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.

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.

Usefulness and performance evaluation of serum KL-6 and SP-A assays in healthy individuals and patients with interstitial lung disease

BACKGROUND

Interstitial lung abnormalities (ILAs) are associated with the risk of progression to interstitial lung diseases (ILDs). Krebs von den Lungen 6 (KL-6) and surfactant protein (SP)-A have been used as biomarkers of ILDs. In this study, we evaluated the levels of these biomarkers and identified their clinical correlations in healthy individuals to assess their usefulness in the diagnosis of ILAs.

METHODS

The patient samples were categorized into three groups: healthy, disease, and ILD groups. We used the automated immunoassay HISCL KL-6 and SP-A assay kits. The analytical performance evaluation involved precision, linearity, comparison, establishment of reference intervals, and determination of the cutoff points. We also analyzed the correlations between presence of abnormalities on chest radiography and computed tomography (CT) or pulmonary function test (PFT) and serum levels in the healthy group.

RESULTS

KL-6 and SP-A assays showed good analytical performance. The KL-6 and SP-A cutoff values were 304 U/mL and 43.5 ng/mL between the ILD and healthy groups, respectively, which were lower than the values recommended by the manufacturer. In the clinical correlations with radiological findings, SP-A values in subjects with lung abnormalities on CT scans were significantly higher than those in normal scans. There was no significant difference in KL-6 and SP-A levels among PFT patterns; however, both serum levels in the mixed pattern showed higher values than those in the other patterns.

CONCLUSIONS

The results revealed a positive association between increased serum levels of SP-A and KL-6 and clinical characteristics as incidental findings on chest imaging and reduced lung function.

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.

Total PSA Test Performance Evaluation on Cobas Pure and Measurement System Comparison with Different Calibrators

BACKGROUND

This study investigated the performance evaluation of total prostate specific antigen (tPSA) testing using Cobas Pure integrated solutions system (calibrated against WHO IS 96/670) and the comparison with established measurement systems with different traceability.

METHODS

The evaluation was performed in terms of imprecision, linearity, detection limit, and correlation with Alinity i (calibrated against WHO IS 96/670) and Unicel DxI 800 (calibrated against the manufacturer's working calibrators).

RESULTS

Within-laboratory reproducibility and repeatability were observed less than 1.2%. Linearity was achieved within the claimed analytical measurement range. The claimed LoB and LoD were experimentally verified. All the correlation coefficients among the assays indicated good correlation, but the significant mean bias with Unicel DxI 800 using a different calibrator were observed.

CONCLUSIONS

Since the tPSA calibrators against different traceability is still commercially available, our research could convey the impact of calibration on tPSA results as well as the performance information of a new assay for tPSA.

Intuitive Modification of the Friedewald Formula for Calculation of LDL-Cholesterol

Background

High LDL-cholesterol (LDL-C) is an established risk factor for cardiovascular disease and is considered an important therapeutic target. It can be measured directly or calculated from the results of other lipid tests. The Friedewald formula is the most widely used formula for calculating LDL-C. We modified the Friedewald formula for a more accurate and practical estimation of LDL-C.

Methods

Datasets, including measured triglyceride, total cholesterol, HDL-cholesterol, and LDL-C concentrations were collected and assigned to derivation and validation sets. The datasets were further divided into five groups based on triglyceride concentrations. In the modified formula, LDL-C was defined as total cholesterol - HDL-cholesterol - (triglyceride/adjustment factor). For each group, the adjustment factor that minimized the difference between measured LDL-C and calculated LDL-C using modified formula was obtained. For validation, measured LDL-C and LDL-C calculated using the modified formula (LDL-CM), Friedewald formula (LDL-CF), Martin-Hopkins formula (LDL-CMa), and Sampson formula (LDL-CS) were compared.

Results

In the derivation set, the adjustment factors were 4.7, 5.9, 6.3, and 6.4 for the groups with triglyceride concentrations <100, 101-200, 201-300, and >300 mg/dL, respectively. In the validation set, the coefficient of determination (R²) between measured and calculated LDL-C was higher for LDL-CM than for LDL-CF (R²=0.9330 vs. 0.9206). The agreement according to the National Cholesterol Education Program Adult Treatment Panel III classification of LDL-C was 86.36%, 86.08%, 86.82%, and 86.15% for LDL-CM, LDL-CF, LDL-CMa, and LDL-CS, respectively.

Conclusions

We proposed a practical, improved LDL-C calculation formula by applying different factors depending on the triglyceride concentration.

Age Group-specific Reference Intervals for the Elecsys Anti-Müllerian Hormone Assay in Healthy Korean Women: a Nationwide Population-based Study

Background

Anti-Müllerian hormone (AMH) is one of the most reliable markers of ovarian reserve. Automated AMH assays are widely used in clinical laboratories, but reference intervals for the Elecsys AMH assay for Asian populations have not yet been determined. We aimed to determine reference intervals in healthy Korean women.

Methods

The study included 1,450 women aged 19 to 54 years who participated in the Korea National Health and Nutrition Examination Survey between 2013 and 2016. The study participants were divided into seven 5-year age groups. AMH and progesterone concentrations were measured using Roche Elecsys assays, and bone morphogenetic protein-15 (BMP15) was genotyped for the detection of major variants. Age group-specific reference intervals for AMH were established as recommended by the CLSI EP28-A3c guidelines.

Results

The mean age was 37.4 years. AMH concentrations decreased with increasing age, especially after 40 years, with the median AMH decreasing from 30.9 pmol/L in participants of 19-24 years to 0.071 pmol/L in participants of 50-54 years. The mid-95 percentile AMH reference intervals decreased from 7.93-81.21 pmol/L in participants of 19-24 years to 0.07-3.86 pmol/L in participants of 50-54 years. Disease-associated BMP15 variants were not detected.

