BK virus (BKV) infection and reactivation increase the risk of BKV-associated nephropathy and allograft failure in immune-compromised individuals;the condition could be managed by reducing immunosuppressive medication. Quantitative polymerase chain reaction (qPCR) screening for BKV has become the standard of care. The 1st World Health Organization International Standard for BKV DNA was introduced in 2016, facilitating standardizing and comparing various BKV qPCR assays. The Korean Association of External Quality Assessment Service (KEQAS) changed the reporting unit of BKV qPCR from log 10 copies/mL to log 10 IU/mL in 2024.This article shares our experience with calculating the conversion factor for copies-to-international units (IU) using standard materials. The conversion factors derived by Real-Q BK Virus Quantification Kit for plasma and urine were 0.48 and 0.19, respectively. The inconsistent performance of two identical nucleic acid extraction instruments was revealed, highlighting one of the various factors contributing to the variability of BKV quantification.We also considered the effects of changing the reporting unit on external quality assessment and standardization in general. Following the change, the KEQAS showed decreased interlaboratory variability. Switching the reporting unit to IU is expected to reduce inter-assay variability, providing each laboratory establishes and uses its conversion factor.

BK virus (BKV) infection and reactivation increase the risk of BKV-associated nephropathy and allograft failure in immune-compromised individuals;the condition could be managed by reducing immunosuppressive medication. Quantitative polymerase chain reaction (qPCR) screening for BKV has become the standard of care. The 1st World Health Organization International Standard for BKV DNA was introduced in 2016, facilitating standardizing and comparing various BKV qPCR assays. The Korean Association of External Quality Assessment Service (KEQAS) changed the reporting unit of BKV qPCR from log 10 copies/mL to log 10 IU/mL in 2024.This article shares our experience with calculating the conversion factor for copies-to-international units (IU) using standard materials. The conversion factors derived by Real-Q BK Virus Quantification Kit for plasma and urine were 0.48 and 0.19, respectively. The inconsistent performance of two identical nucleic acid extraction instruments was revealed, highlighting one of the various factors contributing to the variability of BKV quantification.We also considered the effects of changing the reporting unit on external quality assessment and standardization in general. Following the change, the KEQAS showed decreased interlaboratory variability. Switching the reporting unit to IU is expected to reduce inter-assay variability, providing each laboratory establishes and uses its conversion factor.

BK virus (BKV) infection and reactivation increase the risk of BKV-associated nephropathy and allograft failure in immune-compromised individuals;the condition could be managed by reducing immunosuppressive medication. Quantitative polymerase chain reaction (qPCR) screening for BKV has become the standard of care. The 1st World Health Organization International Standard for BKV DNA was introduced in 2016, facilitating standardizing and comparing various BKV qPCR assays. The Korean Association of External Quality Assessment Service (KEQAS) changed the reporting unit of BKV qPCR from log 10 copies/mL to log 10 IU/mL in 2024.This article shares our experience with calculating the conversion factor for copies-to-international units (IU) using standard materials. The conversion factors derived by Real-Q BK Virus Quantification Kit for plasma and urine were 0.48 and 0.19, respectively. The inconsistent performance of two identical nucleic acid extraction instruments was revealed, highlighting one of the various factors contributing to the variability of BKV quantification.We also considered the effects of changing the reporting unit on external quality assessment and standardization in general. Following the change, the KEQAS showed decreased interlaboratory variability. Switching the reporting unit to IU is expected to reduce inter-assay variability, providing each laboratory establishes and uses its conversion factor.

BK virus (BKV) infection and reactivation increase the risk of BKV-associated nephropathy and allograft failure in immune-compromised individuals;the condition could be managed by reducing immunosuppressive medication. Quantitative polymerase chain reaction (qPCR) screening for BKV has become the standard of care. The 1st World Health Organization International Standard for BKV DNA was introduced in 2016, facilitating standardizing and comparing various BKV qPCR assays. The Korean Association of External Quality Assessment Service (KEQAS) changed the reporting unit of BKV qPCR from log 10 copies/mL to log 10 IU/mL in 2024.This article shares our experience with calculating the conversion factor for copies-to-international units (IU) using standard materials. The conversion factors derived by Real-Q BK Virus Quantification Kit for plasma and urine were 0.48 and 0.19, respectively. The inconsistent performance of two identical nucleic acid extraction instruments was revealed, highlighting one of the various factors contributing to the variability of BKV quantification.We also considered the effects of changing the reporting unit on external quality assessment and standardization in general. Following the change, the KEQAS showed decreased interlaboratory variability. Switching the reporting unit to IU is expected to reduce inter-assay variability, providing each laboratory establishes and uses its conversion factor.

