Serum Wisteria floribunda agglutinin-positive human Mac-2 binding protein level predicts recurrence of hepatitis B virus-related hepatocellular carcinoma after curative resection

Background/Aims@#To investigate whether serum Wisteria floribunda agglutinin-positive human Mac-2-binding protein (WFA+-M2BP) can predict the recurrence of hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) after curative resection. @*Methods@#Patients with chronic hepatitis B (CHB) who underwent curative resection for HCC between 2004 and 2015 were eligible for the study. Recurrence was sub-classified as early (2.14 experienced recurrence more frequently than those with a WFA+-M2BP level ≤2.14 (P=0.011 by log-rank test), and had poorer postoperative outcomes than those with a WFA+-M2BP level ≤2.14 in terms of overall recurrence (56.0 vs. 34.5%, P=0.047) and early recurrence (52.0 vs. 20.7%, P=0.001). @*Conclusions@#WFA+-M2BP level is an independent predictive factor of HBV-related HCC recurrence after curative resection. Further studies should investigate incorporation of WFA+-M2BP level into tailored postoperative surveillance strategies for patients with CHB.

Performance Evaluation of a New Automated Chemiluminescent Immunoanalyzer-Based Interferon-Gamma Releasing Assay AdvanSure I3 in Comparison With the QuantiFERON-TB Gold In-Tube Assay

BACKGROUND: The interferon-gamma (IFN-γ) releasing assay (IGRA) is widely used for latent tuberculosis infection (LTBI) diagnosis. We evaluated the analytical performance of a new automated chemiluminescent immunoanalyzer-based IGRA (CLIA-IGRA), AdvanSure I3 (LG Life Sciences, Seoul, Korea) and compared it with that of the QuantiFERON-TB Gold In-Tube (QFT-GIT) assay. METHODS: Repeatability and reproducibility were evaluated at four levels. Detection capability, including limit of blank (LoB), limit of detection (LoD), and limit of quantification (LoQ), was evaluated using IFN-γ standard material (National Institute for Biological Standards and Control code: 87/586). Agreement between the results of two assays was evaluated using 341 blood samples from healthcare workers and patients at a tertiary care hospital. To determine the cut-off value of CLIA-IGRA for diagnosing LTBI, the ROC curve was analyzed. RESULTS: Repeatability and reproducibility were 4.86–7.00% and 6.36–7.88% CV, respectively. LoB, LoD, and LoQ were 0.022, 0.077, and 0.249 IU/mL, respectively. IFN-γ values between CLIA-IGRA and QFT-GIT showed a strong correlation within the analytical measurable range of both assays, especially when the value was low. Qualitative comparison of the two assays yielded a 99.1% overall agreement (kappa coefficient=0.98). A cut-off value of 0.35 IU/mL was appropriate for diagnosing LTBI. CONCLUSIONS: CLIA-IGRA is a reliable assay for LTBI diagnosis, with performance similar to that of QFT-GIT.

Detection of Anti-Extractable Nuclear Antigens in Patients with Systemic Rheumatic Disease via Fluorescence Enzyme Immunoassay and Its Clinical Utility

Clinical Usefulness of ImmuneCheck™ IgG for Rapid Semiquantitation of Total IgG

BACKGROUND: Conventional IgG assays require costly equipment and skilled experts. Semiquantitative measurement of total IgG using point-of-care testing devices may be the solution for these limitations. This study evaluated the reproducibility of the ImmuneCheck™ IgG assay (ProteomeTech Inc., Korea) and the correlation of its results with conventional laboratory IgG results in the serum and whole blood. METHODS: Both the serum and whole blood samples from 120 patients were used. To evaluate the intra-test reproducibility and inter-test correlation, intraclass correlation coefficient (ICC) analysis was used. RESULTS: The concentration of serum total IgG measured by cobas® 6000 (Roche Diagnostics, Switzland) ranged from 690.4 to 2,756.4 mg/dL. The intra-test reproducibility of ImmuneCheck™ IgG was high (Serum ICC=0.724, P < 0.001; Whole blood ICC=0.843, P < 0.001). The inter-test correlation between the ImmuneCheck™ IgG and cobas® 6000 results was very good (Serum ICC=0.805, P < 0.001; Whole blood ICC=0.842, P < 0.001). Because there were no samples with a total IgG level lower than 600 mg/dL, the pre-existing serum samples were diluted and then the linearity tests were conducted. The intra-test reproducibility for the diluted serum samples was almost perfect (ICC=0.995, P < 0.001), and the inter-test correlation between the ImmuneCheck™ IgG and cobas® 6000 results was also strong (ICC=0.992, P < 0.001). CONCLUSIONS: The ImmuneCheck™ IgG assay is reproducible and highly correlated with the conventional IgG assay for the serum and whole blood. It could be applied for the rapid detection of total IgG.

