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.

Performance Evaluation of a Point of Care SelexOnTM B-Type Natriuretic Peptide Immunoassay

Background@#This study was conducted to evaluate the analytical performance of the SelexOnTM B-type natriuretic peptide (BNP) assay (Osang Healthcare Inc., Korea), a new rapid lateral flow immunoassay for point of care (POC) testing using whole blood. @*Methods@#The imprecision, linearity, and method comparison of SelexOnTM BNP assay were evaluated. Two commercial BNP assays, the ADVIA Centaur® BNP (Siemens Health Care diagnostics Inc., USA) and the Triage® BNP assays (Alere, USA), were included for method comparison using 100 whole blood samples from patients. The reference interval was verified using 120 residual samples from health examination participants. @*Results@#The SelexOn BNP had total CVs of 20.3%, 13.3%, and 10.3% in BNP concentrations of 89.44 pg/mL, 480.71 pg/mL, and 1,201.84 pg/mL of control materials, respectively. Linearity was observed from 56 pg/mL to 1544 pg/mL. The SelexOn BNP (y) regression equation was y=0.9706x-21.68 with Centaur BNP (x) (r=0.930) and y=0.7600x+0.0506 with Triage BNP (x) (r=0.845), respectively. The predicted mean difference (%) of the SelexOn BNP at the clinical decision levels (100 pg/mL) was up to 25% lower than the two comparative methods. The SelexOn BNP levels were below 50 pg/mL in 114 (95%) of the 120 samples. @*Conclusions@#The SelexOn BNP using EDTA was developed as a POC test for differential diagnosis or treatment monitoring for acute heart failure. However, clinical decision values must be improved to be compatible with other BNP methods.

Usefulness of Reference Change Values for Delta Check Limits in Clinical Laboratory Testing

Background@#In this study, the usefulness of within-subject biological coefficient of variation (CVI) and reference change values (RCVs) for delta check limits were investigated by comparing the population distributionbased delta check limits. @*Methods@#For six tests, including aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase, glucose, creatinine, and hemoglobin, the RCV95%, RCV99%, and RCV99.9% delta limits were obtained. The nonparametric 95% and 99% delta limits were obtained from the population distribution of the delta percentage difference of the health examination group (January 2014 to December 2018) and the outpatient and inpatient groups (January to December 2018). Delta check alerts (%) in total and all three subgroups were examined according to the five different delta check limits. Additionally, we analyzed the correlation of the median CVIF estimates with population-delta check limits for the six tests. @*Results@#The delta percentage difference of the six tests showed a nonnormal distribution, and median value significantly differed among the health examination, outpatient, and inpatient groups (all, P <0.001). The overall delta check alerts of six tests decreased in the order of RCV95%, RCV99%, and RCV99.9%, population distribution -95%, and -99% delta limits; the proportion of the health examination group gradually decreased and that of inpatients increased. A good correlation was observed between median CVI (range, 2.7% to 10.1%) and population distribution delta limits (r =0.96 to 0.99). @*Conclusions@#The RCV delta check limits should be applied differently depending on the health and disease group. CVI can be useful for estimating the delta check limits of the population.

Performance Evaluations of the Abbott Alinity m Assay in Comparison with the Abbott m2000Assay for Hepatitis B and Hepatitis C Viruses

Methods@#The precision, linearity, limit of detection (LOD), correlation with the Abbott m2000 assay, and interference were evaluated. @*Results@#The within-laboratory standard deviation ranged from 0.106 to 0.137 log IU/mL for HBV and from 0.073 to 0.097 log IU/mL for HCV, which was lower than the manufacturer’s specification of 0.25 log IU/mL, indicating good precision. Linearity was observed from 1.14 to 8.14 log IU/mL for the HBV assay and from 1.09 to 7.09 log IU/mL for the HCV assay. The LODs of HBV and HCV were 10 and 6.39 IU/mL, respectively, which were equivalent to or better than those claimed by the manufacturer. For comparative evaluation between Alinity m and m2000 assays, 142 HBV and 70 HCV samples were tested. The correlation test revealed a strong correlation for both markers, and the Passing–Bablok regression analysis did not reveal any significant deviation. @*Conclusions@#The Alinity m assay demonstrated excellent performance for HBV and HCV quantifications with reduced hands-on time and a randomaccess format.

