Quantitative Evaluation of the Real-World Harmonization Status of Laboratory Test Items Using External Quality Assessment Data.

Background: In recent decades, the analytical quality of clinical laboratory results has substantially increased because of collaborative efforts. To effectively utilize laboratory results in applications, such as machine learning through big data, understanding the level of harmonization for each test would be beneficial. We aimed to develop a quantitative harmonization index that reflects the harmonization status of real-world laboratory tests. Methods: We collected 2021-2022 external quality assessment (EQA) results for eight tests (HbA1c, creatinine, total cholesterol, HDL-cholesterol, triglyceride, alpha-fetoprotein [AFP], carcinoembryonic antigen [CEA], and prostate-specific antigen [PSA]). This EQA was conducted by the Korean Association of External Quality Assessment Service, using commutable materials. The total analytical error of each test was determined according to the bias% and CV% within peer groups. The values were divided by the total allowable error from biological variation (minimum, desirable, and optimal) to establish a real-world harmonization index (RWHI) at each level (minimum, desirable, and optimal). Good harmonization was arbitrarily defined as an RWHI value ≤ 1 for the three levels. Results: Total cholesterol, triglyceride, and CEA had an optimal RWHI of ≤ 1, indicating an optimal harmonization level. Tests with a desirable harmonization level included HDL-cholesterol, AFP, and PSA. Creatinine had a minimum harmonization level, and HbA1c did not reach the minimum harmonization level. Conclusions: We developed a quantitative RWHI using regional EQA data. This index may help reflect the actual harmonization level of laboratory tests in the field.

Impact of Academia-Government Collaboration on Laboratory Medicine Standardization in South Korea: analysis of eight years creatinine proficiency testing experience.

OBJECTIVES: To evaluate the performance of the Academia-Government Collaboration for Laboratory Medicine Standardization in Korea (KR-STDZN) based on data from KR-STDZN proficiency testing (KR-STDZN-PT) for creatinine over eight years (2015-2022). METHODS: We used KR-STDZN-PT data of creatinine tests from 2015 to 2022. Acceptance of the participating institutions' test results was assessed by calculating the acceptance performance as absolute bias (absBias%), total coefficient of variance (tCV%), and total error (TE%) for each sample using six measurements from each institution and true values of each reference material. The test result was considered acceptable when absBias%, tCV%, and TE% were <5.10, <3.20, and <11.40 %, respectively. The proportion of acceptable institutions among all participating institutions in each round was defined as the acceptance rate. Improvements in absBias%, tCV%, and TE% were analyzed using creatinine concentration ranges in samples. RESULTS: The number of participating institutions increased from 2015 to 2017 but remained consistent since 2018. The acceptance rates for absBias% and TE% increased from 52.2 and 77.6 %, in 2015 and to 90.7 and 96.3 %, in 2022, respectively. The acceptance rate for tCV% remained in the 90 % range for eight years. When creatinine <3 mg/dL, mean absBias%, and mean TE% improved significantly in 2021-2022 compared to 2015-2016 (p<0.05). When creatinine >3 mg/dL, acceptance performance did not improve. Mean tCV% remained consistent annually regardless of creatinine concentration. No significant variations in test methods were observed. CONCLUSIONS: The collaboration between academia and the government improved creatinine testing quality. Nevertheless, KR-STDZN must be expanded and refined.

Interpreting changes in consecutive laboratory results: clinician's perspectives on clinically significant change.

BACKGROUND: Clinical laboratory tests are inevitably affected by various factors. Therefore, when comparing consecutive test results, it is crucial to consider the inherent uncertainty of the test. Clinical laboratories use reference change value (RCV) to determine a significant change between 2 results. Whereas the criteria for the interpretation of consecutive results by clinicians are not well known. We investigated the clinician's interpretation of a clinically significant change in consecutive laboratory test results and compared them to RCV. METHODS: We performed a questionnaire survey on clinicians, which comprised 2 scenarios with 22 laboratory test items suggesting initial test results. Clinicians were asked to choose a result showing clinically significant change. RCV of the analytes from EFLM database were collected. RESULTS: We received 290 valid questionnaire responses. Clinicians' opinions on clinically significant change was inconsistent between clinicians and scenarios, and was generally larger than RCV. Clinicians commented that they were not familiar with the variability of the laboratory tests. CONCLUSIONS: Clinicians' opinions on clinically significant changes were more prominent than RCV. Meanwhile, they tended to neglect the analytical and biological variation. Laboratories should properly guide clinicians on the RCV of tests for better decision-making on patients' clinical states.