Diagnostic Performance and Comparative Evaluation of the Architect, Liaison, and Platelia Epstein-Barr Virus Antibody Assays

BACKGROUND: Epstein-Barr Virus (EBV) is one of the most prevalent causes of viral infection in humans. EBV infection stage (acute, past, or absent infection) is typically determined using a combination of assays that detect EBV-specific markers, such as IgG and IgM antibodies against the EBV viral capsid antigen (VCA) and IgG antibodies against the EBV nuclear antigen (EBNA). We compared the diagnostic performance and agreement of results between three commercial EBV antibody assays using an EBV performance panel (SeraCare Life Science, Milford, MA, USA) as a reference. METHODS: EBV antibody tests of EBV VCA IgM, VCA IgG, and EBNA IgG antibodies were performed by the Architect (Abbott Diagnostics, Wiesbaden, Germany), Liaison (DiaSorin, Saluggia, Italy), and Platelia (Bio-Rad, Marnes-la-Coquette, France) assays. Agreement between the three assays was evaluated using 279 clinical samples, and EBV DNA and antibody test results were compared. RESULTS: The three EBV antibody assays showed good diagnostic performance with good and excellent agreement with the performance panel (kappa coefficient, >0.6). The overall VCA IgM positivity rate was higher in EBV DNA-positive samples than in EBV DNA-negative samples for all three EBV antibody assays (P=0.02). The three EBV antibody assays exhibited good agreement in results for the clinical samples. CONCLUSIONS: The diagnostic performance of the three EBV antibody assays was acceptable, and they showed comparable agreement in results for the clinical samples.

Combination of Transient Elastography and an Enhanced Liver Fibrosis Test to Assess the Degree of Liver Fibrosis in Patients with Chronic Hepatitis B

BACKGROUND/AIMS: Liver stiffness (LS) was assessed using transient elastography, and the enhanced liver fibrosis (ELF) test was performed to accurately assess fibrotic burden. We validated the LS-ELF algorithm and investigated whether the sequential LS-ELF algorithm performs better than concurrent combination of these analyses in chronic hepatitis B (CHB) patients. METHODS: Between 2009 and 2013, 222 CHB patients who underwent liver biopsy (LB), as well as LS measurement and the ELF test, were enrolled. RESULTS: Advanced fibrosis (≥F3) and cirrhosis (F4) were identified in 141 (63.6%) and 118 (53.2%) patients, respectively. Areas under receiver operating characteristic curve for LS predictions of ≥F3 (0.887 vs 0.703) and F4 (0.853 vs 0.706) were significantly higher than the ELF test (all p < 0.001). Based on the LS-ELF algorithm, 60.4% to 71.6% and 55.7% to 66.3% of patients could have avoided LB to exclude ≥F3 and F4, respectively, whereas 68.0% to 78.7% and 63.5% to 66.1% of patients could have avoided LB to confirm ≥F3 and F4, respectively. When confirmation and exclusion strategies were applied simultaneously, 69.4% to 72.5% and 60.8% to 65.3% of patients could have avoided LB and been diagnosed as ≥F3 and F4, respectively. The proportion of patients who correctly avoided LB for the prediction of ≥F3 (69.4% to 72.5% vs 42.3% to 59.0%) and F4 (60.8% to 65.3% vs 23.9% to 49.5%) based on the sequential LS-ELF algorithm was significantly higher than the concurrent combination (all p < 0.05). CONCLUSIONS: The sequential LS-ELF algorithm conferred a greater probability of avoiding LB in CHB patients to diagnose advanced fibrosis and cirrhosis, and this test performed significantly better than the concurrent combination.