Conclusions

We determined Elecsys AMH assay reference intervals in healthy Korean women. The results may provide basic information for the interpretation of AMH concentrations and assessment of ovarian reserve in Korean women.

Practical Considerations for Clinical Laboratories in Top-down Approach for Assessing the Measurement Uncertainty of Clinical Chemistry Analytes

Background

The top-down (TD) approach using internal quality control (IQC) data is regarded a practical method for estimating measurement uncertainty (MU) in clinical laboratories. We estimated the MU of 14 clinical chemistry analytes using the TD approach and evaluated the effect of lot changes on the MU.

Methods

MU values were estimated using subgrouping by reagent lot changes or using the data as a whole, and both methods were compared. Reagent lot change was simulated using randomly generated data, and the mean values and MU for two IQC datasets (different QC material lots) were compared using statistical methods.

Results

All MU values calculated using subgrouping were lower than the total values; however, the average differences were minimal. The simulation showed that the greater the increase in the extent of the average shift, the larger the difference in MU. In IQC data comparison, the mean values and MU exhibited statistically significant differences for most analytes. The MU calculation methods gave rise to minimal differences, suggesting that IQC data in clinical laboratories show no significant shift. However, the simulation results demonstrated that notable differences in the MU can arise from significant variations in IQC results before and after a reagent lot change. Additionally, IQC material lots should be treated separately when IQC data are collected for MU estimation.

Conclusions

Lot changes in IQC data are a key factor affecting MU estimation and should not be overlooked during MU estimation.

Strategies to shorten turnaround time in outpatient laboratory

BACKGROUND

Turnaround time (TAT) is one of the most important indicators of laboratory quality. For the outpatient routine chemistry tests whose results are checked by clinicians on the same day, we set a quality goal that >90% of these samples should be reported within 60 min. As more than 20% of the samples failed to achieve this goal in 2020, we introduced an additional autoanalyzer and a real-time monitoring system to improve this rate.

METHODS

As the TAT of the pre-analytical phase is the greatest contributor to TAT, we divided it into sampling, sample transport, and sample preparation times. An additional autoanalyzer was introduced, and its effect on TAT improvement was evaluated with the TAT data of June and July 2020. A real-time monitoring system was introduced to sort delayed samples, and its effect was assessed with the TAT data of June and July 2021. TAT data from December 2019 to January 2020 were set as baseline controls.

RESULTS

The preparation time comprised the largest proportion of TAT. Although there was a slight decrease in overall TAT after the introduction of the above two strategies, the target TAT achievement rate increased significantly from 78.5% to 88.7% (p < 0.001).

CONCLUSIONS

We checked the cause of TAT prolongation and introduced new strategies to improve it. The addition of an autoanalyzer per se was not so effective but was better when combined with the real-time monitoring system. Such strategies would increase the quality of the laboratory services.

A New Trial to Measure ABO Antibodies Using Complement-Dependent Cytotoxicity

Background and objectives: The ABO antibody (Ab) titration tests are used in monitoring in ABO-incompatible (ABOi) solid organ transplantation (SOT). However, currently developed ABO Ab tests show Ab binding reactions. This study attempted to measure ABO Ab level using complement-dependent cytotoxicity (CDC). Materials and methods: We studied 93 blood group O serum samples from patients who underwent ABOi SOT from January 2019 to May 2021. Patients’ sera were incubated with A1 or B cells and added to a human complement solution. Supernatants were collected after centrifugation, and free hemoglobin (Hb) was measured by spectrophotometry. We converted plasma Hb value to hemolysis (%), which were compared with ABO Ab titer. Results: We found a mild correlation between hemolysis and ABO Ab titers. In simple regression analysis, the correlation coefficients were within 0.3660−0.4968 (p < 0.0001) before transplantation. In multiple linear regression analysis, anti-A hemolysis (%) was higher in immunoglobulin M (IgM) (β = 12.9) than in immunoglobulin G (IgG) (β = −3.4) (R2 = 0.5216). Anti-B hemolysis was higher in IgM (β = 8.7) than in IgG (β = 0.0) (R2 = 0.5114). There was a large variation in hemolysis within the same Ab titer. Conclusions: CDC can be used in a new trial for ABO Ab measurement. Furthermore, IgM rather than IgG seems to play a significant role in vivo activity, consistent with previous knowledge. Thus, this study may help in the development of the ABO Ab titration supplement test for post-transplant treatment policy establishment and pre-transplant desensitization.

Effect of Outlier Elimination on the 99th Percentile Upper Reference Limits of High-Sensitivity Cardiac Troponin I Assays Based on a Strictly Selected Healthy Reference Population

Background

We established high-sensitivity cardiac troponin I (hsTnI) 99th percentile upper reference limits (URLs) for the Centaur XPT High-Sensitivity Troponin I assay (Centaur hsTnI; Siemens, Erlangen, Germany) and Atellica IM High-Sensitivity Troponin I assay (Atellica hsTnI; Siemens) and assessed the effect of outlier elimination.

Methods

The reference population comprised 380 men and 387 women, satisfying the strict systematic reference population criteria. After reference population verification by the N-terminal pro-B-type natriuretic peptide (NT-proBNP) assay, 99th percentile URLs for Centaur hsTnI and Atellica hsTnI were calculated before and after outlier elimination.