BK virus (BKV) infection and reactivation increase the risk of BKV-associated nephropathy and allograft failure in immune-compromised individuals;the condition could be managed by reducing immunosuppressive medication. Quantitative polymerase chain reaction (qPCR) screening for BKV has become the standard of care. The 1st World Health Organization International Standard for BKV DNA was introduced in 2016, facilitating standardizing and comparing various BKV qPCR assays. The Korean Association of External Quality Assessment Service (KEQAS) changed the reporting unit of BKV qPCR from log 10 copies/mL to log 10 IU/mL in 2024.This article shares our experience with calculating the conversion factor for copies-to-international units (IU) using standard materials. The conversion factors derived by Real-Q BK Virus Quantification Kit for plasma and urine were 0.48 and 0.19, respectively. The inconsistent performance of two identical nucleic acid extraction instruments was revealed, highlighting one of the various factors contributing to the variability of BKV quantification.We also considered the effects of changing the reporting unit on external quality assessment and standardization in general. Following the change, the KEQAS showed decreased interlaboratory variability. Switching the reporting unit to IU is expected to reduce inter-assay variability, providing each laboratory establishes and uses its conversion factor.

Maternally inherited diabetes and deafness (MIDD) is a rare mitochondrial disorder primarily resulting from m.3243A>G mutation. The clinical characteristics of MIDD exhibit significant heterogeneity. Our study aims to delineate these characteristics and determine the potential correlation with m.3243A>G heteroplasmy levels. This retrospective, descriptive study encompassed patients with confirmed m.3243A>G mutation and diabetes mellitus at Seoul National University Hospital. Our cohort comprises 40 patients with MIDD, with a mean age at study enrollment of 33.3±12.9 years and an average % of heteroplasmy of 30.0%± 14.6% in the peripheral blood. The most prevalent comorbidity was hearing loss (90%), followed by albuminuria (61%), seizure (38%), and stroke (33%). We observed a significant negative correlation between % of heteroplasmy and age at diabetes diagnosis. These clinical features can aid in the suspicion of MIDD and further consideration of genetic testing for m.3243A>G mutation.

Background: Inconclusive SARS-CoV-2 real-time reverse transcription-PCR (rRT-PCR) test results, which are positive for one or more target genes but not all, are problematic in clinical laboratories. In this study, we aimed to investigate the cause and clinical relevance of such inconclusive results. Methods: rRT-PCR was performed using the Allplex 2019-nCoV assay kit (Seegene Inc., Korea) targeting the following three genes: E, RdRp, and N. For all inconclusive test results reported from March to June 2020, the frequency per kit, lot number, specimen type, cycle threshold (Ct) and peak values of the amplification curves, positive target genes, and results of repeated or consecutive tests were analyzed. Results: A total of 43,268 tests were conducted, of which 93 (0.21%) were inconclusive—49 from 11 coronavirus disease 2019 (COVID-19) patients and 44 from non-COVID-19 patients.In COVID-19 patients, the results were inconclusive 11.9 ± 4.7 days after diagnosis and were negative 8.8 ± 5.5 days after the inconclusive results were reported. However, in nonCOVID-19 patients, they were all negative upon retest and 81.8% of them were identified to have yielded in 2 out of 8 lots. The most frequently positive target genes were N (55.4%) in COVID-19 and RdRp (61.2%) in non-COVID-19 patients, respectively. No difference was observed in the Ct or peak values of the amplification curves for inconclusive samples between COVID-19 and non-COVID-19 cases. Conclusion Inconclusive test results should be reported neither positive nor negative. Such results can be reported as inconclusive without retesting in COVID-19 patients; however, they should certainly be confirmed by a retest in non-COVID-19 patients or newly diagnosed cases.