Comparison of the QIAGEN artus HBV QS-RGQ Assay With the Roche COBAS AmpliPrep/COBAS TaqMan HBV Assay for Quantifying Viral DNA in Sera of Chronic Hepatitis B Patients

BACKGROUND: Hepatitis B virus DNA quantification is essential for managing chronic hepatitis B (CHB). We compared the performance of artus HBV QS-RGQ (QIAGEN GmbH, Germany) and CAP/CTM v2.0 HBV assays (Roche Molecular Diagnostics, USA) in CHB patients. METHODS: A comparative evaluation between two assays was performed with 508 clinical serum samples. Precision, linearity, and the limit of detection (LOD) of QS-RGQ assay was evaluated by using the WHO standard 97/750 and clinical samples. RESULTS: Detection rates and viral loads as determined QS-RGQ assay were significantly lower than those from the CAP/CTM v2.0 assay (52.8% vs 60.6%; 3.55±1.77 IU/mL vs 4.18±1.89 IU/mL, P<0.0001). The kappa coefficient between qualitative results was 0.79 (95% confidence interval, 0.74 to 0.85). Bland-Altman plot found a mean difference of (QS-RGQ − CAP/CTM v2.0)=−0.63 log₁₀ IU/mL (95% limit of agreement, −1.48 to 0.22). Repeatability and total imprecision (% CV) of the QS-RGQ assay were 1.0% and 1.1% at 2,000 IU/mL, and 0.7% and 1.4% at 20,000 IU/mL, respectively. Linearity of this assay ranged from 31.6 to 1.0±10⁷ IU/mL, and the LOD was 2.95 IU/mL. CONCLUSIONS: The artus HBV QS-RGQ assay showed good performance but significantly decreased detection rate and viral load compared with CAP/CTM v2.0 assays. This assay recommends using plasma; however, we used stored serum because of the retrospective study design. Usually HBV DNA quantification is performed in plasma or serum, but sample type and clinical relevance of quantitative values should be considered when determining the clinical application of this reagent.

Two Cases of Antibody-Mediated Rejection Following Kidney Transplantation due to HLA-DQB1 Allele-Specific and DQ Alpha Protein-Specific HLA Antibodies

No abstract available.

Evaluation of Real-time PCR Kits for Epstein-Barr Virus DNA Assays

BACKGROUND: Epstein-Barr virus (EBV) is known to be the causative agent of infectious mononucleosis and EBV-related malignancies. In this study, we compared the results of three real-time PCR kits for EBV DNA assays. METHODS: A total of 300 whole blood samples submitted for quantitative EBV PCR between January 2013 and September 2014 at Severance Hospital were included. The samples were tested by using the Artus EBV RG PCR Kit (Qiagen, Germany), AccuPower EBV Quantitative PCR Kit (Bioneer, Korea), and Real-Q EBV Kit (BioSewoom, Korea). Samples with discordant results between the three kits were confirmed by direct sequencing. RESULTS: The result concordance rate and kappa coefficient (K) were 86.3% and 0.69 for Artus-AccuPower, 93.3% and 0.85 for Artus-Real-Q, and 92.3% and 0.83 for AccuPower-Real-Q, respectively. The correlations between the three kits were found to be significant, with a correlation coefficient of r=0.854 for Artus-AccuPower, -0.802 for Artus-Real-Q, and -0.977 for AccuPower-Real-Q, respectively (P<0.0001). If the real-time PCR concordant results of 258 samples and the direct sequencing results of 42 real-time PCR discordant samples were assumed to be true, the sensitivity/specificity values were 0.921/0.976 for Artus, 0.902/0.965 for AccuPower, and 0.967/1.000 for Real-Q. CONCLUSIONS: The three real-time PCR kits showed excellent sensitivities and specificities. All these kits would be acceptable for clinical and therapeutic management of EBV. However, some discordant results between the kits indicate the need for caution in clinical diagnosis and staging. Further implementation of standardized methodology would be needed for EBV DNA assays.

