BACKGROUND: Anti-double stranded DNA antibody (anti-dsDNA) test is useful for the diagnosis and monitoring of systemic lupus erythematosus (SLE). Although several methods are available, none of them is completely satisfactory and differences among them have been reported. We evaluated the diagnostic performance of 6 commercial kits for anti-dsDNA detection. METHODS: A total of 142 sera (SLE [N=74], other systemic rheumatic diseases [N=50], other diseases [N=18]) were tested by 6 different assay kits using different antigenic sources of DNA: Crithidia luciliae immunofluorescence test (CLIFT), salmon testes (immunoblot, IB), human (ELISA I), salmon testes with nucleosome linker (ELISA II), plasmid (ELISA III), and synthetic oligonucleotides (chemiluminescence immunoassay, CLIA). RESULTS: With manufacturers' cut-off values, 6 test kits showed sensitivities of 55.4-91.9%. ELISA I had a greater sensitivity than the other five assays (P<0.001). The specificities of ELISA II, ELISA III, CLIA, and CLIFT were higher than those of ELISA I and IB (P<0.05). In ROC curve analysis, 3 ELISA kits and CLIA showed AUC values of 0.845-0.893, and revealed no significant differences among them (P>0.05). With cut-off values set at 95% of specificity, ELISA II had a higher sensitivity than ELISA III (63.5% vs. 41.9%, P<0.05). IB had poor concordance rates with other assays (42.0-65.0%). Pearson correlation coefficients among 4 quantitative assays were 0.667-0.798. CONCLUSIONS: Six different assays showed various performances depending on the methods and cut-off values used. Except IB, the other five assays can be used for the detection of anti-dsDNA.
Adult ; Antibodies, Antinuclear/*analysis ; Area Under Curve ; Chemiluminescent Measurements/*methods ; DNA/*immunology ; Enzyme-Linked Immunosorbent Assay/*methods ; Female ; Fluorescent Antibody Technique/*methods ; Humans ; Immunoblotting/*methods ; Lupus Erythematosus, Systemic/diagnosis ; Male ; Middle Aged ; ROC Curve ; Reagent Kits, Diagnostic ; Sensitivity and Specificity

BACKGROUND: Hepatitis C virus (HCV) core antigen (Ag) levels are known to be well correlating with HCV RNA levels, and may be used as an alternative marker of HCV replication for monitoring the response to HCV treatment. However, the low sensitivity of HCV core Ag assay has been an obstacle for clinical use. In this study, recently developed ARCHITECT HCV Ag assay (Abbott Laboratories, USA) was evaluated for analytical performance and clinical usefulness. METHODS: A total of 109 sera from HCV infected patients including various genotypes of HCV (1b, 2, 2a/2c, 2b, and 3a) and 20 sera from healthy donors were used for evaluating the sensitivity, precision, and linearity of the HCV core Ag assay. The cross reactivity with HIV, hepatitis B virus and myeloma proteins (N=5, each) and correlation with HCV RNA PCR assay were also evaluated. RESULTS: The sensitivity of the HCV core Ag assay was 97.2% (106/109) and there were no false positive results and cross reactivity. The within-run, between-run and between-day CVs were 3.0%, 2.5% and 3.0%, respectively. The levels of HCV core antigen showed a good correlation with those of HCV RNA quantification (r=0.940). The HCV Ag assay showed an excellent linearity in the range from 0.63 to 17,114 fmol/L (r=0.999). CONCLUSIONS: The ARCHITECT HCV Ag assay was good in sensitivity, precision, and linearity and its results well correlated with HCV RNA levels. This assay could be used as a good marker of viral replication for monitoring the therapy response in chronically HCV infected patients.
Chemiluminescent Measurements/*methods ; Cross Reactions ; Genotype ; Hepacivirus/genetics/*immunology ; Hepatitis Antigens/*blood ; Humans ; Polymerase Chain Reaction/*methods ; RNA, Viral/blood ; Reagent Kits, Diagnostic ; Sensitivity and Specificity ; Viral Core Proteins/*blood