Evaluation of Vancomycin Area Under the Concentration-Time Curve Predictive Performance Using Bayesian Modeling Software With and Without Peak Concentration: An Academic Hospital Experience for Adult Patients Without Renal Impairment.

Background: The revised U.S. consensus guidelines on vancomycin therapeutic drug monitoring (TDM) recommend obtaining trough and peak samples to estimate the area under the concentration-time curve (AUC) using the Bayesian approach; however, the benefit of such two-point measurements has not been demonstrated in a clinical setting. We evaluated Bayesian predictive performance with and without peak concentration data using clinical TDM data. Methods: We retrospectively analyzed 54 adult patients without renal impairment who had two serial peak and trough concentration measurements in a ≤1-week interval. The concentration and AUC values were estimated and predicted using Bayesian software (MwPharm++; Mediware, Prague, Czech Republic). The median prediction error (MDPE) for bias and median absolute prediction error (MDAPE) for imprecision were calculated based on the estimated AUC and measured trough concentration. Results: AUC predictions using the trough concentration had an MDPE of -1.6% and an MDAPE of 12.4%, whereas those using both peak and trough concentrations had an MDPE of -6.2% and an MDAPE of 16.9%. Trough concentration predictions using the trough concentration had an MDPE of -8.7% and an MDAPE of 18.0%, whereas those using peak and trough concentrations had an MDPE of -13.2% and an MDAPE of 21.0%. Conclusions: The usefulness of the peak concentration for predicting the AUC on the next occasion by Bayesian modeling was not demonstrated; therefore, the practical value of peak sampling for AUC-guided dosing can be questioned. As this study was conducted in a specific setting and generalization is limited, results should be interpreted cautiously.

A New Strategy for Evaluating the Quality of Laboratory Results for Big Data Research: Using External Quality Assessment Survey Data (2010-2020).

Background: To ensure valid results of big data research in the medical field, the input laboratory results need to be of high quality. We aimed to establish a strategy for evaluating the quality of laboratory results suitable for big data research. Methods: We used Korean Association of External Quality Assessment Service (KEQAS) data to retrospectively review multicenter data. Seven measurands were analyzed using commutable materials: HbA1c, creatinine (Cr), total cholesterol (TC), triglyceride (TG), alpha-fetoprotein (AFP), prostate-specific antigen (PSA), and cardiac troponin I (cTnI). These were classified into three groups based on their standardization or harmonization status. HbA1c, Cr, TC, TG, and AFP were analyzed with respect to peer group values. PSA and cTnI were analyzed in separate peer groups according to the calibrator type and manufacturer, respectively. The acceptance rate and absolute percentage bias at the medical decision level were calculated based on biological variation criteria. Results: The acceptance rate (22.5%-100%) varied greatly among the test items, and the mean percentage biases were 0.6%-5.6%, 1.0%-9.6%, and 1.6%-11.3% for all items that satisfied optimum, desirable, and minimum criteria, respectively. Conclusions: The acceptance rate of participants and their external quality assessment (EQA) results exhibited statistically significant differences according to the quality grade for each criterion. Even when they passed the EQA standards, the test results did not guarantee the quality requirements for big data. We suggest that the KEQAS classification can serve as a guide for building big data.

Clinical Relevance of a Vancomycin 24 h Area under the Concentration-Time Curve Values Using Different Renal Function Equations in Bayesian Dosing Software.

With the updated 2020 vancomycin therapeutic drug monitoring (TDM) guidelines suggesting a ratio of area under the curve over 24 h to a minimum inhibitory concentration (AUC24/MIC) as a target from the Infectious Diseases Society of America, an accurate estimation of AUC24 has become more critical. We aim to compare the AUC24 using Bayesian dosing software according to various estimated glomerular filtration rate (eGFR) equations in order to analyze the clinical impact of eGFR in vancomycin TDM. We reviewed the TDM dataset of 214 adult patients and analyzed the AUC24 values from various renal function equations, including the Cockcroft-Gault (C-G), the modification of diet in renal disease (MDRD), the chronic kidney disease epidemiology collaboration (CKD-EPI), and the revised Lund−Malmö. The AUC24/MIC results (assuming a MIC of 1 mg/L) were divided into three groups as follows: <400, 400−600, and >600. Additionally, we compared the group agreement between the C-G and the three eGFR formulas. Although there was a statistically significant difference in the AUC24 of the MDRD and the CKD-EPI formulas compared to the C-G, the group concordance rate of the eGFR formula was 95.2−100%, which indicates no clinical significance. The clinical impact of the eGFR formula type on drug dosing recommendations in vancomycin TDM using Bayesian software was insignificant in clinical practice.