Annual Report on the External Quality Assessment Scheme for Immunoassay Tests in Korea (2015)

Two trials of external quality assessment were performed in 2015, with 13 test items grouped into four test categories. The first trial materials were sent on May 19, 2015 and the second trial was performed on November 9, 2015 with 13 items including tumor markers, thyroid hormones, cardiac marker troponin (troponin T or troponin I), and procalcitonin (PCT) as biomarkers by immunoassay methods. The bone marker, carboxy-terminal collagen crosslinks (CTX) was replaced by procalcitonin since 2014, because a limited number of institutions performed assays with CTX. External quality surveys of 13 immunoassay test items with 16 control materials were conducted, as scheduled. In total, 13 control materials were used, which consisted of six tumor markers, namely alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), carcinoma antigen (CA) 125, carbohydrate antigen (CA) 19-9, human chorionic gonadotrophin (HCG), and prostate specific antigen (PSA). In addition to tumor markers, 5 thyroid markers, namely thyroid hormone (T)3, T4, thyroid stimulating hormone (TSH), free T4, and thyroglobulin (TG) were included. Furthermore, troponin, as a cardiac marker, and procalcitonin, as a new biomarker, have been adopted since 2014. Five home-made pooled sera and 3 commercial control sera were used as survey materials. MAS Tri-point Liquimmune level 3 (Medical Analysis Systems Inc., USA) was used for thyroid hormones. Procalcitonin and troponin control materials were from Elecsys Precis Control Varia and Elecsys Precis Control Troponin (Roche, Germany), respectively. The number of laboratories participating in the external quality assessment for Immunoassay Subcommittee was 719 institutions in the first trial survey (response rate 98.7%) and 730 institutions in the second survey (94.9%). The test items most frequently used in immunoassays were TSH (93.2%, 93.1%), free T4 (90.3%, 90.2%), and AFP (89.4%, 89.0%), whereas recently adopted biomarkers were less frequently used: troponin I (36.6%, 37.1%), procalcitonin (24.1%, 26.7%), and thyroglobulin (10.3%, 10.7%). The quality of the laboratories participating in the survey seems to be continuously improving, according to their peer group results.

Clinical Utility of a New Automated Hepatitis C Virus Core Antigen Assay for Prediction of Treatment Response in Patients with Chronic Hepatitis C

Hepatitis C virus core antigen (HCV Ag) is a recently developed marker of hepatitis C virus (HCV) infection. We investigated the clinical utility of the new HCV Ag assay for prediction of treatment response in HCV infection. We analyzed serum from 92 patients with HCV infection who had been treated with pegylated interferon and ribavirin. HCV Ag levels were determined at baseline in all enrolled patients and at week 4 in 15 patients. Baseline HCV Ag levels showed good correlations with HCV RNA (r = 0.79, P < 0.001). Mean HCV Ag levels at baseline were significantly lower in patients with a sustained virologic response (SVR) than in those with a non SVR (relapse plus non responder) based on HCV RNA analysis (2.8 log10fmol/L vs. 3.27 log10fmol/L, P = 0.023). Monitoring of the viral kinetics by determination of HCV RNA and HCV Ag levels resulted in similarly shaped curves. Patients with undetectable HCV Ag levels at week 4 had a 92.3% probability of achieving SVR based on HCV RNA assay results. The HCV Ag assay may be used as a supplement for predicting treatment response in HCV infection, but not as an alternative to the HCV RNA assay.

Bone Marrow Chimerism Detection Using Next Generation Sequencing Based on Single Nucleotide Polymorphisms Following Liver Transplantation: Comparison With Short Tandem Repeat-PCR

No abstract available.

