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.

No abstract available.
Immunoassay ; Prostate ; Prostate-Specific Antigen

BACKGROUND: In Korea, the Korean Laboratory Accreditation Program (KLAP) has set minimum standards for verification of clinical test performance. This verification process is time-consuming and labor-intensive when performed manually. We developed a free, statistical software program for KLAP, using the R language (R Foundation for Statistical Computing, Vienna, Austria). METHODS: We used CLSI guidelines for the algorithm. We built graphic user interfaces, including data input, with Embarcadero Delphi EX4 (Embarcadero Technologies, Inc., Texas, USA). The R Base Package and MCR Package for Method Comparison Regression were used to implement statistical and graphical procedures. RESULTS: Our program LaboStats has six modules: parallel test, linearity, method comparison, precision, reference interval, and cutoff. Data can be entered into the field either manually or by copying and pasting from an MS Excel worksheet. Users can print out precise reports. CONCLUSIONS: LaboStats can be useful for evaluating clinical test performance characteristics and preparing documents requested by KLAP.
Accreditation ; Korea ; Mathematical Computing ; Methods ; Texas

No abstract available.
Disinfectants

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.
Bias (Epidemiology) ; Biomarkers, Tumor ; Breast Neoplasms ; Carcinoembryonic Antigen* ; Disease Progression ; Immunoassay* ; Lung ; Statistics as Topic

BACKGROUND: We evaluated the coincidence rate between Vitek MS system (bioMerieux, France) and Vitek 2 in identifying uropathogens directly from urine specimens. METHODS: Urine specimens submitted to our microbiology laboratory between July and September 2013 for Gram staining and bacterial culture were analyzed. Bacterial identification was performed by using the conventional method. Urine specimens showing a single morphotype by Gram staining were processed by culturing and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS). Of 2,370 urine specimens, 251 showed a single morphotype on Gram staining, and among them, 202 were available for MALDI-TOF MS. RESULTS: In these 202 specimens, colony growth was observed in 189 specimens, and 145 specimens had significant growth of single-colony morphotype in culture. One hundred and ten (75.9%) of them had colony counts of > or =10(5) colony-forming units (CFU)/mL and included 71 enteric gram-negative bacteria (GNB), 5 glucose-non-fermenting GNB, 9 gram-positive cocci (GPC), and 25 yeasts. Furthermore, 70 (98.6%), 3 (60.0%), 4 (44.4%), and 5 (20.0%), respectively, of these were correctly identified by Vitek MS. Thirty-one specimens (21.4%; 11 GNB, 7 GPC, 12 yeasts, and 1 gram-positive bacillus) had colony counts of 10(4)-10(5) CFU/mL. Four specimens (2.8%) yielded colony counts of 10(3)-10(4) CFU/mL. CONCLUSIONS: Vitek MS showed high rate of accuracy for the identification of GNB in urine specimens (> or =10(5) CFU/mL). This could become a rapid and accurate diagnostic method for urinary tract infection caused by GNB. However, for the identification of GPC and yeasts, further studies on appropriate pre-treatment are warranted.
Gram-Negative Bacteria ; Gram-Positive Cocci ; Mass Spectrometry* ; Stem Cells ; Urinary Tract Infections ; Urinary Tract* ; Yeasts

BACKGROUND: Measurement of HbA1c levels is widely used to diagnose diabetes mellitus and to evaluate and monitor plasma-glucose concentrations over 6-8 weeks. In this study, we evaluated the diagnostic performance of the newly developed latex immunoturbidimetric method by using Autolab HbA1c. METHODS: We analyzed and compared the diagnostic performance of Autolab HbA1c with that of Toshiba 200FR between April 2009 and July 2009. According to guidelines (EP5-A2, EP6-P, EP9-A2) of the clinical and laboratory standards institute (CLSI), we compared linearity, precision and correlation of Autolab HbA1c with those of G7 (Tosoh Corp., Kyoto, Japan) by using high-performance liquid chromatography (HPLC) method. RESULTS: Data obtained using Autolab HbA1c showed good linearity in mixtures of samples with low (3.1%) and high (15.1%) levels of HbA1c (r2 = 0.9997). In the analysis of within-run precision of the samples with HbA1c levels of 5.1% and 12.1%, the SDs were 0.04 and 0.06 and covariances of these samples were 0.8% and 0.5%, respectively. In the Deming regression model, the regression equation was as follows: Autolab HbA1c = 1.0859xTosoh HPLC-0.6957. CONCLUSIONS: In this study, Autolab HbA1c method showed better performance characteristics than Tosoh G7 did. In reference review, there was no interference of variant hemoglobin. The data acquisition time of Autolab HbA1c was lower than that of Tosoh G7. The advantages of Autolab HbA1c are that it can be used as an autoanlyzer in routine chemical analysis, it does not require pre-analytical treatment, and the samples are automatically treated with distilled water for hemolysis.
Chromatography, High Pressure Liquid ; Chromatography, Liquid ; Diabetes Mellitus ; Hemoglobins ; Hemolysis ; Latex ; Organothiophosphorus Compounds ; Water

