Lab Med Qual Assur.  2024 Dec;46(4):225-229. 10.15263/jlmqa.2024.46.4.225.

Calculation of Conversion Factors Using the 1st World Health Organization International Standard for BK Virus DNA Quantification

• Lee H
• Park G

• KMID: 2563494
• DOI: http://doi.org/10.15263/jlmqa.2024.46.4.225

Abstract

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.

Keyword

BK virus; Standardization; International Standard; Conversion factor; International unit; Quantitative polymerase chain reaction