Results

The 99th percentile URL for Centaur hsTnI was 60.4 (men, 74.7; women, 57.5) ng/L and that for Atellica hsTnI was 59.6 (men, 75.2; women, 55.1) ng/L. After the elimination of 61 (8.0%) outlier samples in Centaur hsTnI and 58 (7.6%) in Atellica hsTnI, the 99th percentile URLs were 13.5 ng/L (men, 15.3 ng/L; women, 11.9 ng/L) and 13.4 ng/L (men, 15.5 ng/L; women, 12.9 ng/L), respectively, significantly lower than those before outlier elimination. The CVs at the 99th percentile URLs were 5.2% and 3.5%, respectively. The measurable fractions among the reference population were 91.5% and 93.4%, respectively. Performance evaluation of Atellica B-type natriuretic peptide (BNP), Atellica NT-proBNP, Centaur hsTnI, and Atellica hsTnI showed outstanding results.

Conclusions

The Korean hsTnI 99th percentile URLs calculated in this study were significantly lower after outlier elimination than before. Centaur hsTnI and Atellica hsTnI meet the "Guideline acceptable" and "Level 3 (second generation, high sensitivity)" requirements, satisfying international standards.

OUP accepted manuscript

Objective

This study aimed to examine the intra- and interlaboratory variations of cycle threshold (Ct) values using the nationwide proficiency testing for SARS-CoV-2.

Methods

Triplicated strong-positive contrived samples duplicated weak-positive contrived samples, and 2 negative samples were transported to participating laboratories in October 2021.

Results

A total of 232 laboratories responded. All except 4 laboratories correctly answered. Six false-negative results, including 2 false-negatives with Ct values beyond the threshold and 1 clerical error, were noted from weak-positive samples. Intralaboratory variations of Ct values of weak-positive and strong-positive samples were not acceptable (Ct > 1.66) in 17 and 7 laboratories, respectively. High interlaboratory variations of Ct values (up to 7 cycles) for the 2 commonly used polymerase chain reaction (PCR) reagents were observed.

Conclusion

The overall qualitative performance was acceptable; intralaboratory variation was acceptable. However, interlaboratory variations of Ct values were remarkable even when the same PCR reagents were used.

Semiquantitative Analysis of the Results of an Image-Based Urine Sediment Analyzer Considering the Preanalytical Factors

BACKGROUND

Automated microscopic platforms are increasingly used in clinical laboratories for rapid analysis of samples. However, it is important to present the results quantitatively or semiquantitatively because automated platforms use various technologies for analysis as well as different sediment preparation methods. The results of cell counting using an on screen image review program for the cobas u 701 analyzer (Roche Diagnostics Interna-tional, Rotkreuz, Switzerland) differed from those obtained by manual microscopic examination (MME). This study was performed to investigate the difference of results among analyzer, on-screen image review and MME.

METHODS

Freshly collected urine specimens from outpatients were used. We calculated the mean, standard deviation, and 95% confidence interval for red and white blood cell (RBC/WBC) quantitative results obtained using the cobas u 701 analyzer. These results were compared to those obtained by manual counting. RBC and WBC counts determined with the cobas u 701 analyzer were compared to those obtained by MME per unit field.

RESULTS

The semiquantitative results of MME were graded as 0 - 2, 3 - 5, 6 - 10, 11 - 20, 21 - 30, and many or numerous cells/high power field (HPF). The RBC and WBC counts determined by image analyses showed the tendency to be one grade higher than those from MME in the range of 3 to 5/HPF to many/HPF. The results of nearly all samples with 0 - 2/HPF and numerous/HPF for RBC and WBC counts were consistent with the grade found by MME.

CONCLUSIONS

The one-grade difference may have been caused by the differences of preanalytical factors in the sample volume, centrifugal force, urine concentration ratio, or sediment volume/area of the slide. When reporting the results of image analyses, RBC and WBC counts should be raised by one grade to compensate for MME. Each laboratory needs to verify the on-screen review of images corresponding to the microscopic field of view according to the clinical laboratory's specific preanalytical practices.

Schemes and Performance Evaluation Criteria of Korean Association of External Quality Assessment (KEQAS) for Improving Laboratory Testing

External quality assessment (EQA) is important for evaluating clinical laboratories and enhancing their testing quality. EQA schemes are variable; thus, it is crucial that the EQA organizers share their experiences to continuously improve the EQA scheme. The Korean Association of External Quality Assessment Service (KEQAS) has been the leading, authorized EQA institute for the standardization and quality management of laboratory testing in Korean medical institutions since 1976. The EQA scheme underwent a major change in 2016, and the number of EQA programs increased significantly since then. The key changes implemented in EQA scheme include a fully computerized assessment to accelerate feedback and unification of the testing and reporting methods. We provide an overview of the EQA schemes and performance evaluation criteria of the KEQAS and suggest directions for achieving the global harmonization of EQA.

Standardization Status of Total Cholesterol Concentration Measurement: Analysis of Korean External Quality Assessment Data

Background

Total cholesterol concentration measurement is important in the diagnosis of dyslipidemia and evaluation of cardiovascular disease risk factors. Measurement reliability for obtaining an accurate total cholesterol concentration requires procedure standardization. We evaluated the standardization status for total cholesterol concentration measurement through Korean external quality assessment (EQA) data analysis.

Methods

This study involved 1,670 laboratories that participated in the EQA of total cholesterol concentration measurements in 2019 for 32 products from different manufacturers. The target concentrations of three quality control (QC) materials (samples A, B, and C) were measured using the reference method and compared with EQA data. The performance criteria for total cholesterol concentration measurement were based on the National Cholesterol Education Program guidelines, with ±3% inaccuracy.

