Hepatology (Baltimore, Md.) 2016 8 17() doi 10.1002/hep.28772
Infection by the hepatitis Delta virus (HDV), a satellite of the hepatitis B virus (HBV), increases viral liver disease severity. Its diagnosis is thus vital for HBV-infected patients. HDV-RNA load (HDVL) should be assessed and monitored in plasma using real time RT-PCR assays. Taking advantage of the recently-developed WHO HDV international standard (WHO-HDV-IS), the first international external quality control for HDVL quantification was performed. Two panels of samples were sent to 28 laboratories in 17 countries worldwide. Panel A comprised 20 clinical samples of various genotypes (1, 2 and 5 to 8) and viral loads, including two negative controls. Panel B, composed of dilutions of the WHO-HDV-IS, allowed the conversion of results from copies/mL into international units (IU)/mL for HDVL standardization and interlaboratory comparisons. Comprehensive analysis revealed a very high heterogeneity of assay characteristics, including their technical steps and technologies. Thirteen labs (46.3%) properly quantified all 18 positive samples; 16 (57.1%) failed to detect 1 to up to 10 samples, and several others underestimated (≥3 log IU/mL) HDVL of African genotype strains (1 and 5 to 8). Discrepancies were mainly due to either primer or probe mismatches related to the high genetic variability of HDV and possibly to the complex secondary structure of the target genomic RNA. The labs were grouped in four clusters by the statistical analysis of their performances. The best cluster comprised the 11 labs that obtained the expected HDVL values, including three that otherwise failed to quantify one or two samples.
The results of this international quality control study underline the urgent need to improve methods used to monitor HDV viremia and will be instrumental in achieving that goal. This article is protected by copyright. All rights reserved.