BACKGROUND: The Lewis histo-blood group system consists of 2 major antigens-Lea and Leb-and a sialyl Lewis antigen-carbohydrate antigen (CA) 19-9. We investigated the distribution of Lewis genotypes and evaluated the relationship between the Lewis/Secretor genotypes and the serum level of CA 19-9 in a Korean population to identify whether the serum CA 19-9 levels are influenced by the Lewis/Secretor genotypes. METHODS: The study included 242 individuals who had no malignancies. Lewis genotyping was performed for the 59T>G, 508G>A and 1067T>A polymorphic sites. The Secretor genotype was determined through analysis of the 357C>T and 385A>T polymorphic sites and the fusion gene. Serum CA 19-9 level was analyzed using an electrochemiluminescence immunoassay. RESULTS: Individuals carrying the 3 common genotypes-Le/Le, Le/le(59,508), and Le/le(59,1067)-accounted for 95% of the study population. In the Korean population, the allelic frequencies of Le, Le(59), le(59,508), and le(59,1067) were 0.731, 0.010, 0.223, and 0.035, respectively. We found a significant difference in serum CA 19-9 concentrations among the 9 Lewis/Secretor genotype groups (P<0.001). The serum CA 19-9 levels in subjects with genotype groups 1 and 2 (Le/- and se/se) were higher than those with genotype groups 3-6 (Le/- and Se/-; 15.63 vs 6.64 kU/L, P<0.001). CONCLUSIONS: Le/Le, Le/le(59,508), and Le/le(59,1067) are frequent Lewis genotypes in Koreans. Because serum CA 19-9 levels are significantly influenced by the Lewis/Secretor genotypes, caution is suggested when interpreting the serum CA 19-9 levels.
Adult ; Aged ; Alleles ; Asian Continental Ancestry Group/*genetics ; CA-19-9 Antigen/*blood ; Chemiluminescent Measurements/methods ; Female ; Gene Frequency ; Genotype ; Humans ; Immunoassay/methods ; Lewis Blood-Group System/*genetics ; Male ; Middle Aged ; Phenotype ; Polymorphism, Genetic ; 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

Autoantibodies against thyroxin (T4AA) and triiodothyronine (T3AA) are present in dogs with autoimmune thyroiditis and have been reported to interfere with immunoassays. The objectives of this study were to determine the frequency of autoantibodies and to determine whether interference occurs by T4AA, using a non-immunological method (high performance liquid chromatography, HPLC) for thyroxin (T4) measurement. Based on clinical symptoms, T4 and thyroid stimulating hormone (TSH) concentration, 1,339 dogs were divided into six groups: Group 1: hypothyroid (n = 149); Group 2: subclinical thyroiditis (n = 110); Group 3: suspicious for non thyroidal illness (n = 691); Group 4: biochemical euthyroid (n = 138); Group 5: hypothyroid dogs under substitution therapy (n = 141); Group 6: healthy dogs (n = 110). The incidence of T4AA and T3AA, determined using radiometric assay, was low (0.5% and 3.8%) and higher in hypothyroid dogs compared to dogs suspicious for hypothyroidism (Group 2-4) (p<0.05). T4AA was not detected in dogs with normal T4 and elevated TSH. T4 concentrations of T4AA positive samples determined using HPLC were comparable to results obtained by chemiluminescence immunoassay. These findings indicate that the probability of interference of T4AA leading to falsely elevated T4 concentration in the T4 assay seems to be low.
Animals ; Autoantibodies/*immunology ; Chemiluminescent Measurements/methods/*veterinary ; Chromatography, High Pressure Liquid/veterinary ; Dog Diseases/*diagnosis/*immunology ; Dogs ; Immunoassay/methods/*veterinary ; Thyroid Hormones/*immunology ; Thyroiditis, Autoimmune/diagnosis/immunology/*veterinary ; Thyroxine/*blood