Comparison of Six Commercial Diagnostic Tests for the Detection of Dengue Virus Non-Structural-1 Antigen and IgM/IgG Antibodies

ELISAs and rapid diagnostic tests (RDTs) are widely used for diagnosing dengue virus (DENV) infection. Using 138 single blood samples, we compared the ability to detect non-structural (NS)-1 antigen and anti-DENV IgM/IgG antibodies among (1) DENV Detect NS1 ELISA, DENV Detect IgM capture ELISA and DENV Detect IgG ELISA (InBios International, Inc.); (2) Anti-Dengue virus IgM Human ELISA and Anti-Dengue virus IgG Human ELISA (Abcam); (3) Dengue virus NS1 ELISA, Anti-Dengue virus ELISA (IgM) and Anti-Dengue virus ELISA (IgG) (Euroimmun); (4) Asan Easy Test Dengue NS1 Ag 100 and Asan Easy Test Dengue IgG/IgM (Asan Pharm); (5) SD BIOLINE Dengue Duo (Standard Diagnostics); and (6) Ichroma Dengue NS1 and Ichroma Dengue IgG/IgM (Boditech Med). For NS1 antigen detection, InBios and Euroimmun showed higher sensitivities (100%) than the RDTs (42.9–64.3%). All tests demonstrated variable sensitivities for IgM (38.1–90.5%) and IgG (65.7–100.0%). InBios and Boditech Med demonstrated higher sensitivity (95.6% and 88.2%, respectively) than the other tests for combined NS1 antigen and IgM antibody. Five NS1 antigen tests had good agreement (92.8–98.6%) without showing positivity for chikungunya. However, all IgG tests demonstrated potential false-positivity with variable ranges. Clinical laboratories should note performance variations across tests and potential cross-reactivity.

Serotyping and Antimicrobial Susceptibility of Salmonella Isolated in Korea in 2015 / 대한임상미생물학회지

BACKGROUND: Salmonella is an important pathogen that causes gastroenteritis and sepsis in humans. Recently, changes in serotype prevalence and an increase in antimicrobial resistance have been reported. This study investigated the distribution of Salmonella serotypes and determined the antimicrobial susceptibility of various strains. METHODS: We collected 113 Salmonella isolates other than Salmonella serotype Typhi from 18 university hospitals in 2015. The serotypes were identified by Salmonella antisera O and H according to the Kauffman White scheme. Antimicrobial susceptibility tests for 12 antibiotics were performed using the disk diffusion method or E-test. RESULTS: We identified 22 serotypes. Serotype group B (44.2%) was the most common, followed by groups C (34.5%) and D (21.2%). Salmonella I 4,[5],12:i:- (23.0%), S. Enteritidis (16.8%), and S. Typhimurium (12.4%) were the most common species. Resistance rates for ampicillin, chloramphenicol, ceftriaxone, and trimethoprim/sulfamethoxazole were 46.9%, 18.5%, 8.8%, and 5.3%, respectively. The intermediate resistance rate to ciprofloxacin was 29.2%. Six isolates were extended-spectrum β-lactamase (ESBL) producers, including 5 bla(CTX-M-15) and 1 bla(CTX-M-55). CONCLUSION: There have been changes in the serotype prevalence and antimicrobial resistance of Salmonella in Korea, with a high prevalence of CTX-M 15-positive strains. Continuous monitoring of Salmonella serotypes and antimicrobial resistance is warranted.