Results

The target values and inaccuracies of the QC material based on the reference method measurements were 254.65±7.64, 108.30±3.25, and 256.29±7.69 mg/dL (6.59±0.20, 2.80±0.08, and 6.63±0.20 mmol/L) for samples A, B, and C, respectively. The performance criteria were not met in 42.7% laboratories for sample A, 68.4% of laboratories for sample B, and 38.0% laboratories for sample C.

Conclusions

Despite significant efforts to accurately measure total cholesterol concentrations, further actions are needed for measurement standardization. Manufacturers reporting values that differ from target values should check calibrator traceability; additional efforts to accurately measure total cholesterol concentrations are required for laboratories that use products from these manufacturers.

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.

Status of Four Trace Elements in Elderly Patients with Online Hemodiafiltration

BACKGROUND

Essential trace elements play key roles in multiple biological systems, and hemodialysis patients are at risk for deficiency of essential trace elements. The aim of the study was to assess the essential element status in end stage renal disease patients undergoing online hemodiafiltration (online HDF) in outpatient dialysis clinic.

METHODS

A total of 28 Korean patients with regular online HDF were included. Blood samples were collected before and after one HDF session, and serum concentrations of zinc, copper, selenium, and manganese were simulta-neously measured by inductively coupled plasma mass spectrometry.

RESULTS

Selenium, zinc, copper deficiencies were observed in 71.4%, 35.8%, and 21.4%, compared with the reference range. No patients revealed manganese deficiency. After the HDF, the post-HDF level significantly increased in all trace elements, compared with the pre-HDF (11.2% for selenium, 10.7% for copper, and 6.6% for zinc). However, 50% patients were still deficient for selenium at the post-HDF.

CONCLUSIONS

Our data suggest that the patients undergoing online HDF are at an increased risk of trace element deficiency, especially for selenium.

Nationwide External Quality Assessment of SARS-CoV-2 Molecular Testing, South Korea

External quality assessment (EQA) is essential for ensuring reliable test results, especially when laboratories are using assays authorized for emergency use for newly emerging pathogens. We developed an EQA panel to assess the quality of real-time reverse transcription PCR assays being used in South Korea to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). With the participation of 23 public health organization laboratories and 95 nongovernmental laboratories involved in SARS-CoV-2 testing, we conducted qualitative and semiquantitative performance assessments by using pooled respiratory samples containing different viral loads of SARS-CoV-2 or human coronavirus OC43. A total of 110 (93.2%) laboratories reported correct results for all qualitative tests; 29 (24.6%) laboratories had >1 outliers according to cycle threshold values. Our EQA panel identified the potential weaknesses of currently available commercial reagent kits. The methodology we used can provide practical experience for those planning to conduct evaluations for testing of SARS-CoV-2 and other emerging pathogens in the future.

The Frequency of Discordant Variant Classification in the Human Gene Mutation Database: A Comparison of the American College of Medical Genetics and Genomics Guidelines and ClinVar

OBJECTIVE

Discordant variant classifications among public databases is one of the well-documented limitations when interpreting the pathogenicity of variants. The aim of this study is to investigate the level of germline variant misannotation from the Human Gene Mutation Database (HGMD) and the annotation concordance between databases.

METHODS

We used a total of 188,106 classified variants (disease-causing mutations [n = 179,454] and polymorphisms [n = 8652]) in 6466 genes from the HGMD. All variants were reanalyzed based on the American College of Medical Genetics and Genomics (ACMG) guidelines and compared to ClinVar database variants.

RESULTS

When variants were classified based on the ACMG guidelines, misclassification was observed in 3.47% (2289/65,896) of variants. The overall concordance between HGMD and ClinVar was 97.62% (52,499/53,780) of variants studied.

CONCLUSION

Variants in databases must be used with caution when variant pathogenicity is interpreted. This study reveals the frequency of misannotation of the HGMD variants and annotation concordance between databases in depth.

Development of fluorescent Escherichia coli for a whole-cell sensor of 2'-fucosyllactose

2′-Fucosyllactose (2′-FL), a major component of fucosylated human milk oligosaccharides, is beneficial to human health in various ways like prebiotic effect, protection from pathogens, anti-inflammatory activity and reduction of the risk of neurodegeneration. Here, a whole-cell fluorescence biosensor for 2′-FL was developed. Escherichia coli (E. coli) was engineered to catalyse the cleavage of 2′-FL into l-fucose and lactose by constitutively expressing α-l-fucosidase. Escherichia coli ∆L YA, in which lacZ is deleted and lacY is retained, was employed to disable lactose consumption. E. coli ∆L YA constitutively co-expressing α-l-fucosidase and a red fluorescence protein (RFP) exhibited increased fluorescence intensity in media containing 2′-FL. However, the presence of 50 g/L lactose reduced the RFP intensity due to lactose-induced cytotoxicity. Preadaptation of bacterial strains to fucose alleviated growth hindrance by lactose and partially recovered the fluorescence intensity. The fluorescence intensity of the cell was linearly proportional to 1–5 g/L 2′-FL. The whole-cell sensor will be versatile in developing a 2′-FL detection system.

Complete genome sequence of Paenibacillus xylanexedens PAMC 22703, a xylan-degrading bacterium

Paenibacillus is widely distributed in various environments and has the potential for use as a biotechnological agent in industrial processes. Here, we report the complete genome sequence of the marine bacterium, Paenibacillus xylanexedens PAMC 22703, which utilizes xylan. The P. xylanexedens PAMC 22703 strain was isolated from marine sediments. P. xylanexedens PAMC 22703 utilizes xylan as a carbon source to grow. The genome sequence clarified that this strain possesses genes for utilizing xylan. The complete genome sequence contained one chromosome (7,053,622 bp with 46.0% GC content) and one plasmid (44,617 bp with 44.1% C + G content). The genome harbored genes that fully deploy the xylan assimilation pathway. The complete genome sequence of P. xylanexedens PAMC 22703 would prove useful in acquiring information for its application with xylan in various industries.