Accuracy of the New Creatinine-based Equations for Estimating Glomerular Filtration Rate in Koreans.

Background: New creatinine-based estimated glomerular filtration rate (eGFR) equations, including the 2021 Chronic Kidney Disease Epidemiology Collaboration (2021 CKD-EPI) and European Kidney Function Consortium (EKFC) equations, have been introduced recently. We assessed the performance of the 2021 CKD-EPI and EKFC equations in the Korean population. Methods: We analyzed 1,654 Korean patients aged ≥18 years who underwent chromium-51-ethylenediamine tetraacetic acid GFR measurements (mGFR). Bias (eGFR-mGFR), root mean square error (RMSE), and proportion of eGFR within 30% of mGFR (P30) of the 2009 CKD-EPI, 2021 CKD-EPI, and EFKC equations were compared. The concordance rate between eGFR and mGFR categories was evaluated. Both eGFR and mGFR categories were classified into six groups: ≥90, 89-60, 59-45, 44-30, 29-15, and <15 mL/min/1.73 m2. Results: The median bias (mL/min/1.73 m2) was 1.8 for the 2009 CKD-EPI equation, 4.8 for the 2021 CKD-EPI equation, and -0.3 for the EKFC equation. The P30 and RMSE were 78.2% and 17.0 for the 2009 CKD-EPI equation, 75.6% and 17.4 for the 2021 CKD-EPI equation, and 80.0% and 16.7 for the EKFC equation, respectively. The overall GFR category concordance rate between eGFR and mGFR was 63.4% for the 2009 CKD-EPI equation, 60.5% for the 2021 CKD-EPI equation, and 61.0% for the EKFC equation. Conclusions: Among the three eGFR equations, the EKFC equation had the smallest bias and highest P30 in Koreans. The 2009 CKD-EPI equation had a lower bias than the 2021 CKD-EPI equation.

Performance of the New RAPIDPoint 500e Blood Gas Analyzer and its Comparison with Central Laboratory Biochemistry Analyzer.

BACKGROUND: Blood gas analyzers are commonly used in point of care settings in hospitals to assess and monitor critically ill patients. The blood gas analyzer, RAPIDPoint 500e (Siemens Healthcare, UK), has been newly introduced. Here, we evaluated the performance of RAPIDPoint 500e for the determination of pH, partial carbon dioxide pressure, partial oxygen pressure, sodium (Na+), potassium (K+), chloride (Cl-), ionized calcium, glucose, and lactate. METHODS: Repeatability, within-laboratory imprecision, and linearity were assessed according to CLSI guidelines. RAPIDPoint 500e results were compared to its previous version RAPIDPoint 500. For Na+, K+, and Cl-, RAPID¬Point 500e results were also compared to the central chemistry analyzer AU5822 (Beckman Coulter, Brea, CA, USA). RESULTS: The coefficients of variation of within-laboratory imprecision for all analytes were less than 5%, within the range of acceptable criteria. The linearity values for all analytes were confirmed within manufacturer claimed range. RAPIDPoint 500e correlated well with both RAPIDPoint 500 and AU5822. Correlation coefficients were over 0.95 for all analytes. CONCLUSIONS: The analytical performance of RAPIDPoint 500e was clinically acceptable.

Comparison between polynomial regression and weighted least squares regression analysis for verification of analytical measurement range.

OBJECTIVES: Recently, the linearity evaluation protocol by the Clinical & Laboratory Standards Institute (CLSI) has been revised from EP6-A to EP6-ED2, with the statistical method of interpreting linearity evaluation data being changed from polynomial regression to weighted least squares linear regression (WLS). We analyzed and compared the analytical measurement range (AMR) verification results according to the present and prior linearity evaluation guidelines. METHODS: The verification of AMR of clinical chemistry tests was performed using five samples with two replicates in three different laboratories. After analyzing the same evaluation data in each laboratory by the polynomial regression analysis and WLS methods, results were compared to determine whether linearity was verified across the five sample concentrations. In addition, whether the 90% confidence interval of deviation from linearity by WLS was included in the allowable deviation from linearity (ADL) was compared. RESULTS: A linearity of 42.3-56.8% of the chemistry items was verified by polynomial regression analysis in three laboratories. For analysis of the same data by WLS, a linearity of 63.5-78.3% of the test items was verified where the deviation from linearity of all five samples was within the ADL criteria, and the cases where the 90% confidence interval of all deviation from linearity overlapped the ADL was 78.8-91.3%. CONCLUSIONS: Interpreting AMR verification data by the WLS method according to the newly revised CLSI document EP6-ED2 could reduce laboratory workload, enabling efficient laboratory practice.

