Identification of Mutations in the Thyroxine-Binding Globulin (TBG) Gene in Patients with TBG Deficiency in Korea

Background@#Thyroxine-binding globulin (TBG) is a major transporter protein for thyroid hormones. The serpin family A member 7 (SERPINA7) gene codes for TBG, and mutations of the SERPINA7 gene result in TBG deficiency. Although more than 40 mutations have been reported in several countries, only a few studies of TBG deficiency and SERPINA7 gene mutation have been performed in Korea. The aim of this study is to review the clinical presentations and laboratory findings of patients with TBG deficiency and to investigate the types of SERPINA7 gene mutation. @*Methods@#Five unrelated Korean adults with TBG deficiency attending endocrinology clinic underwent SERPINA7 gene sequencing. Four patients harbored a SERPINA7 gene mutation. Serum thyroid hormones, anti-microsomal antibodies, and TBG were measured. Genomic DNA was extracted from whole blood. All exons and intron-exon boundaries of the TBG gene were amplified and sequencing was performed. @*Results@#Two patients were heterozygous females, and the other two were hemizygous males. One heterozygous female had coexisting hypothyroidism. The other heterozygous female was erroneously prescribed levothyroxine at a local clinic. One hemizygous male harbored a novel mutation, p.Phe269Cysfs*18, which caused TBG partial deficiency. Three patients had the p.Leu372Phefs*23 mutation, which is known as TBG-complete deficiency Japan (TBG-CDJ) and was also presented in previous mutation analyses in Korea. @*Conclusion@#This study presents four patients diagnosed with TBG deficiency and provides the results of SERPINA7 gene sequencing. One novel mutation, p.Phe269Cysfs*18, causing TBD-partial deficiency and three cases of TBG-CDJ were demonstrated. It is necessary to identify TBG deficiency to prevent improper treatment. Also, sequencing of the SERPINA7 gene would provide valuable information about the TBG variants in Korea.

Immunosuppressive Drug Measurement by Liquid Chromatography Coupled to Tandem Mass Spectrometry: Interlaboratory Comparison in the Korean Clinical Laboratories

Background@#Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is increasingly used for immunosuppressive drug tests. However, most LC-MS/MS tests are laboratory-developed and their agreement is unknown in different Korean laboratories.This interlaboratory comparison study evaluated test reproducibility and identified potential error sources. @*Methods@#Test samples containing three concentrations of tacrolimus, sirolimus, everolimus, cyclosporine, and mycophenolic acid were prepared by pooling surplus samples from patients undergoing routine therapeutic drug monitoring and tested in duplicate in the participating 10 clinical laboratories. Reconstitution and storage experiments were conducted for the commonly used commercial calibrator set. The robust estimators of reproducibility parameters were calculated. Spearman’s rank correlation coefficient (rho, ρ) was used to evaluate the correlation between drugs. Multiple linear regression was used to determine whether the experimental conditions alter the calibration curves. @*Results@#The reproducibility coefficient of variation exceeded 10% only for sirolimus concentrations 1 and 2 (10.8% and 12.5%, respectively) and everolimus concentrations 1 and 2 (12.3% and 11.4%, respectively). The percent difference values showed weak correlations between sirolimus and everolimus (ρ = 0.334, P = 0.175). The everolimus calibration curve slope was significantly altered after reconstitution following prolonged 5°C storage (P = 0.015 for 14 days; P = 0.025 for 28 days); the expected differences at 6 ng/mL were 0.598% for 14 days and 0.384% for 28 days. @*Conclusions@#LC-MS/MS test reproducibility for immunosuppressive drugs seems to be good in the Korean clinical laboratories. Continuous efforts are required to achieve test standardization and harmonization, especially for sirolimus and everolimus.

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.