Clinical Significance of Inflammatory Biomarkers in Acute Pediatric Diarrhea / 대한소아소화기영양학회지

PURPOSE: The aim of this study was to evaluate the clinical significance of inflammatory biomarkers in acute infectious diarrhea among children. METHODS: Clinical parameters including fever, bacterial and viral etiology based on stool culture and multiplex polymerase chain reaction, and nine biomarkers including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and leukocytes in blood and calprotectin, lactoferrin, myeloperoxidase, polymorphonuclear elastase, leukocytes, and occult blood in feces were evaluated in children who were hospitalized due to acute diarrhea without underlying disease. RESULTS: A total of 62 patients were included. Among these patients, 33 had fever, 18 showed bacterial infections, and 40 patients were infected with 43 viruses. Of all the biomarkers, CRP was significantly correlated with fever (p<0.001). CRP, ESR, calprotectin, lactoferrin, myeloperoxidase, fecal leukocytes, and occult blood were significantly associated with infection with bacterial pathogens (p<0.001, p=0.04, p=0.03, p=0.003, p=0.02, p=0.03, p=0.002, respectively). The combination of CRP and fecal lactoferrin at their best cut-off values (13.7 mg/L and 22.8 µg/mL, respectively) yielded a sensitivity of 72.2%, and a specificity of 95.5% for bacterial etiology compared with their individual use. CONCLUSION: Blood CRP is a useful diagnostic marker for both fever and bacterial etiology in acute pediatric diarrhea. The combination of CRP and fecal lactoferrin yields better diagnostic capability for bacterial etiology than their use alone for acute diarrhea in children without underlying gastrointestinal disease.

Clinical Presentation with High Penetrance in a Korean Family with Pulmonary Arterial Hypertension Associated with a BMPR2 Intron 3 Splice Site Pathogenic Variant

Pathogenic variants of bone morphogenic protein receptor type 2 gene (BMPR2) are related to the majority of cases of heritable pulmonary arterial hypertension (PAH). Over 400 pathogenic variants have been identified. However, clinical characterization of PAH is still incomplete. We present a case of heritable PAH in a Korean family showing serious clinical presentation with high penetrance. Genetic sequencing revealed a known heterozygous BMPR2 pathogenic variant, c.418+5G>A, at a splice site of intron 3. Serious clinical presentation with high penetrance suggested that the interplay of other factors with pathologic variants might be in genotype-phenotype correlation. Further studies are needed to clarify these issues for the development of personalized medicine approaches for PAH.

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.

Comparison of Four Automated Carcinoembryonic Antigen Immunoassays: ADVIA Centaur XP, ARCHITECT I2000sr, Elecsys E170, and Unicel Dxi800

BACKGROUND: Carcinoembryonic antigen (CEA) is one of the tumor markers available for evaluating disease progression status after initial therapy and monitoring subsequent treatment modalities in colorectal, gastrointestinal, lung, and breast carcinoma. We evaluated the correlations and differences between widely used, automated CEA immunoassays at four different medical laboratories. METHODS: In total, 393 serum samples with CEA ranging from 3.0 to 1,000 ng/mL were analyzed on ADVIA Centaur XP (Siemens Diagnostics, Tarrytown, NY, USA), ARCHITECT i2000sr (Abbott Diagnostics, Abbott Park, IL, USA), Elecsys E170 (Roche Diagnostics, Indianapolis, IN, USA), and Unicel DxI800 (Beckman Coulter, Fullerton, CA, USA), and the results were compared. Deming regression, Passing-Bablok regression, and Bland-Altman analyses were performed to evaluate the data correlation and % differences among these assays. RESULTS: Deming regression analysis of data from Elecsys E170 and UniCel DxI800 showed good correlation (y=3.1615+0.8970x). According to Bland-Altman plot, no statistically significant bias (−1.78 ng/mL [95% confidence interval: −4.02 to 0.46]) was observed between Elecsys E170 and UniCel DxI800. However, the relative differences of CEA concentrations between assays exceeded the acceptable limit of 30%. Regarding the agreement of positivity with cut-off value 5.0 ng/mL, ARCHITECT i2000sr and Elecsys E170 showed the highest agreement (95.2%), whereas ADVIA Centaur XP and ARCHITECT i2000sr showed the lowest agreement (70.7%). CONCLUSIONS: Agreements between automated CEA immunoassays are variable, and individual CEA concentrations may differ significantly between assays. Standardization of serum CEA concentrations and further harmonization are needed.

Intactness of Medical Nonsterile Gloves on Use of Alcohol Disinfectants

No abstract available.