Evaluation of Serum Beta-2-Microglobulin Assay on Beckman Coulter Chemistry Analyzer.

BACKGROUND: Beta-2 microglobulin (ß2M) has various clinical usages and is an important prognostic marker for multiple myeloma. Although there are concerns of harmonization between assays, performance evaluation and method comparison reports are rare. Here, we evaluated the performance of Beckman-Coulter ß2M assay. METHODS: The precision and linearity of the Beckman Coulter ß2M assay were evaluated. Beckman-Coulter results were compared to DiaSorin Liaison results. The manufacturer provided reference interval was verified. RESULTS: Within-laboratory imprecision percentage coefficient of variation was 1.73% and 2.19% for low- and high-level control material, respectively. The linearity was confirmed over a range of 0.08 to 15.60 mg/L. Passing-Bablok regression analysis showed that y (Beckman-Coulter) = 0.978 x (Liaison) + 0.079 (r = 0.996) with a mean difference of 1.0%. All healthy subjects were within the range of manufacturer provided reference interval. CONCLUSIONS: The analytical performance of the Beckman-Coulter ß2M assay was clinically acceptable.

Serum biomarkers for bisphosphonate-related osteonecrosis of the jaw: a prospective clinical study.

In this prospective study, serum levels of 12 possible biomarkers were compared between osteonecrosis of the jaw (ONJ) and control groups, before and after dentoalveolar surgery. The results suggest that patients with abnormal serum levels of specific biomarkers should be monitored closely for the prevention and early diagnosis of ONJ. INTRODUCTION: Bisphosphonate-related osteonecrosis of the jaw (ONJ) is an adverse effect of long-term bisphosphonate therapy. This study aimed to identify bone biomarkers for ONJ risk assessment and diagnosis. METHODS: This prospective study included patients with histories of bisphosphonate therapy without current ONJ who were in need of dentoalveolar surgery of the jaw area. Serum levels of 12 possible bone markers, selected based on their involvement in ONJ pathogenesis, were compared between ONJ and control groups before dentoalveolar surgery (T0), at 8 postoperative weeks (T1), and at 4 months after diagnosis(T2). RESULTS: Seventy-six patients who met the inclusion criteria were included in the study; 33 were assigned to the ONJ group, and 43 patients without ONJ signs or symptoms after dentoalveolar surgery were assigned to the control group. In the ONJ group, at both T0 and T1, the mean tartrate-resistant acid phosphatase isoform 5b (TRACP 5b) levels were significantly lower and the mean Dickkopf-related protein 1 (DKK1) levels were significantly higher than the corresponding values for the control group. Linear mixed model analysis revealed significant group effects over time for serum TRACP 5b and DKK1 after adjusting for demographic, pharmacological, and diagnostic variables. Lower serum levels of TRACP 5b under a specified cut-off value (≤ 2.899 U/L) at T0 indicated a 20.40-fold increased risk of ONJ development. CONCLUSION: Patients with abnormally low serum levels of TRACP 5b and high serum levels of DKK1 should be monitored closely before and after dentoalveolar surgery for the prevention and early diagnosis of ONJ.

Association of Vitamin D Deficiency with Diabetic Nephropathy.