Annual Report on External Quality Assessment Scheme for Immunoassay Tests in Korea (2014)

In 2014, two external quality assessment trials were performed on 13 test items grouped in four categories. The laboratories procured the materials for the first and second trials on 13 May 2014 and 11 November 2014, respectively. The trials were performed on 13 test items, including tumour markers, thyroid hormones, cardiac marker troponin (troponin T or troponin I), and procalcitonin as a new biomarker for immunoassay methods. The bone marker carboxy-terminal collagen crosslinks (CTX) has been replaced by procalcitonin this year because only a limited number of institutions used it. External quality surveys of the 13 immunoassay test items with 8 control materials were performed as scheduled. The 13 control materials included six tumour markers, alpha-fetoprotein, carcinoembryonic antigen, carcinoma antigen 125, carbohydrate antigen 19-9, human chorionic gonadotrophin, and prostate specific antigen, as well as five thyroid markers, thyroid hormone 3 (T3), T4, thyroid stimulating hormone, free T4, and thyroglobulin. This year, procalcitonin has been introduced as a new biomarker in addition to troponin, which was introduced last year. Five homemade pooled sera and three commercial control sera were used as survey materials. The MAS Tri-point Liquimmune level 3 (Medical Analysis Systems Inc., USA) was used for controls of thyroid hormones, while Elecsys PreciControl Varia and Elecsys PreciControl Troponin (Roche, Germany) were used for controls of the new biomarkers procalcitonin and troponin, respectively. In the external quality assessment by the Immunoassay Subcommittee, 712 institutions participated in the first trial survey (response rate 97.9%), while 715 participated in the second survey (response rate 97.9%). The quality of the participating laboratories seems to be continuously improving compared to the results of their peers. Additionally, this year procalcitonin has been introduced as a new biomarker instead of the CTX, which was used in 2013, while thyroglobulin and troponin-T/troponin-I, which were used for the 2013 samples, continue to be used in surveys by the Immunoassay Subcommittee.

Interlaboratory Comparison of the Results of Lifecodes LSA Class I and Class II Single Antigen Kits for Human Leukocyte Antigen Antibody Detection

BACKGROUND: Although single antigen bead assays (SAB) are approved qualitative tests, the median fluorescence intensity (MFI) values obtained from SAB are frequently used in combination with quantitative significances for diagnostic purposes. To gauge the reproducibility of SAB results, we assessed the interlaboratory variability of MFI values using identical kits with reagents from the same lot and the manufacturer's protocol. METHODS: Six serum samples containing HLA-specific antibodies were analyzed at five laboratories by using Lifecodes LSA Class I and Class II SAB kits (Immucor, USA) from the same lot, according to the manufacturer's protocol. We analyzed the concordance of qualitative results according to distinct MFI cutoffs (1,000, 3,000, 5,000, and 10,000), and the correlation of quantitative MFI values obtained by the participating laboratories. The CV for MFI values were analyzed and grouped by mean MFI values from the five laboratories ( or =10,000). RESULTS: The categorical results obtained from the five laboratories exhibited concordance rates of 96.0% and 97.2% for detection of HLA class I and class II antibodies, respectively. The Pearson correlation coefficients for MFI values of class I and class II antibodies were between 0.947-0.991 and 0.992-0.997, respectively. The median CVs for the MFI values among five laboratories in the lower MFI range (<1,000) were significantly higher than those for the other MFI ranges (all P<0.01). CONCLUSIONS: Analysis of SAB performed in five laboratories using identical protocols and reagents from the same lot resulted in high levels of concordance and strong correlation of results.

Serum Dickkopf-1 as a Biomarker for the Diagnosis of Hepatocellular Carcinoma

PURPOSE: Dickkopf-1 (DKK-1) is a Wnt/beta-catenin signaling pathway inhibitor. We investigated whether DKK-1 is related to progression in hepatocellular carcinoma (HCC) cells and HCC patients. MATERIALS AND METHODS: In vitro reverse-transcription polymerase chain reaction (RT-PCR), wound healing assays, invasion assays, and ELISAs of patient serum samples were employed. The diagnostic accuracy of the serum DKK-1 ELISA was assessed using receiver operating characteristic (ROC) curves and area under ROC (AUC) analyses. RESULTS: RT-PCR showed high DKK-1 expression in Hep3B and low in 293 cells. Similarly, the secreted DKK-1 concentration in the culture media was high in Hep3B and low in 293 cells. Wound healing and invasion assays using 293, Huh7, and Hep3B cells showed that DKK-1 overexpression promoted cell migration and invasion, whereas DKK-1 knock-down inhibited them. When serum DKK-1 levels were assessed in 370 participants (217 with HCC and 153 without), it was significantly higher in HCC patients than in control groups (median 1.48 ng/mL vs. 0.90 ng/mL, p0.05). When three biomarkers were combined (DKK-1 plus AFP plus DCP), they showed significantly higher AUC (AUC=0.952) than single marker, DKK-1 plus AFP, or DKK-1 plus DCP (all p<0.001). CONCLUSION: DKK-1 might be a key regulator in HCC progression and a potential therapeutic target in HCC. Serum DKK-1 could complement the diagnostic accuracy of AFP and DCP.