BACKGROUND: To establish effective preventive measures for hepatitis A virus (HAV) infection, a nationwide epidemiologic study on seroprevalence of anti-HAV and the disease prevalence is needed. The aim of this study was to analyze the recent sero-epidemiological changes of hepatitis A markers in Korea. METHODS: The results of 11,068 anti-HAV total and 32,360 anti-HAV IgM tests by electro-chemiluminescence immunoassay (ECLIA) that had been requested in recent four years (2005-2008) to a reference medical laboratory from 1,699 institutions nationwide were retrospectively analyzed according to the distribution of year, sex, and age groups. RESULTS: The overall positive rate of anti-HAV total was 62.8%. The overall positive rate of anti-HAV IgM was 11.0%, showing a significantly increasing trend by year: 7.7%, 10.9%, 8.9%, and 14.3% in 2005, 2006, 2007, and 2008, respectively (P<0.0001). The positive rate of anti-HAV IgM was higher in male than in female subjects (11.8% vs 10.0%, P<0.0001), and 81.8% (2,916/3,566) of the anti-HAV IgM positive results were observed in the age groups of 21-40 yr. The annual positive rates of anti-HAV total and anti-HAV IgM showed significantly decreasing and increasing trends, respectively, in the age groups of > or =21 yr. Conclusion: In accordance with a decreasing sero-positivity of anti-HAV total, the prevalence of acute hepatitis A virus infection has been considerably increased during the recent four years in the age groups of > or =21 yr. The results of this study could be used effectively as a basic data for establishing effective preventive measures for hepatitis A including vaccination in these susceptible age groups.
Adult ; Biological Markers/blood ; Chemiluminescent Measurements ; Enzyme-Linked Immunosorbent Assay ; Female ; Hepatitis A/*epidemiology ; Hepatitis A Antibodies/*blood ; Hepatitis A virus/*immunology ; Humans ; Immunoglobulin M/blood ; Male ; Middle Aged ; Republic of Korea/epidemiology ; Retrospective Studies ; Sex Factors ; Time Factors

BACKGROUND: Primary human cytomegalovirus (CMV) infection during pregnancy is a major cause of congenital malformation. We detected primary CMV infection in pregnant Korean women by using an algorithm that comprises CMV IgG, IgM, and IgG avidity tests. METHODS: During a 2-month period, 744 pregnant women who were at 10-19 weeks of gestation were consecutively enrolled in this study. Human anti-CMV IgG and IgM levels in their sera were determined by chemiluminescence immunoassays. Serum samples from the women who were positive for CMV IgG and IgM were assayed by the ARCHITECT CMV IgG avidity test in order to distinguish primary from non-primary CMV infection. Gross examination of the neonates of the women who were positive for CMV IgM was conducted. RESULTS: The seroprevalence of CMV IgG and IgM was estimated to be 98.1% and 1.7%, respectively. The samples from all the women who were positive for CMV IgM or with grey zone results contained high avidity CMV IgG. Seven women with positive CMV IgG and IgM results who completed follow-up up to delivery showed no gross evidence of in utero CMV transmission. CONCLUSIONS: Maternal primary CMV infection was not detected in any of the pregnant women included in this study cohort. CMV IgG avidity test enabled the identification of women who were at a low risk of transmitting CMV infection and provided informative for subsequent pregnancy outcomes. Compared to previous studies, the seroprevalence of CMV IgG antibody across pregnant Korean women remained unchanged.
Adult ; Antibodies, Viral/*blood ; Asian Continental Ancestry Group ; Chemiluminescent Measurements ; Cytomegalovirus/*immunology ; Cytomegalovirus Infections/*diagnosis/epidemiology ; Enzyme-Linked Immunosorbent Assay ; Female ; Gestational Age ; Humans ; Immunoglobulin G/*blood ; Immunoglobulin M/blood ; Pregnancy ; Pregnancy Complications, Infectious/*diagnosis/epidemiology ; Republic of Korea ; Seroepidemiologic Studies ; Young Adult

BACKGROUND: Due to the westernization of living environments in Korea, a number of allergy patients are greatly increasing. External quality control assessments are difficult for allergy tests due to the lack of reference methods. We surveyed the current status of allergy tests performed in medical laboratories in Korea to prepare for an external quality control assessment in the near future. METHODS: We conducted a survey on internal and external quality control trials, calibrations and its intervals, medical staffs, analyzers in use, an average number of tests per months, and report formats. RESULTS: Among the 85 laboratories surveyed, 61 were doing allergy tests including 6 reference laboratories. There were two different types of analyzers (1) qualitative or semi-quantitative and (2) quantitative. These analyzers use either chemiluminescent or immunoblot method. Fifty-five laboratories were using 'qualitative or semi-quantitative' analyzers as a screening test and 31 laboratories were using quantitative analyzers. Most of the laboratories were only doing an internal quality control assessment included in the test kits. Excepting a few laboratories, calibrations were not done. About 34 laboratories reported numerical values with interpretative reports prepared by laboratory medical doctors. CONCLUSIONS: The necessity of external quality control assessment has become an issue for improving the quality of allergy tests. But due to the lack of standardization, it is difficult to carry out external quality control assessments. By grouping the laboratories in terms of the type of analyzers, we could overcome the problem of analyzer variations and launch an external quality control assessment program in the near future.
Allergens/*immunology ; Chemiluminescent Measurements/standards ; Humans ; Immunoassay/instrumentation/*standards ; Immunoblotting/standards ; Immunoglobulin E/*blood/immunology ; Korea ; Quality Control