Improved production of 3-hydroxypropionic acid in engineered Escherichia coli by rebalancing heterologous and endogenous synthetic pathways

To improve 3-hydroxypropionic acid (3-HP) production by Escherichia coli, glycerol accumulation needs to be reduced. To accomplish this, we constructed a novel E. coli strain that overexpresses the endogenous aldehyde dehydrogenase gene (puuC) under the control of a strong promoter. The fermentation performance of the engineered strain was significantly improved compared to that of the parental control strain in the presence of glucose and xylose. We also inactivated the puu operon repressor gene, puuR, which resulted in a decrease in glycerol accumulation and an increase in 3-HP production through the co-fermentation of glucose and xylose. Through fed-batch fermentation by utilizing glucose and xylose, the engineered strain, JHS_Δgypr-PT7, produced 53.7 g/L 3-HP and accumulated 1.5 g/L glycerol. This combination strategy, wherein we overexpressed the endogenous puuC gene from a strong promoter and eliminate its transcriptional repression, may be extended to rebalance another biochemical pathway.

GeneReader NGS System Is a Useful Sequencing Platform for Clinical Testing of BRCA1 and BRCA2

Although next-generation sequencing (NGS) is widely used for BRCA1/2 sequencing analysis, it involves a fragmented workflow along with complex bioinformatic analysis and interpretation. In this study, the performance characteristics and workflow of the GeneReader NGS System (QIAGEN), including BRCA1/2 sequencing, were evaluated. For BRCA1/2 genetic testing, we conducted library preparation, emulsion PCR, and sequencing. QCI Analyze software was used for read alignment, quality control, variant calling, and clinical report generation. GeneReader and Sanger sequencing utilized 63 patients with breast or ovarian cancer for comparison. Reproducibility, precision, variant calling, turnaround time, and hands-on time were evaluated. The read percentage in the on-target regions was 90.5%. More than 99.99% of target regions showed read depths ≥100x. Variants generated from GeneReader showed 100% accuracy compared to the Sanger sequencing results. Annotation with GeneReader showed >99.8% concordance with HGVS nomenclature. Single-nucleotide variations and indel variants showed 100% calling reproducibility; the precision for variant frequency showed a 0.3-3.6% coefficient of variation. Most processes involved hands-off time (3714 min, 88.6% of total run time). The GeneReader NGS System for BRCA1 and BRCA2 testing showed good analytical performance and a short hands-on time. Because of its integrated sample preparation for bioinformatic interpretation, this system is practical for clinical laboratories.

Accuracy evaluation of automated electrochemiluminescence immunoassay for everolimus and sirolimus compared to liquid chromatography-tandem mass spectrometry

Background

We evaluated the analytical performance of a newly developed electrochemiluminescence immunoassay for everolimus and sirolimus compared to that of liquid chromatography‐tandem mass spectrometry (LC‐MS/MS).

Methods

According to Clinical and Laboratory Standards Institute guidelines, the analytical performance including precision, recovery, linearity, and carryover was evaluated. For correlation evaluation, the results of Elecsys^® analysis of everolimus and sirolimus were compared with those of LC‐MS/MS using 120 samples from patients treated with everolimus or sirolimus.

Results

The within‐run and total imprecision values were as follows: 2.3%‐4.5% and 4.5%‐6.4% for the everolimus assay; 3.3%‐4.8% and 4.7%‐8.1% for the sirolimus assay, respectively. The measured concentration was linear over the range of 0.718‐27.585 ng/mL for everolimus analysis and 0.789‐26.880 ng/mL for sirolimus analysis (all R² > 0.99). Recovery was 93.5%‐105.5% for the everolimus assay and 99.2%‐109.1% for the sirolimus assay (except lowest levels). Carryover was −1.09% for the everolimus assay and −0.12% for the sirolimus assay. The results of the two chemiluminescence immunoassays showed acceptable correlations with those of LC‐MS/MS (R = 0.9585 and R = 0.9799, respectively). The two immunoassays showed slightly proportional biases compared to LC‐MS/MS.

Conclusion

Elecsys^® Everolimus and Sirolimus assays showed acceptable analytical performance in precision, linearity, and correlation compared to LC‐MS/MS These methods can be adopted in the clinical laboratory for rapid therapeutic drug monitoring of patients who require treatment with immunosuppressants.

A Simple and Accurate Liquid Chromatography-Tandem Mass Spectrometry Method for Therapeutic Drug Monitoring of Busulfan in Plasma

OBJECTIVE

Busulfan, frequently used as a conditioning regimen for hematopoietic stem cell transplantation, has a narrow therapeutic range and wide intra-and interpatient variabilities. Therefore, therapeutic drug monitoring of busulfan is necessary to ensure that the drug concentrations of patients are within a targeted therapeutic range. In this study, we developed a simple and accurate method for measuring busulfan concentrations using liquid chromatography tandem mass spectrometry (LC-MS/MS).