Evaluation of Automated Assays for Measuring Serum Hyaluronic Acid: For the Diagnosis of Rheumatoid Arthritis

BACKGROUND: Hyaluronic acid (HA) is present in the connective tissues wherein it functions as a lubricant. HA is known to be increased in both synovial fluid and serum when inflammation occurs in the joint. We measured serum HA concentrations by automated assays and determined its reference interval and its usefulness as a diagnostic marker in patients with rheumatoid arthritis (RA). METHODS: Serum specimens collected from 121 healthy individuals and 253 patients with various arthritis were used for measuring HA with two automated assays, namely, LPIAACE (Mitsubishi, Japan) and LT Auto Wako (Wako, Japan). The association between serum HA concentration and the diagnosis of RA was estimated by receiver operator characteristic (ROC) analysis and multivariate logistic regression. RESULTS: The 95th percentile upper reference limit of serum HA was 57.28 ng/mL (90% confidence interval [CI], 46.30-68.20 ng/mL) for LPIAACE and 72.64 ng/mL (90%% CI, 57.30-85.70 ng/mL) for LT Auto Wako. Area under the ROC curve values of serum HA for discriminating the RA group from the non-RA group were 0.68 for LPIAACE and 0.70 for LT Auto Wako. The odds ratio for serum HA in predicting RA was 1.02 (95% CI, 1.02-1.04) for LPIAACE and 1.03 (95% CI, 1.02-1.05) for LT Auto Wako. CONCLUSIONS: This study provides a reference interval for serum HA concentrations in Koreans. This result suggests that the serum HA concentrations could be helpful as a complementary marker for discriminating RA from other types of arthritis, as well as distinguishing patients with RA from healthy controls.

Resolution of Ambiguous HLA Genotyping in Korean by Multi-Group-Specific Sequence-Based Typing

PURPOSE: To evaluate a multi-group-specific sequence-based typing (SBT) method for resolving ambiguous results from human leukocyte antigen (HLA) genotyping. MATERIALS AND METHODS: A total of 50 samples that showed ambiguous genotypes for at least two HLA loci from HLA-A, -B, -C and -DRB1 by the conventional SBT assay were evaluated using a new SBT test, the AVITA plus assay. The most likely HLA genotypes for the respective samples considering allele frequencies in Korean were concordant between the AVITA and conventional SBT assays. RESULTS: An average of 3.3 loci among the HLA-A, -B, -C and -DRB1 loci per sample gave results with two or more possible allele combinations with the conventional SBT, and 48 (96.0%) out of 50 showed reduced numbers of possible genotypes for at least one HLA locus with the AVITA. A total of 41, 43, 42, and 38 cases among the 50 samples showed ambiguous results for HLA-A, -B, -C, and -DRB1 typing by the conventional SBT, respectively. The average numbers of possible allele combinations for the respective four HLA loci were 8.2, 6.7, 5.9, and 3.2, and they were reduced to 1.5, 2.2, 4.4, and 1.8, respectively, by the AVITA. Ambiguity was resolved by the AVITA in 33 (80.5%), 31 (72.1%), 17 (40.5%) and 28 (73.7%) samples among the ambiguous cases from the conventional SBT for HLA-A, -B, -C, and -DRB1 typing, respectively. CONCLUSION: The multi-group-specific SBT method considerably reduced the number of ambiguous results, and thus may be useful for accurate HLA typing in clinical laboratories.