Comparison of Three Blood Collection Tubes for 35 Biochemical Analytes: The Becton Dickinson Barricor Tube, Serum Separating Tube, and Plasma Separating Tube

The Barricor tube (Becton Dickinson [BD], Sunnyvale, CA, USA) was recently developed to mechanically separate plasma by increasing the centrifugation rate. We compared the Barricor tube with existing serum- and plasma-based tubes based on 35 biochemical analytes and preanalytical turnaround time (TAT). Blood samples were collected from 30 healthy volunteers in a Barricor tube, serum separating tube (SST, Vacutainer SST II Tube 8.5 mL, #368972; BD), or plasma separating tube (PST, Vacutainer PST Tube 8.0 mL, #367964; BD) in random order. Next, 27 chemistry analytes, six immunochemistry analytes, and two cardiac markers were compared using Passing-Bablok regression and the Bland-Altman method. Preanalytical TAT was measured for each tube.The Barricor tube exhibited bias exceeding the desirable limit for nine and four analytes compared with the SST and PST, respectively. The Barricor tube lactate dehydrogenase value showed a bias of -10.29% and -9.86% compared with that of the SST and PST, respectively. The preanalytical TAT of Barricor tube was 8.8 minutes, which was the shortest among the three tubes. The clinical performance of the Barricor tube was equivalent to that of the SST and PST for most analytes, with an apparent advantage in preanalytical TAT. When using the Barricor tube, the reference range needs to be changed for some analytes that exceed the desirable bias limit.

Recommendations for Liquid Chromatography-Mass Spectrometry in the Clinical Laboratory: Part III. Quality Assurance

The use of liquid chromatography-tandem mass spectrometry (LC-MS/MS) in clinical laboratories is increasing and is likely to expand into even more clinical venues in the future. Mass spectrometry is the standard method for analyte identification in the clinical chemistry field; however, differences in mass spectrometry protocols and handling affect the accuracy and reliability of these tests and prevent direct comparisons of results between laboratories. For example, the results of laboratories using LC-MS/MS methods are less likely to be reproducible than those of laboratories using conventional, automated methods. This is due to inadequate handling of the equipment and/or poor quality control after the implementation of the method, which may result in unnecessary medical expenditures or even adverse outcomes for the patients. Unfortunately, guidelines to monitor the accuracy of LC-MS/MS-based clinical tests are still lacking. In general, the quality control methods used in conventional clinical tests could also be applied to LC-MS/MS. However, additional quality control methods specific to LC-MS/MS techniques must be continuously employed to maintain the same quality level achieved during method development and verification. This report is intended to help clinical laboratories that operate LC-MS/MS improve the accuracy and reliability of their testing by providing guidance for quality assurance and improvement, based on a collection of existing guidelines and expert opinions from the literature.

Performance Evaluation of Serum IgD Quantification by the SPAPLUS Turbidimetric Analyzer and Determination of a Reference Interval of IgD in the Korean Population

Background@#IgD is an immunoglobulin isotype that accounts for 100 mg/L. The established upper limit of the reference interval was 53.6 mg/L. @*Conclusions@#The SPAPLUS shows good analytical performance for serum IgD quantification.

Therapeutic Drug Level Monitoring of Teicoplanin in Korean Pediatric Patients with Normal versus Impaired Renal Function

Background@#Teicoplanin is used to treat serious gram-positive infections. Optimal teicoplanin trough levels are considered to be ≥ 10 μg/mL. Despite its wide use in various clinical settings, data on teicoplanin trough level in pediatric patients are limited. Therefore, the aim of this study was to investigate the therapeutic drug level monitoring of teicoplanin in Korean pediatric patients, including those with impaired renal function. @*Methods@#A retrospective study was performed in pediatric patients (age ≤ 18 years old) who received teicoplanin from September 2014 to April 2018. The regimen included a loading dose of 10 mg/kg/dose at 12 hours' interval three times in a row, and a maintenance dose of 10 mg/kg/dose commenced at 24 hours of interval after the loading dose, with a maximum of 400 mg/dose, respectively. The first therapeutic drug levels were measured. Distribution and characteristics of trough levels in patients with decreased renal function and those with bacteremia were also assessed. @*Results@#A total of 187 trough levels were collected from 143 patients. Hematologic and oncologic diseases were the most common underlying diseases (83.2%, n = 119). One hundred eighty trough levels were first measured, and their median value was 16.2 μg/mL (range, 2.3–100 μg/mL) and the median interval between initial teicoplanin injection and 1st trough level was 96.5 hours (range 47.6–179.3 hours). Lower steady-state levels were observed in younger age group (median, 13.5 vs. 18.0 μg/mL, P = 0.038). Median trough levels were higher in patients with decreased renal functions (P < 0.001). In addition, among eight with gram-positive bacteremia, seven of them had a favorable outcome. @*Conclusion@#This study provides additive information on trough level monitoring of teicoplanin in children with impaired renal function and treatment effect in patients with gram-positive bacteremia. Careful monitoring for steady state trough levels of teicoplanin is warranted.