METHODS

Separation and detection of busulfan was performed using T3 column equipped with LC-MS/MS. Busulfan was isolated from 50 μL human plasma after mixing with busulfan^-2H₈ (internal standard) solution, calibrator, and quality-control material. The sample was eluted and gradated with a mobile phase composed of ammonium acetate, formic acid, and water or methanol. The busulfan concentration was quantified using a six-point standard curve. Busulfan and busulfan^-2H₈ were detected in positive-ion multiple-reaction-monitoring mode. According to the Clinical and Laboratory Standards Institute guideline, we verified the precision, linearity, limit of detection (LOD), limit of quantification (LOQ), and carryover.

RESULTS

Busulfan and busulfan^-2H₈ were detected at m/z 264.1>151.1 and 272.2>159.1. The total run time was 3 min. Both intra-and inter-assay coefficients of variation were <3%. The calibration curve was linear at 25-5,000 ng/mL. The LOD and LOQ were 2.5 ng/mL and 25 ng/mL, respectively. The recoveries ranged from 92.0-104.8% and the carryover was-0.02%.

CONCLUSIONS

Our method for busulfan reduces total run time and has excellent analytical performance. It will be a useful method for therapeutic drug monitoring of busulfan in clinical laboratories.

Accuracy evaluation of Roche and Siemens tacrolimus and cyclosporine assays in comparison with liquid chromatography-tandem mass spectrometry

Therapeutic drug monitoring of tacrolimus and cyclosporine is crucial to the success of organ transplantation. We evaluated the analytical performances and accuracy of two commercially available tacrolimus and cyclosporine assays (Roche ISD and Siemens) in comparison with liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 342 leftover whole blood samples requested for tacrolimus or cyclosporine assays were stored at -20 °C until analysis. Repeatability and between-run imprecision were evaluated using quality control materials provided by the manufacturer. Ring trial samples were used for the assessment of recovery. The results of the Roche ISD assay were compared with those of Siemens tacrolimus and cyclosporine assays and LC-MS/MS. Repeatability and between-run imprecision were 2.1-5.3% and 2.6-7.5%, respectively. Recovery of Roche ISD was 85.7 - 90.6% for cyclosporine and 96.2-98.5% for tacrolimus. The two immunoassays showed slight positive biases relative to LC-MS/MS for cyclosporine. For tacrolimus, Roche ISD produced virtually identical results to those of LC-MS/MS, whereas Siemens showed proportional differences, especially in patients receiving kidney transplantation. The analytical performances of Roche ISD were generally acceptable, especially regarding accuracy. Clinical laboratory staff should be aware of the strengths and weaknesses of commercial immunoassays in order to ensure accurate results.

The efficient workflow to decrease the manual microscopic examination of urine sediment using on-screen review of images

BACKGROUND

The manual microscopic examination (MME) of urine sediment is labor-intensive, time-consuming, and imprecise. Therefore, automated urinalysis systems based on flow cytometry or digital imaging techniques could replace MME. The purpose of this study was to evaluate the rate of MME using two automated urine sediment analyzers, alone and in combination.

METHODS

This study was conducted using the freshly collected urine specimens of 1055 in-patients and 1119 out-patients. All samples were analyzed using UF-1000i (Sysmex Corporation) and Cobas 6500 instrument (Roche Diagnostics International). The rate of MME was evaluated using two analyzers, both individually and in combination.

RESULTS

Using the UF-1000i alone, 34.2% and 16.8%, respectively, of in- and out-patient samples were analyzed by MME, compared to 15.6% and 3.7%, respectively, using the Cobas 6500. In combined assay using the UF-1000i followed by the Cobas 6500, 27.9% and 11.3% in-patient samples required on-screen review and MME, respectively. And the respective rates were 10.3% and 2.7% of out-patient. Samples using the Cobas 6500 followed by the UF-1000i, 42.3% and 11.3% in-patient needed on-screen review and MME, respectively. And the respective rates were 18.9% and 2.7% of out-patient samples.

CONCLUSIONS

Use of the Cobas 6500 compared to the UF-1000i resulted in decreases in the rate of MME from 34.2% to 15.6% for in-patient samples, and from 16.8% to 3.7% for out-patient samples. Use of the Cobas 6500 reduced the rate of MME, and compared to use of only the Cobas 6500, the combined use resulted in a reduction in the rate of on-screen review.

Efficacy and Survival Outcome Associated with the Use of Novel Agents and Autologous Stem Cell Transplantation in Cases of Immunoglobulin D Multiple Myeloma in Korea

BACKGROUND

Immunoglobulin D multiple myeloma (IgD MM) is characterized by a poor prognosis. Data are lacking on the survival benefits associated with the use of novel agents followed by autologous stem cell transplantation (ASCT) in IgD MM patients. We evaluated the clinical outcomes of induction treatment with novel agents followed by ASCT.

METHODS

This was a single-center, retrospective study of 22 IgD MM patients who underwent ASCT between 1995 and 2016. Of these, 10 (45.4%) received novel agents and 12 (54.6%) received nonnovel agents. Clinical features and survival outcomes were examined.

RESULTS

Median overall survival (OS) was 37.7 months in the 22 patients. Those in the novel-agents group received bortezomib or thalidomide-based regimens, whereas 91.7% of the nonnovel-agents group received a vincristine-based regimen. The median progression-free survival and OS in the novel-agent/nonnovel-agent groups were 8.3/7.4 and 38.6/12.5 months, respectively. The median OS of patients receiving maintenance therapy was not reached.

CONCLUSION

This study showed improved survival outcomes compared to our previous study (37.7 vs. 12 months), suggesting that the use of a novel agent as induction and maintenance therapy may be beneficial in patients with IgD MM who undergo ASCT.

