagnostic efficacy of WFA-M2BP for liver fibrosis in the context of hepatitis B virus (HBV). METHODS: We enrolled 151 patients infected with HBV. Liver biopsy and elastography (Fibroscan) were performed during the initial visit. Fibrosis was graded according to the Knodell histologic activity index (F0-3). WFA-M2BP levels were determined with an automated immunoassay analyzer (M2BPGi, HISCL-5000, Sysmex, Japan). The diagnostic efficacy of WFA-M2BP was compared with those of various conventional or composite biomarkers, including enhanced liver fibrosis (ELF) score, Fibroscan, aspartate transaminase (AST)-to-platelet ratio index (APRI), and FIB-4, based on the area under the ROC curve (AUC) value. RESULTS: The majority of patients were at fibrosis stages F1 and F2. The F2 and F3 AUC values for WFA-M2BP were similar to those for FIB-4, APRI, ELF, and Fibroscan, although the latter showed the best diagnostic efficacy. The diagnostic accuracy of all tested biomarkers for F2 and F3 was 60-70%. In multivariate analysis, WFA-M2BP, ELF, and platelet count significantly predicted stage ≥F2, whereas only platelet count significantly predicted F3. CONCLUSIONS: WFA-M2BP can support a diagnosis of liver fibrosis with similar diagnostic efficacy to other biomarkers, and predicted liver fibrosis stage ≥2 among patients with chronic hepatitis B.