Functional Identification of Compound Heterozygous Mutations in the CYP17A1 Gene Resulting in Combined 17α-Hydroxylase/17,20-Lyase Deficiency

BACKGROUND: We previously reported a patient with congenital adrenal hyperplasia (CAH) with compound heterozygous mutations in the cytochrome P450 17A1 (CYP17A1) gene. One allele had a p.His373Leu and the other a new p.Glu383fsX36 mutation. The aim of this study was to investigate the functional properties of a new allele present in a compound heterozygote of CYP17A1. METHODS: To understand how p.His373Leu and p.Glu383fsX36 affect P450c17 enzymatic activity, wild type and mutant CYP17A1 cDNAs were cloned into flag-tagged pcDNA3 vector and introduced into human embryonic kidney cells 293T (HEK293T) cells. Protein expression levels of CYP17A1 were then analyzed. And the activities of 17α-hydroxylase and 17,20-lyase of CYP17A1 were evaluated by measuring the conversion of progesterone to 17α-hydroxyprogesterone and of 17α-hydroxypregnenolone to dehydroepiandrosterone, respectively. In addition a computer model was used to create the three-dimensional structure of the mutant CYP17A1 enzymes. RESULTS: Production of the p.His373Leu mutant protein was significantly lower than that of the wild type protein, and the p.Glu383fsX36 protein was hardly produced. Similarly the enzymatic activity derived from the p.His373Leu mutant vector was significantly lower than that obtained from the wild type vector, and little activity was obtained from the p.Glu383fsX36 vector. Three-dimensional modeling of the enzyme showed that p.His373 was located in region important for heme-binding and proper folding. Neither the p.His373Leu nor the p.Glu383fsX36 mutant protein formed a heme-binding structure. CONCLUSION: Enzyme activity measured in both mutants disappeared completely in both 17α-hydroxylase and 17,20-lyase. This result accounts for the clinical manifestations of the patient with the compound heterozygous CYP17A1 mutations.

Novel Mutation (c.8725T>C) in Two Siblings With Late-Onset LAMA2-Related Muscular Dystrophy

No abstract available.

Novel Mutation (c.8725T>C) in Two Siblings With Late-Onset LAMA2-Related Muscular Dystrophy

No abstract available.

Evaluation of the Automated Immunohematology Analyzer DAYMATE M

BACKGROUND: An automated immunohematology analyzer, DAYMATE M (DAY Medical, Switzerland), has been recently developed. The potential of this analyzer to improve test results has been evaluated. METHODS: A total of 300 blood samples from Seoul St. Mary's hospital and Incheon St. Mary's hospital were tested for ABO and RhD typing. In addition, 336 antibody screening test (AST) samples and 82 patients treated with hematopoietic stem cell transplantation (HSCT) were included. AST results by DAYMATE M were compared with those obtained by a manual method using DS-Screening II (Bio-Rad Laboratories, Switzerland) and red blood cells from Selectogen (Ortho-Clinical diagnostics Inc., USA). RESULTS: Of the 300 patients enrolled, 87, 73, 79, and 61 had type A, B, O, and AB blood, respectively. The concordance rate was 99.9% for cell typing and 97.0% for serum typing. One discordant case was classified as type B instead of AB, and six discordant serum-typing cases were type A, but classified as type AB. Among the 336 AST samples, the concordance rate was 93.2%. From 136 positive cases, six were discordant. Within the 82 HSCT-treated patients, the concordance rate for ABO blood typing was 92.2%. Among the six discordant cases, DAYMATE M typed four cases as donor type where the standard method typed them as the recipient blood type. CONCLUSIONS: The DAYMATE M automated immunohematology analyzer performs reliably for ABO and RhD typing, as well as for ASTs and on samples from patients treated with HSCT.

Sigma-Metrics of Electrolyte Tests From a Recently Launched New-Generation Proficiency Testing Program of the Korean Association of Quality Assurance for Clinical Laboratory

No abstract available.