Performance of the Dimension TAC assay and comparison of multiple platforms for the measurement of tacrolimus

BACKGROUND

Therapeutic monitoring of tacrolimus is essential for reducing organ rejection and adverse effects. The measurement of tacrolimus in whole blood is taken by many automated platforms. We evaluated the analytical performance of the Dimension TAC assay, which is an upgraded reagent from the previous Dimension TACR assay.

METHODS

The evaluations involved determination of precision, linearity, detection capability, and reagent lot-to-lot variability between three lot numbers. Correlation studies were conducted using the Dimension TACR assay, Architect, Elecsys assay, and MassTrak LC-MS/MS.

RESULTS

The total coefficient of variation was below 10%. Acceptable linearity was observed in their respective reportable ranges. The limit of blank, limit of detection, and limit of quantification were 0.29, 0.47, and 0.81 ng/mL, respectively. Correlation analysis indicated that the Dimension TAC assay results were comparable to that of the Dimension TACR assay, Architect, and Elecsys results in liver and heart transplant patients. In kidney transplant patients, the Dimension TAC assay showed the poor correlation with Architect and Elecsys. The results from these assays were slightly higher than that of MassTrak. We found little lot-to-lot reagent variation among the reagents evaluated.

CONCLUSION

The overall analytical performance of the Dimension TAC assay is acceptable for therapeutic monitoring in clinical practice. Our study that compared different platforms may provide some useful information regarding which test method to use.

Efficient reporting of the estimated glomerular filtration rate without height in pediatric patients with cancer

BACKGROUND

The updated bedside Schwartz equation requires constant, serum creatinine concentration and height measurements to calculate the estimated glomerular filtration rate (eGFR) in pediatric patients. Unlike the serum creatinine levels, obtaining height information from the laboratory information system (LIS) is not always possible in a clinical laboratory. Recently, the height-independent eGFR equation, the full age spectrum (FAS) equation, has been introduced. We evaluated the performance of height-independent eGFR equation in Korean children with cancer.

METHODS

A total of 250 children who underwent chromium-51-ethylenediamine tetra acetic-acid (51Cr-EDTA)-based glomerular filtration rate (GFR) measurements were enrolled. The 51Cr-EDTA GFR was used as the reference GFR. The bias (eGFR - measured GFR), precision (root mean square error [RMSE]) and accuracy (P30) of the FAS equations were compared to those of the updated Schwartz equation. P30 was defined as the percentage of patients whose eGFR was within ±30% of the measured GFR.

RESULTS

The FAS equation showed significantly lower bias (mL/min/1.73 m2) than the updated Schwartz equation (4.2 vs. 8.7, p<0.001). The RMSE and P30 were: updated Schwartz of 43.8 and 64.4%, respectively, and FAS of 42.7 and 66.8%, respectively.

CONCLUSIONS

The height-independent eGFR-FAS equation was less biased and as accurate as the updated Schwartz equation in Korean children. The use of the height-independent eGFR equation will allow for efficient reporting of eGFR through the LIS in clinical laboratories.

A new strategy for calculating the risk of ovarian malignancy algorithm (ROMA)

BACKGROUND

Reliable quantitative measurements of HE4 and CA125 levels are required to calculate the risk of ovarian malignancy algorithm (ROMA) value. We suggest a new reporting strategy for interpreting ROMA values based on analytical measurement range (AMR) and qualified-intervals of the HE4 and CA125 results.

METHODS

HE4 and CA125 assays from Abbott and Roche were used. The AMRs and the qualified-intervals were as follows: Architect HE4 assay, 20-1500 and 17.2-2637.8 pmol/L; Architect CA125 II assay, 1-1000 and 3.9-14,163.0 U/mL; Elecsys HE4 assay, 15-1500 and 28.8-3847 pmol/L; Elecsys CA125 II assay, 0.6-5000 and 6.5-5000 U/mL. These values were used to simulate the ROMA values.

RESULTS

Reporting algorithm for the ROMA value could be classified into three categories. (1) If quantitative HE4 and CA125 levels are reliable, the numerical ROMA value can be reported. (2) If HE4 value is <20 and <28.8 for Abbott and Roche in premenopausal woman, the ROMA value should be reported as "low risk" regardless of the CA125 result. In postmenopausal woman, however, it should be reported as "low risk" (CA125<203.0 and <165.8 for Abbott and Roche) or "undetermined" (vice-versa value). (3) If CA125 value is <3.9 and <6.5 for Abbott and Roche, it should be reported as "low risk" (premenopausal HE4<51.5 and <62.2, postmenopausal HE4<323.0 and <281.5 for Abbott and Roche) or "undetermined" (vice-versa value).

CONCLUSIONS

New reporting strategy will provide more informative reporting of ROMA values in clinical practice.

Large-scale performance evaluation of Accu-Chek inform II point-of-care glucose meters

BACKGROUND

The aim of this study was to report the experience of large-scale performance evaluation of 238 Accu-Chek Inform II point-of-care (POC) glucose meters in a single medical setting.

METHODS

The repeatability of 238 POC devices, the within-site imprecision of 12 devices, and the linearity of 49 devices were evaluated using glucose control solutions. The glucose results of 24 POC devices and central laboratory were compared using patient samples.

RESULTS

Mean concentration of control solutions was 2.39 mmol/L for Level 1 and 16.52 mmol/L for Level 2. The pooled repeatability coefficient of variation (CV) of the 238 devices was 2.0% for Level 1 and 1.6% for Level 2. The pooled within-site imprecision CV and reproducibility CV of the 12 devices were 2.7% and 2.7% for Level 1, and 1.9%, and 1.9% for Level 2, respectively. The test results of all 49 devices were linear within analytical measurement range from 1.55-31.02 mmol/L. The correlation coefficient for individual POC devices ranged from 0.9967-0.9985. The total correlation coefficient for the 24 devices was 0.998.