BACKGROUND: Low 25-hydroxyvitamin D (25OHD) levels are associated with the incidence of type 2 diabetes mellitus (T2DM). However, the association between 25OHD and metabolic health status or diabetic complications is inconclusive. We evaluated this relationship between vitamin D status and metabolic parameters and complications of T2DM. METHODS: This study included 1,392 patients with T2DM who visited Eulji and Ewha Diabetes Center between January 2011 and August 2016. Anthropometric parameters and laboratory tests including glycated hemoglobin (HbA1c), lipid profile, liver and kidney function, and urinary albumin-to-creatinine ratio (UACR) were evaluated. Diabetic macro- and microvascular complications were determined through a medical record review. Serum 25OHD concentrations were measured by chemiluminescent immunoassay. RESULTS: The mean 25OHD level was 16.8±9.6 ng/mL. Vitamin D deficiency (<20 ng/mL) and severe deficiency (<10 ng/mL) were observed in 990 (71.1%) and 351 (25.2%) participants, respectively. 25OHD level was positively correlated with age and highdensity lipoprotein cholesterol (HDL-C) level and negatively correlated with HbA1c, triglyceride level, and UACR. HDL-C and UACR were significantly associated with 25OHD after adjusting for other variables. Vitamin D deficiency was independently related to nephropathy after adjusting for confounding variables. CONCLUSION: Vitamin D deficiency was common among Korean T2DM patients; it was independently associated with microalbuminuria and HDL level, and positively related to diabetic nephropathy.

Recent Trends in Creatinine Assays in Korea: Long-Term Accuracy-Based Proficiency Testing Survey Data by the Korean Association of External Quality Assessment Service (2011-2019).

BACKGROUND: Accurate serum creatinine (Cr) concentration measurement is essential for evaluating kidney function. In 2011, the Korean Association of External Quality Assessment Service (KEQAS) launched an accuracy-based Cr proficiency testing (ABCr PT) survey. We analyzed long-term data of the KEQAS ABCr PT survey collected between 2011 and 2019 to assess recent trends in Cr assays in Korea. METHODS: The ABCr PT survey including three commutable fresh-frozen serum samples was performed twice a year. The target Cr concentration was assigned using isotope-dilution mass spectrometry. We analyzed data obtained from the participating laboratories, calculated the yearly bias, and evaluated bias trends for the major reagents and instruments. Outliers were excluded from all analysis. RESULTS: The mean percentage bias based on the total data of all participating laboratories was 10.8% in the 2011-A survey and 0.2% in 2019-B survey. Bias for the major reagents and instruments differed depending on the manufacturer. Enzymatic assays generally showed desirable bias ranging from -3.9% to 3.2% at all Cr concentrations and lower interlaboratory variability than non-enzymatic assays (enzymatic vs. non-enzymatic, 3.3%-7.2% vs. 6.3%-9.1%). CONCLUSIONS: Although the mean percentage bias of Cr assays tends to decrease over time, it is necessary to continuously strive to improve Cr assay accuracy, especially at low concentrations.

False-positive flag of WBC and change of mean platelet volume (MPV) caused by K3-EDTA on the DxH 900 hematology analyzer.

During the evaluation of the DxH 900 hematology analyzer (Beckman Coulter, Miami, FL), we noted that some patient samples produced a false positive white blood cell (WBC) flag, neutrophil blasts (NE-blast), despite the absence of abnormal cells. We investigated whether storage time or anticoagulants such as K2- or K3-ethylenediaminetetraacetic acid (EDTA) would affect complete blood count (CBC) tests on the DxH 900. Sixty-four whole blood samples were collected in K3-EDTA tubes, and 44 were simultaneously drawn in K2-EDTA tubes. Samples were tested at the following two intervals: within 30 min of collection (0 min) and after an additional 30 min of roller-mixing at room temperature (30 min). WBC differential dataplots in 0-min K3-EDTA tubes showed a mixed cell population between lymphocytes and neutrophils in 22 patients presenting the NE-blast flag. All 22 samples revealed normal WBC differential dataplots after 30 min of roller-mixing. The significantly lower mean neutrophil volume in specimens of 0-min K3-EDTA tubes than those of 0-min K2-EDTA, 30-min K2-EDTA and 30-min K3-EDTA tubes appear to be the cause of the false flag. Unlike blood cell counts, mean platelet volume (MPV) was significantly higher at 30 min using both EDTA tubes than that at 0 min. In conclusion, K3-EDTA can produce a false positive flag, NE-blast, on the DxH 900. MPV increases over time irrespective of EDTA salt type.

Performance Evaluation of the Third-Generation Elecsys FT4 III Assay for Free Thyroxine.