Annual Report on External Quality Assessment of Immunoassay Testing in Korea (2013) / 임상검사와정도관리

Two external quality assessment trials were conducted on 13 test proteins spanning 4 test categories, in 2013. The first trial was initiated on May 6, 2013, and the second trial of immunoassay tests was conducted on November 12, 2013. The trials analysed tumour markers, thyroid hormones, bone marker carboxy-terminal collagen crosslinks (CTX), and the cardiac marker troponin (troponin T [Tn-T] or troponin I [Tn-I]) used in standard immunoassay testing. Three new markers, i.e., thyroglobulin, CTX, and Tn-T/Tn-I were introduced in 2013 to replace 5 existing marker immunoproteins (immunoglobulin G, immunoglobulin M, immunoglobulin A, complement (C)3, and C4). External quality surveys of 13 immunoassay test items were conducted with the aid of 8 control materials. The tested markers included 6 tumour markers (alpha-fetoprotein, carcinoembryonic antigen, carcinoma antigen 125, carbohydrate antigen 19-9), human chorionic gonadotrophin, and prostate specific antigen), 5 thyroid markers (thyroid hormone 3 [T3], T4, thyroid stimulating hormone, free T4, and thyroglobulin), and 1 bone resorption marker CTX. The newly adopted cardiac marker troponin was also included in this study. Five homemade pooled sera and 3 commercial sera were used as the control sera. The thyroid hormones, novel bone marker CTX, and troponin controls were analysed using the MAS Tri-point Liquimmune level 3 (Medical Analysis System, Inc., USA), Elecsys PreciControl Varia, and Elecsys PreciControl Troponin (Roche, Germany), respectively. The external quality assessment was analyzed by the Immunoassay Subcommittee in 685 institutions in the first trial survey (response rate 97.9%) and 678 institutions in the second survey (95.9%). A consistent improvement was observed in the quality of the participating laboratories, particularly in the peer group results. In addition, three new immunoassay markers, thyroglobulin, CTX, and Tn-T/Tn-I, were introduced to the standard assay systems by the Immunoassay Subcommittee.

Increasing the Efficiency of Laboratory Performance by Using the Onboard Dilution Algorithm of the Elecsys Hepatitis B Surface Antigen II Quantitative Assay / 임상검사와정도관리

BACKGROUND: The Elecsys hepatitis B surface antigen (HBsAg) II quantitative assay is a newly introduced electrochemiluminescence immunoassay incorporating an initial 1:400 onboard dilution and a simple algorithm to determine HBsAg levels in serum. We evaluated the performance of the Elecsys HBsAg II assay and determined the impact of its initial onboard dilution on laboratory efficiency. METHODS: HBsAg levels were determined using both Roche Elecsys and Abbott Architect HBsAg assays. Linearity and precision of the Elecsys HBsAg II assay and its correlation with the Architect HBsAg assay were evaluated. In particular, precision was verified at Samsung Medical Center, Severance Hospital, Seoul St. Mary's Hospital in Seoul, using the same pooled serum controls. The efficiency of the dilution algorithm for both methods was verified using data from 1,848 clinical samples. RESULTS: The Elecsys HBsAg II assay showed a good linearity from 0.1 to 48,000.0 IU/mL and a good correlation (r=0.9998) between expected and measured values. Precision analyses performed at Samsung Medical Center, Severance Hospital, Seoul St. Mary's Hospital showed excellent performance with coefficients of variation between 1.28% and 6.82%. The values of the Elecsys HBsAg II and Architect HBsAg assays were well correlated (n=506, r=0.987, P<0.001) and also reliably determined in hepatitis C virus- and hepatitis B virus-co-infected patient sera (n=27). In terms of efficiency, 64.0% of samples provided a final HBsAg result on the first run without the need for further dilution, when using the 1:400 onboard pre-dilution protocol of the Elecsys HBsAg II assay. CONCLUSIONS: Given the excellent precision and correlation with the Architect assay, the Elecsys HBsAg II assay showed a potential advantage for laboratory efficiency by significantly reducing the need for retesting samples with high HBsAg levels.

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.