Vancomycin and Aminoglycoside Antibiotic Drug Concentration Measurement: Current Status in Clinical Laboratories in Korea

Background@#Therapeutic drug monitoring (TDM) is clinically recommended for vancomycin and aminoglycoside antibiotics owing to their narrow therapeutic range and nephrotoxicity at high concentrations in the blood. This study was conducted to investigate the current status of TDM of vancomycin and aminoglycosides in Korean clinical laboratories. @*Methods@#Ten organizations participated in this survey. Vancomycin, amikacin, gentamicin, and tobramycin were prepared in three samples of five or six different concentrations. Data from each institution were calculated for the mean, standard deviation, within-day, between-day, and within-laboratory precision. The results from each institution were compared in various ways. @*Results@#Six instruments from three manufacturers were used. Samples with the lowest drug concentration were reported as below the lower limit of quantitation in most laboratories. Coefficients of variation for within-laboratory values ranged from 1.1% to 10.9% for vancomycin, 0.8% to 18.2% for amikacin, 1.2% to 7.8% for gentamicin, and 1.3% to 6.1% for tobramycin. Based on the overall results of the participants, only one institution’s vancomycin samples standard deviation index exceeded 3, with all other values below 2. The College of American Pathologist criteria were met by all institutions; however, measurement of vancomycin in one laboratory and of gentamycin in three laboratories failed to meet the Royal College of Pathologists of Australasia acceptance criteria. @*Conclusions@#Although the precision of the antibiotic test in individual institutions was excellent, there was a difference in the measured values between laboratories. Harmonization of antibiotic TDM is needed to reduce inconsistencies in results.

Vancomycin and Aminoglycoside Antibiotic Drug Concentration Measurement: Current Status in Clinical Laboratories in Korea

Background@#Therapeutic drug monitoring (TDM) is clinically recommended for vancomycin and aminoglycoside antibiotics owing to their narrow therapeutic range and nephrotoxicity at high concentrations in the blood. This study was conducted to investigate the current status of TDM of vancomycin and aminoglycosides in Korean clinical laboratories. @*Methods@#Ten organizations participated in this survey. Vancomycin, amikacin, gentamicin, and tobramycin were prepared in three samples of five or six different concentrations. Data from each institution were calculated for the mean, standard deviation, within-day, between-day, and within-laboratory precision. The results from each institution were compared in various ways. @*Results@#Six instruments from three manufacturers were used. Samples with the lowest drug concentration were reported as below the lower limit of quantitation in most laboratories. Coefficients of variation for within-laboratory values ranged from 1.1% to 10.9% for vancomycin, 0.8% to 18.2% for amikacin, 1.2% to 7.8% for gentamicin, and 1.3% to 6.1% for tobramycin. Based on the overall results of the participants, only one institution’s vancomycin samples standard deviation index exceeded 3, with all other values below 2. The College of American Pathologist criteria were met by all institutions; however, measurement of vancomycin in one laboratory and of gentamycin in three laboratories failed to meet the Royal College of Pathologists of Australasia acceptance criteria. @*Conclusions@#Although the precision of the antibiotic test in individual institutions was excellent, there was a difference in the measured values between laboratories. Harmonization of antibiotic TDM is needed to reduce inconsistencies in results.

Recommendations for the Use of Liquid Chromatography-Mass Spectrometry in the Clinical Laboratory: Part I. Implementation and Management

Performance Evaluation and Clinical Usefulness of α-fetoprotein Test Measured on Sysmex HISCL-5000

Comparison of Serum Creatinine Measurements among Roche Modular D, Cobas 8000 c702, and Beckman Coulter AU5800, by Jaffe and Enzymatic Methods

0.99, slope: 0.965 and 0.955). When Modular D and Cobas 8000c 702 were compared, the slope and y-intercept were 0.9928 (95% confidence interval [CI]: 0.9802 to 1.000) and -0.0156 (95% CI: −0.0200 to −0.0054), respectively. The slope and y-intercept were 0.9811 (95% CI: 0.9570 to 0.9951) and -0.0484 (95% CI: −0.0638 to −0.0297) when Modular D and Au5800 were compared. Serum Cr measured by Cobas 8000 c702 and AU5800 using the Jaffe method were 3.2% and 6.9% lower than the values measured by Modular D, respectively. Both Modular D and Cobas 8000 c702 showed acceptable accuracies.CONCLUSIONS: Serum Cr measurements using Cobas 8000 c702 and AU5800 were comparable to those measured by Modular D, and showed satisfactory precision and linearity; thus, these techniques could be useful for clinical laboratories.

