Laboratory validation and clinical performance of a saliva-based test for monkeypox virus

Improved diagnostic tests and accessibility are essential for controlling the outbreak of monkeypox. We describe a saliva-based polymerase chain reaction (PCR) assay for monkeypox virus, in vitro test performance, and clinical implementation of that assay in Los Angeles, San Francisco, and Palm Springs, CA. Finally, using prespecified search terms, we conducted a systematic rapid review of PubMed and Web of Science online databases of studies reporting the performance of oral pharyngeal or saliva-based tests for the monkeypox virus. The assay showed in silico inclusivity of 100% for 97 strains of monkeypox virus, with an analytic sensitivity of 250 copies/ml, and 100% agreement compared to known positive and negative specimens. Clinical testing identified 22 cases of monkeypox among 132 individuals (16.7%), of which 16 (72.7%) reported symptoms, 4 (18.2%) without a rash at the time of testing. Of an additional 18 patients with positive lesion tests, 16 (88.9%) had positive saliva tests. Our systematic review identified six studies; 100% of tests on oropharyngeal specimens from 23 patients agreed with the PCR test result of a lesion. Saliva-based PCR tests are potential tools for case identification, and further evaluation of the performance of such tests is warranted.