Diagnosis of Monkeypox infection: Validation of two diagnostic kits for viral detection using RT-PCR

Monkeypox virus, a zoonotic Orthopox DNA virus was rarely reported outside of African regions until April 2022. Since then, thousands of cases have been reported worldwide. In order to cope with the increasing need for laboratory diagnosis, the availability of reliable commercial PCR assays is of paramount importance. In this study we compared the diagnostic performance of two commercial real-time (RT)-PCR assays, the Novaplex™ MPXV Assay and the Bio-Speedy® Monkeypox Virus qPCR Kit, for the detection of Monkeypox virus (MPXV) DNA from 154 human samples. These assays were compared to a recently published in-house assay that included a general MPXV target (G2T) and a West African specific target (genericWA). All assays demonstrated 100% specificity. While sensitivity of the Novpalex assay was 100% the sensitivity of the other assays was lower; 94% for the Bio-speedy assay and G2R assay and 88% for the genericWA assay. The sensitivity differences between the methods manifested almost entirely in those pharyngeal samples in which the Ct values were high (≥35). The Novaplex™ MPXV Assay showed higher Ct values compared with the other methods with a median of 27.1 compared with the Bio-Speedy assay (median 15.8, p < 0.001), the G2R assay (median 23.5, p < 0.001) and the genericWA assay (median 23.6, p < 0.001). For all 4 methods, the Ct values were higher in samples taken from oropharynx compared with samples from rectal and pustule swabs.