CONCLUSIONS

The Accu-Chek Inform II POC blood glucose meters performed well in terms of precision, linearity, and correlation evaluations. Consensus guidelines for the large-scale performance evaluations of POC devices are required.

Lack of association between oxidized LDL-cholesterol concentrations and haptoglobin phenotypes in healthy subjects

Background: The haptoglobin (Hp) 2-2 phenotype has been known to have less antioxidative activity than Hp 1-1 and Hp 2-1. However, few have reported the relationship between oxidative stress and Hp phenotypes by using oxidized LDL. The relationship between Hp phenotypes and oxidative stress was therefore investigated in healthy adults.

Methods: The serum Hp concentrations, albumin, uric acid, iron, L-ascorbic acid, total antioxidant status and oxidized LDL concentrations were measured and analysed in 200 healthy Korean men and women with Hp 2-1 and Hp 2-2 phenotypes.

Results: The serum concentrations of Hp were significantly higher in the Hp 2-1 compared with the Hp 2-2 phenotype. However, serum concentrations of total antioxidant status and oxidized LDL did not show any statistical differences in either sex. The L-ascorbic acid concentrations in serum showed lower values in the Hp 2-2 compared with the Hp 2-1 phenotype, for both sexes ( P < 0.05).

Conclusions: The concentration of L-ascorbic acid, the first line antioxidant, was lower in the Hp 2-2 than in the Hp 2-1 phenotype; this did not significantly affect the total antioxidant status, and there was no significant difference in oxidized LDL for either group in healthy adults.

The effects of green tea ingestion over four weeks on atherosclerotic markers

Background: The objective of this study was to evaluate the effects of green tea ingestion over four weeks on atherosclerotic biological markers.

Methods: After a one-week baseline period, 12 healthy male volunteers aged 28-42 years drank 600 mL of green tea dailyfor four weeks. Lipid profile, oxidized low-density lipoprotein (ox-LDL), total antioxidant capacity (TAC), C-reactive protein (CRP) and soluble cell adhesion molecules were measured at baseline and after two and four weeks ingestion of green tea.

Results: There was no significantchange in the concentrations of lipid profile, TAC, CRP, soluble intercellular adhesion molecule-1 (sICAM-1), or soluble E-selectin after ingestion of green tea. The levels of ox-LDL and soluble vascular cell adhesion molecule-1 (sVCAM-1) were significantly decreased after four weeks of green tea ingestion (Wilcoxon signed rank test, P=0.006).

Conclusions: The results of this study suggest an in vivo anti-oxidative effect for green tea and an influence of green tea on atherosclerotic biological markers. The effect of green tea seen on ox-LDL and sVCAM-1provides a potential mechanism for the cardiovascular benefits of regular ingestion of green tea.

Affinity improvement by fine tuning of single-chain variable fragment against aflatoxin B1

Aflatoxin B1 (AFB1) produced in Aspergillus flavus is a major hepatocarcinogen found in foods and feed. For effective immunological detection of AFB1 at low concentrations, the development of high affinity antibody for AFB1 is required. Previously, an affinity-maturated single-chain variable fragment containing 6 mutations (scFv-M37) was isolated from an artificial mutagenic library, which showed a 9-fold higher affinity than its wild type scFv. In this study, the effect of the 6 mutated residues on the affinity improvement was characterized using surface plasmon resonance analysis, which identified a deleterious mutation (VH-A110T) located on a framework region of the scFv-M37. The back mutation of VH-A110T resulted in a 3.2-fold affinity improvement, which was attributed to decrease of dissociation rate constant (kd) in interaction between AFB1 and the back mutant scFv. The biophysical analyses using circular dichroism and gel filtration revealed that the back mutation of VH-A110T caused a subtle conformational change of the scFv toward tighter binding to AFB1.

Performance Evaluation of a Restored Dimension TACR Assay: An Automated Platform for Measuring the Whole Blood Tacrolimus Concentration

BACKGROUND

Monitoring tacrolimus levels is essential for successful organ transplantation. The Dimension TACR (Siemens Healthcare Diagnostics, USA) is an automated platform used to measure tacrolimus concentrations. Recently, the manufacturer started shipping an assay reagent with improved functions. We evaluated the analytical performance of the improved Dimension TACR assay.

METHODS

The precision was evaluated according to the CLSI EP5-A2 guideline. Two levels of control materials were analyzed twice a day in duplicate for 20 days in the precision study. The linearity was evaluated using five levels of mixed calibrators based on the CLSI EP6-A guideline. A comparison study was conducted based on the CLSI EP9-A3 guideline using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The limit of blank (LoB), limit of detection (LoD), and limit of quantitation (LoQ) were evaluated using CLSI EP17-A2.

RESULTS

In the precision analyses, the within-run, between-run, and total coefficients of variation were 5.8%, 4.6%, and 8.1% for the low level control and 4.2%, 2.8%, and 5.9% for the high level, respectively. A linear range of 1.18-8.32 ng/mL was observed. In the comparison study, the correlation coefficient, slope, and intercept were 0.9768, 1.118, and -0.251, respectively. The results of the Dimension TACR assay were slightly higher than those of LC-MS/MS (mean bias 0.64 ng/mL). The LoB, LoD, and LoQ were 0.063 ng/mL, 0.408 ng/mL, and 1.15 ng/mL, respectively.

CONCLUSIONS

The Dimension TACR assay showed good precision and linearity. Although the results using the Dimension TACR assay were higher than those using mass spectrometry, the differences were acceptable clinically.