BACKGROUND: Roche Diagnostics has recently released the Elecsys FT4 III, Roche's third-generation reagent for free thyroxine. We aim to evaluate the analytical performance of the Elecsys FT4 III. METHODS: The precision and linearity of the Elecsys FT4 III assay were evaluated according to Clinical and Laboratory Standards Institute procedures. The results of the third-generation assay were compared with that of Roche's second-generation assay (Elecsys FT II) on a Roche cobas e801 modular analyzer. RESULTS: The coefficient of variation of within-laboratory variation was less than 2.6% for the control materials and patient samples. The linearity was confirmed over a range of 0.41 to 7.52 ng/dL. The mean difference between the second- and third-generation reagents was 0.0026 ng/dL (95% confidence interval, -0.0172 to +0.0224 ng/dL). CONCLUSIONS: The analytical performance of the Elecsys FT4 III assay for free thyroxine is clinically acceptable.

Performance Evaluation of the Elecsys Growth Hormone and Insulin-Like Growth Factor 1 Assay.

BACKGROUND: Growth hormone (GH) and insulin-like growth factor 1 (IGF-1) are important biomarkers for diagnosis and follow-up of growth-related disorders. Performance of Elecsys hGH and Elecsys IGF-1 (Roche Diagnostics) was evaluated. METHODS: The performance of the Elecsys hGH and Elecsys IGF-1 assays on a Roche Cobas e 801 modular analyzer were evaluated. Repeatability, within-laboratory imprecision, and linearity were assessed. Elecsys hGH was compared to hGH [I-125] IRMA (Izotop), and Elecsys IGF-1 was compared to IRMA IGF-1 (Immunotech). RESULTS: The coefficient of variation of within-laboratory imprecision for Elecsys hGH and IGF-1 was less than 1.7%. The linearity values for Elecsys hGH and IGF-1 were confirmed over a range of 0.05 - 24.70 ng/mL and 40.41 - 687.53 ng/mL, respectively. The mean difference between Elecsys hGH and IRMA, and Elecsys IGF-1 and IRMA was 0.284 ng/mL and 14.21 ng/mL, respectively. CONCLUSIONS: The analytical performance of Elecsys hGH and Elecsys IGF-1 was clinically acceptable.

Sample size and rejection limits for detecting reagent lot variability: analysis of the applicability of the Clinical and Laboratory Standards Institute (CLSI) EP26-A protocol to real-world clinical chemistry data.

Objectives: To maintain the consistency of laboratory test results, between-reagent lot variation should be verified before using new reagent lots in clinical laboratory. Although the Clinical and Laboratory Standards Institute (CLSI) document EP26-A deals with this issue, evaluation of reagent lot-to-lot difference is challenging in reality. We aim to investigate a practical way for determining between-reagent lot variation using real-world data in clinical chemistry. Methods: The CLSI EP26-A protocol was applied to 83 chemistry tests in three clinical labs. Three criteria were used to define the critical difference (CD) of each test as follows: reference change value and total allowable error, which are based on biological variation, and acceptable limits by external quality assurance agencies. The sample size and rejection limits that could detect CD between-reagent lots were determined. Results: For more than half of chemistry tests, reagent lot-to-lot differences could be evaluated using only one patient sample per decision level. In many cases, the rejection limit that could detect reagent lot-to-lot difference with ≥90% probability was 0.6 times CD. However, the sample size and rejection limits vary depending on how the CD is defined. In some cases, impractical sample size or rejection limits were obtained. In some cases, information on sample size and rejection limit that met intended statistical power was not found in EP26-A. Conclusions: The CLSI EP26-A did not provide all necessary answers. Alternative practical approaches are suggested when CLSI EP26-A does not provide guidance.

Proposal of Efficient Workflows for Confirmatory Neutralization Test for Initial Hepatitis B Surface Antigen Positive Samples.

BACKGROUND: Since more sensitive immunoassays have been introduced, false positive Hepatitis B surface antigen (HBsAg) results are increasing. This study was carried out to propose a process to reduce the burden of the laboratory while increasing positive predictive value in HBsAg. METHODS: Samples with Elecsys HBsAg II (Roche Diagnostics, Germany) between cutoff index (COI) 0.9 and 10.0 were tested with Elecsys HBsAg Confirmatory Test (Roche Diagnostics). If the COI value after neutralization is less than or equal to 60% of the COI treated with control reagent, the sample was determined as HBsAg positive. RESULTS: A total of 133 samples were analyzed and 70.7% were confirmed positive. The highest COI of negatively confirmed sample was 5.6. Receiver operating characteristic curve analysis of HBsAg assay showed an area under curve of 0.761. Specificity was 100% at COI 6.0. CONCLUSIONS: Based on this finding, the authors propose that only samples with HBsAg COI less than 6.0 need confirmatory tests.