BACKGROUND: An increased level of beta2-microglobulin (beta2M) is seen in diseases such as lymphoproliferative diseases, renal diseases, solid tumors, liver diseases, certain viral infection, or chronic inflammatory diseases, etc. In this study, we evaluated a quantitative beta2M assay for precision and linearity using an automated turbidimetric immunoassay (TIA) by Hitachi 7600-110 (Hitachi High Technologies Co., Japan). The TIA of beta2M was compared with a chemiluminescent immunoassay (CLIA) by Immulite 2000 (Diagnostic Products Corporation, USA). METHODS: Two TIAs, the Hitachi 7600-110 with Roche reagent (Roche-TIA) and the Hitachi 7600- 110 with HBI reagent (HBI-TIA), were evaluated for within-run precision, within-day precision, betweendays precision, and linearity. With 68 serum samples, two TIAs were compared with Immulite 2000 using DPC reagent (DPC-CLIA). These data were analyzed by Passing-Bablok analysis and Bland- Altman analysis. RESULTS: The coefficients of variation (CVs) of within-run precision, within-day precision, and between- days precision were less than 7% in all groups. The linearity tests of the two TIAs were maintained well (Roche-TIA: R2=0.9952; HBI-TIA: R2=0.9946). The comparison study indicated good correlations (Roche-TIA/DPC-CLIA: r=0.9738, y=0.9625x-0.0375; HBI-TIA/DPC-CLIA: r=0.9725, y= 1.1000x-0.3100). In Bland-Altman analysis, less than 2SD differences were observed between the two groups. CONCLUSIONS: Both Roche-TIA and HBI-TIA showed a good precision and excellent correlations with DPC-CLIA; therefore, TIA could be used in the routine laboratory to determine a quantitative analysis of beta2M.
Aged ; Chemiluminescent Measurements ; Enzyme Multiplied Immunoassay Technique ; Female ; Humans ; Immunoassay/*methods ; Male ; Middle Aged ; Nephelometry and Turbidimetry ; Reagent Kits, Diagnostic ; Regression Analysis ; Sensitivity and Specificity ; beta 2-Microglobulin/*analysis

Many allergists are currently focusing on the development of new diagnostic tools, and are attempting to improve both the sensitivity and specificity. A multiple allergen simultaneous test-chemiluminescent assay (MAST-CLA) is one of the most popular diagnostic tools used in the Republic of Korea. However, there remains controversy among allergists with regard to the cut-off point for a positive result. The present study was conducted in order to determine the validity of MAST-CLA as compared with that of the skin prick test, with particular emphasis on arthropod allergens, on the basis of percentage agreement rates and k-values, and also to suggest the optimal positive cutoff points using receiver operating characteristic (ROC) curves. The study was conducted with 97 subjects (54 men, 43 women). Optimal individual cut-off points were calculated as follows; class II for Dermatophagoides farinae, class I for Dermatophagoides pteronyssinus, and trace for a cockroach mix. These findings suggest that attempting to apply optimal individual cut-off points will be a good way of improving diagnostic tests, particularly MAST-CLA.
Adult ; Allergens/*immunology ; Animals ; Antigens, Dermatophagoides/*immunology ; Chemiluminescent Measurements/*methods/standards ; Cockroaches/chemistry ; Dermatophagoides farinae/chemistry ; Dermatophagoides pteronyssinus/chemistry ; Female ; Humans ; Hypersensitivity/*diagnosis/immunology ; Insect Proteins/*immunology ; Male ; *ROC Curve ; Skin Tests/methods