Survey of Fungal Cultures and the Identification Tests Used by Diagnostic Laboratories in Korea

BACKGROUND: The aim of this study was to investigate the current status of fungal cultures and the identification tests used by diagnostic laboratories in Korea. METHODS: From 22 October to 30 November 2013, we surveyed 76 laboratories, participating in the regular proficiency survey program of The Korean Association of Quality Assurance for Clinical Laboratory, with a questionnaire on fungal cultures and their identification tests. In March 2014, five mold were distributed to ninety-one participating laboratories, as an educational challenge. RESULTS: Fifty-six (73.7%) out of seventy-six laboratories replied to the survey questionnaire. Yeast was identified using commercial kits in all laboratories and to species level in 82.1% of the laboratories, whereas moulds were mainly identified by morphological examinations, to species level in 41.1% of the laboratories. The response rate to the five proficiency specimens was 67.0%–71.1%. The percentage of correctly identified dermatophytes was lower than that of Aspergillus species. CONCLUSIONS: An improvement is required in the mould culturing and identification techniques used in diagnostic laboratories in Korea.

Genetic–pathologic characterization of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders characterized by the proliferation of one or more myeloid lineages. The current study demonstrates that three driver mutations were detected in 82.6% of 407 MPNs with a mutation distribution of JAK2 in 275 (67.6%), CALR in 55 (13.5%) and MPL in 6 (1.5%). The mutations were mutually exclusive in principle except in one patient with both CALR and MPL mutations. The driver mutation directed the pathologic features of MPNs, including lineage hyperplasia, laboratory findings and clinical presentation. JAK2-mutated MPN showed erythroid, granulocytic and/or megakaryocytic hyperplasia whereas CALR- and MPL-mutated MPNs displayed granulocytic and/or megakaryocytic hyperplasia. The lineage hyperplasia was closely associated with a higher mutant allele burden and peripheral cytosis. These findings corroborated that the lineage hyperplasia consisted of clonal proliferation of each hematopoietic lineage acquiring driver mutations. Our study has also demonstrated that bone marrow (BM) fibrosis was associated with disease progression. Patients with overt fibrosis (grade ⩾2) presented an increased mutant allele burden (P<0.001), an increase in chromosomal abnormalities (P<0.001) and a poor prognosis (P<0.001). Moreover, among patients with overt fibrosis, all patients with wild-type JAK2/CALR/MPL (triple-negative) showed genomic alterations by genome-wide microarray study and revealed the poorest overall survival, followed by JAK2-mutated MPNs. The genetic–pathologic characteristics provided the information for understanding disease pathogenesis and the progression of MPNs. The prognostic significance of the driver mutation and BM fibrosis suggests the necessity of a prospective therapeutic strategy to improve the clinical outcome.

Identification of a Heterozygous SPG11 Mutation by Clinical Exome Sequencing in a Patient With Hereditary Spastic Paraplegia: A Case Report

Next-generation sequencing, such as whole-genome sequencing, whole-exome sequencing, and targeted panel sequencing have been applied for diagnosis of many genetic diseases, and are in the process of replacing the traditional methods of genetic analysis. Clinical exome sequencing (CES), which provides not only sequence variation data but also clinical interpretation, aids in reaching a final conclusion with regards to genetic diagnosis. Sequencing of genes with clinical relevance rather than whole exome sequencing might be more suitable for the diagnosis of known hereditary disease with genetic heterogeneity. Here, we present the clinical usefulness of CES for the diagnosis of hereditary spastic paraplegia (HSP). We report a case of patient who was strongly suspected of having HSP based on her clinical manifestations. HSP is one of the diseases with high genetic heterogeneity, the 72 different loci and 59 discovered genes identified so far. Therefore, traditional approach for diagnosis of HSP with genetic analysis is very challenging and time-consuming. CES with TruSight One Sequencing Panel, which enriches about 4,800 genes with clinical relevance, revealed compound heterozygous mutations in SPG11. One workflow and one procedure can provide the results of genetic analysis, and CES with enrichment of clinically relevant genes is a cost-effective and time-saving diagnostic tool for diseases with genetic heterogeneity, including HSP.

Identification of Compound Heterozygous Mutations in the BBS7 Gene in a Korean Family with Bardet-Biedl Syndrome

No abstract available.