Analyses of the Proficiency Testing Program and the Performance of Qualitative Reagents for Rheumatoid Factor / 임상검사와정도관리

BACKGROUND: Rheumatoid factor (RF) is used as one of the diagnostic criteria for rheumatoid arthritis. The purpose of this study was to evaluate qualitative RF reagents used in clinical laboratories in Korea, and to provide basic data that can be used as a reference to improve the quality of RF testing. METHODS: We reviewed the proficiency testing results for RF from the Korean Association of External Quality Assessment Service (KEQAS) and College of American Pathologists. Moreover, we evaluated five commercially available RF qualitative reagents, including LabSlide RF (IVD Lab Co., Korea), ASAN RA Latex Reagents (Asan Pharmaceuticals Co., Korea), RaPET RF (Stanbio Laboratory, USA), RF Latex Test (Pulse Scientific Inc., Canada), and RF-100 (Teco Diagnostics, USA). Commercially available quality control materials, calibrators, and pooled sera were used in this study. The consistency of qualitative reagents and Kappa statistics were calculated based on the quantitative values of the quality control materials and the mixed sera. RESULTS: Up to 51.5% of high concentration samples were reported as negative in KEQAS. RF qualitative reagent test results were not consistent among reagent types. The consistency of the qualitative and quantitative test results was between 51% and 100%, and the kappa statistics varied depending on the reagent manufacturer. CONCLUSIONS: Measurement of RF qualitative reagents used in domestic clinical laboratories was not consistent with the quantitative values, and hence it is necessary to improve the consistency and verify the adequacy of the cut-off value.

Thyroid Hormone Resistance in a Preterm Infant with a Novel THRB Mutation

Resistance to thyroid hormone (RTH) is a condition caused by a mutation in the thyroid hormone receptor gene. It is rarely reported in individuals with no family history of RTH or in premature infants, and its clinical presentation varies. In our case, a premature infant with no family history of thyroid diseases had a thyroid stimulating hormone level of 85.0 µIU/mL and free thyroxine level of 1.64 ng/dL on a thyroid function test. The patient also presented with clinical signs of hypothyroidism, including difficulties in feeding and weight gain. The patient was treated with levothyroxine; however, only free thyroxine and triiodothyronine levels increased without a decrease in thyroid-stimulating hormone levels. Taken together with thyroid gland hypertrophy observed on a previous ultrasound examination, RTH was suspected and the diagnosis was eventually made based on a genetic test. A de novo mutation in the thyroid hormone receptor β gene in the infant was found that has not been previously reported. Other symptoms included tachycardia and pulmonary hypertension, but gradual improvement in the symptoms was observed after liothyronine administration. This report describes a case involving a premature infant with RTH and a de novo mutation, with no family history of thyroid disease.

A Questionnaire Survey on General Status and Opinions about Clinical Mass Spectrometric Analysis in Korea (2018)

The Clinical Mass Spectrometry Research Committee (CMSRC), in affiliation with the Korean Society of Clinical Chemistry (KSCC), conducted a questionnaire survey on opinions about the general status of clinical mass spectrometric analysis in Korea. As a result, we understand that this field has passed through the introductory stage and is settled as a field of clinical laboratory testing in Korea, with the number of new laboratories performing mass spectrometric analysis being low. In spite of the many difficulties in introducing and operating clinical mass spectrometric analysis, there is a strong interest in this field, and even though further expansion is expected, there are still many issues to be resolved. In the future, it will be necessary to make concrete and thorough efforts to further develop the laboratory tests using clinical mass spectrometric analysis in Korea, centering on the CMSRC affiliated with the KSCC.

