Evaluation of two commercial diagnostic methods for HHV-8 viral load assessment

Human Herpesvirus-8 (HHV-8) can cause Kaposi's sarcoma or B lymphoproliferative disorders such as multicentric Castleman disease. Patient follow-up is based on assessing the HHV-8 viral load, which is usually achieved using real-time Polymerase Chain Reaction (PCR). The HHV-8 Premix r-geneTM kit (BioMérieux®) was used by some laboratories in the past, but BioMérieux ceased the production and distribution of this kit in 2021-2022. Other kits need to be tested so that they can be used for diagnostic purposes. Here we evaluated two commercial kits: HHV8 ELITe MGB® Kit (ELITech) and Quanty HHV-8 (Clonit®) and compared them with the HHV-8 Premix r-gene kit. We used whole blood samples that had previously been tested with the HHV-8 Premix r-gene kit for diagnostic purposes. Forty-six samples (37 HHV-8-positive and 9 HHV-8-negative) were tested with the ELITe MGB® Kit and 37 (29 HHV-8-positive and 8 HHV-8-negative) with the Quanty HHV-8 kit. The different methods were compared using Bland-Altman and Passing-Bablok tests with Analyse-it software. Qualitative results were concordant except for one HHV-8 low-positive sample that was found to be negative by the ELITe MGB® Kit. The quantitative results were also concordant; both kits showed mean differences of 0.58 log10 copies/ml and 0.73 log10 copies/ml, respectively, compared to the Premix r-gene kit. Both the methods tested produced acceptable results and could be used for diagnostic purposes. It should be remembered that there is no international standard for HHV-8 quantification and that patients should always be followed using the same method.