BACKGROUND: Recently, quantitative point-of-care testing (POCT) for cardiac markers using colloidal gold particles was developed in Korea. We evaluated the analytical performance of the HUBI-QUANPRO (Humasis, Korea) assay in comparison with two other assays. METHODS: We evaluated the analytical precision and linearity of HUBI-QUANPRO creatine kinase (CK)-MB, cardiac troponin I (cTnI), and B-type natriuretic peptides (BNP). HUBI-QUANPRO assay was compared with ADVIA Centaur (Siemens, Germany) and Triage (Biosite Diagnostics, USA) assays by using 100 blood samples. In addition, we evaluated the interference of hemoglobin on the HUBI-QUANPRO assay. RESULTS: The coefficients of variation of HUBI-QUANPRO CK-MB, cTnI, and BNP were 7.5-9.7%, 12.0-17.4%, and 14.7-15.7%, respectively. The linearity ranges of HUBI-QUANPRO CK-MB, cTnI, and BNP were 4.7-27.8 ng/mL, 0.76-6.51 ng/mL, and 76.2-762.2 ng/mL, respectively. The comparison study showed no significant difference among them. When 0.5% hemolysis occurred, remarkable hemoglobin interference was found in the three markers resulting in underestimation of the concentrations. CONCLUSIONS: HUBI-QUANPRO CK-MB and BNP showed good analytical performances compared with the other two assays. Hemoglobin interference was noted in the HUBI-QUANPRO assay, especially more in BNP. Although the linearity range of cTnI was narrow, its agreement rate with ADVIA Centaur was good, thus the HUBI-QUANPRO assay could be useful as a quantitative POCT for cardiac markers in the emergency department.
Creatine Kinase ; Emergencies ; Gold Colloid ; Hemoglobins ; Hemolysis ; Korea ; Natriuretic Peptides ; Triage ; Troponin I

BACKGROUND: Total IgE levels in allergic patients tend to be higher than those in healthy individuals. We evaluated the usefulness of total IgE levels in predicting positive results of allergen specific IgEs in multiple allergen simultaneous tests. METHODS: A total of 133 patients with allergic symptoms were evaluated. Allergen specific IgEs were detected using 3 different kits: Allergy screen (R-biopharm, Germany), AdvanSure Allergy Screen (LG Life Science, Korea) and Polycheck allergy (Biocheck Co., Germany). Total IgE was measured by turbidoimmunometric assay (LX-2200, Eiken Chemical Co., Japan). The patients were divided into high (> or =170 IU/mL) and low (<170 IU/mL) groups of total IgE level, and the positive rates and number of positive allergen specific IgEs were evaluated in each group. Positive concordance rates among different kits were also evaluated. RESULTS: High total IgE group showed significantly higher positive rates and number of positive allergen specific IgEs in all of the 3 test kits used compared to low total IgE group. Only two of the allergens, Dermatophagoides farinae and Dermatophagoides pteronyssinus had positive concordance rates of > or =50%. Allergen specific IgEs to these two allergens showed good correlation with total IgE (correlation coefficients >0.5). CONCLUSIONS: Total IgE appears to be useful in predicting positive results in allergen specific IgE tests to common allergens. The specific IgEs to D. farinae and D. pteronyssinus showed good correlation with total IgE. However, for other allergens, significant differences were observed among different test kits, and the standardization of allergens in multiple allergen simultaneous tests is needed.
Adolescent ; Adult ; Aged ; Aged, 80 and over ; Allergens/*immunology ; Animals ; Child ; Child, Preschool ; Dermatophagoides farinae/immunology ; Dermatophagoides pteronyssinus/immunology ; Female ; Humans ; Hypersensitivity, Immediate/*diagnosis ; Immunoglobulin E/*blood ; Male ; Middle Aged ; Predictive Value of Tests ; Reagent Kits, Diagnostic ; Republic of Korea

BACKGROUND: Qualitative hepatitis B surface antigen (HBsAg) assay kits are still commonly used in Korea where hepatitis B virus (HBV) infection is endemic. The accurate determination of HBsAg plays a crucial role in the diagnosis and prevention of HBV infection, especially in endemic areas. The aim of this study was to compare the detection sensitivities of 9 qualitative HBsAg assay kits. METHODS: Seven pooled sera with HBsAg concentration ranging from 0.14 IU/mL to 29.96 IU/mL were prepared. The HBsAg concentration of each pooled serum was determined by a quantitative HBsAg assay, Architect HBsAg (Abbott Laboratories, Ireland). The fully automated immunoassay kits included Elecsys HBsAg (Roche Diagnostics, Germany) and Immulite 2000 HBsAg (DPC, USA) and the rapid tests included 5 immunochromatographic assay (ICA) kits and 2 reverse passive hemagglutination assay (RPHA) kits. RESULTS: Elecsys HBsAg (Roche Diagnostics) showed positive result in pooled serum with HBsAg concentration of 0.14 IU/mL, but Immulite 2000 HBsAg (DPC) showed negative result in the same concentration. Although ICA kits showed variable results among different assay kits, all of them showed negative results in pooled sera with HBsAg concentration of < or =1.89 IU/mL. Two RPHA kits showed negative results in pooled sera with HBsAg concentration of < or =7.98 IU/mL. CONCLUSIONS: Although ICAs were more sensitive than RPHAs, they had variable sensitivities for HBsAg and were less sensitive than the automated immunoassay kits. Therefore, ICAs and RPHAs should be used with caution in the screening tests for HBsAg and their sensitivities need to be improved.
Chemiluminescent Measurements ; Electrochemical Techniques ; Enzyme-Linked Immunosorbent Assay ; Genotype ; Hemagglutination Tests ; Hepatitis B/*diagnosis ; Hepatitis B Surface Antigens/*blood ; Humans ; Reagent Kits, Diagnostic