Clinical and molecular characterization of Korean children with infantile and late-onset Pompe disease: 10 years of experience with enzyme replacement therapy at a single center / 소아과

PURPOSE: Pompe disease (PD) is an autosomal recessive disorder caused by a deficiency of acid alpha-glucosidase resulting from pathogenic GAA variants. This study describes the clinical features, genotypes, changes before and after enzyme replacement therapy (ERT), and long-term outcomes in patients with infantile-onset PD (IOPD) and late-onset PD (LOPD) at a tertiary medical center. METHODS: The medical records of 5 Korean patients (2 male, 3 female patients) diagnosed with PD between 2002 and 2013 at Samsung Medical Center in Seoul, Republic of Korea were retrospectively reviewed for data, including clinical and genetic characteristics at diagnosis and clinical course after ERT. RESULTS: Common initial symptoms included hypotonia, cyanosis, and tachycardia in patients with IOPD and limb girdle weakness in patients with LOPD. Electrocardiography at diagnosis revealed hypertrophic cardiomyopathy in all patients with IOPD who showed a stable disease course during a median follow-up period of 10 years. Patients with LOPD showed improved hepatomegaly and liver transaminase level after ERT. CONCLUSION: As ERT is effective for treatment of PD, early identification of this disease is very important. Thus, patients with IOPD should be considered candidates for clinical trials of new drugs in the future.

Clinical Utility and Cross-Reactivity of Insulin and C-Peptide Assays by the Lumipulse G1200 System

BACKGROUND: Measurement of insulin and C-peptide concentrations is important for deciding whether insulin treatment is required in diabetic patients. We aimed to investigate the analytical performance of insulin and C-peptide assays using the Lumipulse G1200 system (Fujirebio Inc., Tokyo, Japan). METHODS: We examined the precision, linearity, and cross-reactivity of insulin and C-peptide using five insulin analogues and purified proinsulin. A method comparison was conducted between the Lumipulse G1200 and Roche E170 (Roche Diagnostics, Mannheim, Germany) systems in 200 diabetic patients on insulin treatment. Reference intervals for insulin and C-peptide concentrations were determined in 279 healthy individuals. RESULTS: For insulin and C-peptide assays, within-laboratory precision (% CV) was 3.78–4.14 and 2.89–3.35%, respectively. The linearity of the insulin assay in the range of 0–2,778 pmol/L was R2=0.9997, and that of the C-peptide assay in the range of 0–10 nmol/L was R2=0.9996. The correlation coefficient (r) between the Roche E170 and Lumipulse G1200 results was 0.943 (P < 0.001) for insulin and 0.996 (P < 0.001) for C-peptide. The mean differences in insulin and C-peptide between Lumipulse G1200 and the Roche E170 were 19.4 pmol/L and 0.2 nmol/L, respectively. None of the insulin analogues or proinsulin showed significant cross-reactivity with the Lumipulse G1200. Reference intervals of insulin and C-peptide were 7.64–70.14 pmol/L and 0.17–0.85 nmol/L, respectively. CONCLUSIONS: Insulin and C-peptide tests on the Lumipulse G1200 show adequate analytical performance and are expected to be acceptable for use in clinical areas.

A Case of Glycogen Storage Disease IV with Rare Homozygous Mutations in the Glycogen Branching Enzyme Gene / 대한소아소화기영양학회지

Glycogen storage disease (GSD) IV is a rare autosomal recessive inherited disorder caused by mutations in the gene coding for glycogen branching enzyme leading to progressive liver disease. GSD IV is associated with mutations in GBE1, which encodes the glycogen branching enzyme. We report a case of GSD IV with rare homozygous mutations in the GBE1 gene (c.791G>A (p.Gly264Glu), which was successfully treated by liver transplantation.

Annual Report on the External Quality Assessment Scheme for Hormones in Korea (2017)

In 2017, the Korean Association of External Quality Assessment Service developed a hormone proficiency testing program that comprised 11 test items for hormone I and four test items for hormone II. This program was conducted twice a year using three-level control materials. Data and results of each test item were analyzed by the respective institutions according to the test instruments. The report was prepared by dividing it into a common report that showed the characteristics of the overall participating institutions and an organization-specific report that showed the assessment data of individual institutions. The following statistical data were presented: the number of participating institutions per group, mean, standard deviation, coefficient of variation, median, minimum value, and maximum value. The individual report was composed of a table, histogram, and Levey-Jennings chart showing the statistics for each test item. The results of the assessment of each institution and the statistical data for each classification are presented in a table, and a standard deviation index was provided for both the company classification and classification by instruments. Although the total number of participating institutions and distribution of test instruments were not significantly different from the previous year, the number of participating institutions varied by test item. The coefficient of variation tended to be relatively high for each test item because the concentration of quality control materials was low and the number of participating institutions was small. I believe that these statistical analysis data are useful for analyzing external quality control results of the institutions and selecting an immunoassay test instrument for hormones.