Report on the External Quality Assessment Scheme of Hepatitis Viral Markers in Korea, (2016–2017)

As part of the immunoserology program of the Korean Association of External Quality Assessment Service, we organized two trials on the external quality assessment of hepatitis viral markers in 2016 and 2017. The hepatitis viral antigens and antibodies program consisted of 10 test items. We delivered two and three types of pooled sera specimens to 965 and 965 institutions for the first and second trials of external proficiency testing in 2016, respectively. The number of participating laboratories was 915 (94.8%) and 913 (95.0%) in the first and second trials in 2016, respectively. We also delivered three kinds of pooled sera specimens to 936 and 1,015 institutions for the first and second trials of external proficiency testing in 2017, respectively. The number of participating laboratories was 920 (98.3%) and 996 (98.1%) in the first and second trials in 2017, respectively. The most commonly tested items were hepatitis B surface antigen, followed by the antibodies to hepatitis B surface antigen, anti-hepatitis C virus, hepatitis B envelope antigen, antibodies to hepatitis B envelope antigen, anti-hepatitis A virus and antibodies to hepatitis B core antigen. The most frequently used methods for detecting viral markers were the chemiluminescence immunoassay and the electrochemiluminescence immunoassay, but they yielded a few-false positive results due to the matrix effect. The immunochromatographic assay yielded false-negative results for anti-hepatitis A virus due to low sensitivity. Continuous improvement in the quality of viral hepatitis testing through participation in the survey seems necessary.

Development and Performance Evaluation of External Quality Controls for Allergen-Specific Immunoglobulin E Tests

BACKGROUND: Many companies have developed different methods and products for allergen-specific immunoglobulin E (IgE) tests. Because there is no standardised reference method, external quality assessment (EQA) is important for allergen-specific IgE test to ensure the comparability and reliability of the results from different laboratories. We prepared specimens for EQA of allergen-specific IgE tests and evaluated their stability. METHODS: Four pooled sera with 24 selected allergen-specific IgE levels were prepared and stored at −80℃. The stability of allergen-specific IgE levels was assessed on days 1, 7, and 14 at −20℃, 2℃ to 8℃, and 20℃ to 25℃, and then after 3 months at −80℃. Mock proficiency tests were performed with the four sets of prepared external quality controls for six laboratories, using the commercial multiple allergen simultaneous test (MAST) methodology. RESULTS: About 150 specimens (650 µL each) for EQA were prepared; randomly selected specimens showed similar IgE levels for the 24 allergens (±1 class). The levels of allergen-specific IgE remained stable throughout the study period (P>0.05). Although mock survey results from six laboratories using four MAST assays revealed some variability with a difference (2–3 class), no consistent differences were observed through the allergens or MAST methods. Qualitative results from the mock survey showed 85.4% (cut-off of class 1) and 81.3% (cut-off of class 2) concordance with the results from ImmunoCAP (Phadia, Sweden). CONCLUSIONS: The pooled sera prepared for allergen-specific IgE tests might be adequate and useful for EQA.

Evaluation on the Stability of Pooled Sera for External Quality Assessment of Tumor Marker Assays / 임상검사와정도관리

BACKGROUND: Specimens for the external quality assessment (EQA) need to be highly stable during the EQA process. Therefore, we evaluated the stability of pooled sera (PS) for tumor markers including alpha fetoprotein (AFP), carcinoembryonic antigen (CEA), carbohydrate antigen 125 (CA 125), and carbohydrate antigen 19-9 (CA 19-9). METHODS: PS with 2 different levels (high and low) of each of the 4 tumor markers were collected and stored at -20degrees C, 4degrees C, and room temperature (RT). The concentration of each tumor marker was then measured after storage under these different conditions at baseline and on days 1, 3, 7, 14, 30, 90, and 181. Internal quality control (QC) results during the evaluation period were also analyzed. RESULTS: Irrespective of storage conditions, coefficients of variation (CVs) of AFP and CA 125 levels in the PS during the evaluation period ranged from 3.3% to 7.5% in EQA assays and were similar to the CVs of QC assays. However, the levels of CEA detected in PS stored at -20degrees C, and 4degrees C, showed higher variability, with CVs ranging from 4.0% to 10.4%, and samples stored at RT showed especially high CVs, i.e., >8.3%. Samples for CA 19-9 testing stored at RT also showed lower stability than the QC samples as well as samples stored at -20degrees C, after 3 days. CONCLUSIONS: CEA and CA 19-9 levels in PS showed higher variability than AFP and CA 125, especially when stored at RT. These results indicate that all EQA specimens for tumor marker assays need to be tested as soon as possible and not stored at RT for longer than 3 days during the EQA process.

Comparative Analysis of Immunoreactivity between Individual Serum and Pooled Serum in Serum Screening / 소아알레르기및호흡기학회지

PURPOSE: Serum screening test to detect specific immunoglobulin E (IgE) is an important step for the assessment of potential allergenicity of genetically modified (GM) food. The purpose of this study was to evaluate the usefulness of pooled serum for serum screening instead of individual serum. METHODS: Children with allergic disease were recruited and those who were sensitized to peanut or egg white were selected to obtain their sera. Sensitization to these foods was determined when the level of specific IgE was over 0.35 kU/L by ImmunoCAP. The patients were divided into subgroups according to their level of specific IgE. Raw proteins were extracted and immunoblot analysis was performed to compare the immunoreactivity between individual serum and pooled serum. RESULTS: Pooled serum from peanut-sensitized allergic children showed all the bands which were shown in immunoblot analysis by using individual serum and peanut protein extract. These findings were demonstrated both in pooled serum with low level of peanut-specific IgE and in those with high level of peanut-specific IgE. Likewise, there was no difference in the immunoreactivity between individual serum and pooled serum from egg white-sensitized allergic children. CONCLUSION: Pooled serum can be used as an alternative to individual serum for the serum screening in the allergenicity assessment of GM food.

HBV DNA assay using PCR-microfluidic chips for blood screening / 中国输血杂志

Objective To test HBV DNA by using PCR-microfluidic chip assay. Methods Pooled sera ( 5?50ul ) negative for ELISA serological tests were tested for HBV DNA using PCR-microfluidic chips assay. Individual donor samples were tested if the pooled sera were positive. The sensitivity of PCR-microfluidic chips assay was determined by serial dilutions of the standard control serum. The specificity of PCR-microfludic chips assay was also determined by testing 56 various serum samples. Serial dilutions of the standard control sera were tested repeatedly for understanding the inter- and intra-assay variation of this method. Results Seven of 545 nonrenumerated donors (1.28%) were found positive for HBV DNA. The sensitivity of PCR-microfluidic chips assay was 4.81?102copies/ml. The HBV DNA was positive for all 37 samples from HBeAg positive patients. The HBV DNA tests of samples from HCV RNA positive patients, anti-HAV IgM positive patients were all negative. The inter- and intra assay CV ranges were 15.6%~40.2% and 11.9%~30.6% respectively. Conclusion It is necessary to test HBV DNA for improving blood safety and it is feasible to test pooled serum samples for HBV DNA by PCR-microfluidic chips assay, because it is convenient, time-saving, sensitive, specific and the results are reproducible.