A-297 Usefulness of Non-Skin Samples in the PCR Diagnosis of Monkeypox

Abstract Background During 2022, human mpox cases were reported in several European countries. Until November 2022, in Spain, 7404 cases were detected, most of them linked to sexual intercourse. In that context, fast identification of cases and sources of infection were essential for an optimal management. Polymerase chain reaction (PCR) was the preferred laboratory test. Our objective was to evaluate the usefulness of sera and nasopharyngeal samples for MPXV detection, and its application in contact studies without skin or mucosal injuries. Methods In the Hospital Clínico Universitario of Zaragoza (Spain), 106 samples from 50 patients, 38 male and 12 female, aged between 11 to 62 years, with skin lesions suspected MPXV infection were analysed. Samples were collected between May and September 2022 in inactivating universal viral transport medium (Biocomma). Samples were obtained between 1 and 19 days of evolution. To perform the real-time PCR, the VIASURE Monkeypox Virus Real Time PCR Detection Kit and the VIASURE 48—Real Time PCR System were used. Nucleic acid extraction was performed with the automated nucleic acid extraction system MagLEAD12gC using the MagDEA®Dx SV reagents. Results Table 1 shows the results expressed in Ct values. Skin, anogenital and serum samples were the most efficient for MPXV diagnosis. Nevertheless, these data are influenced by the sample collection date. Conclusion Real-time PCR was positive in samples from all locations in 71,4% of the infected patients. Respiratory samples (pharyngeal and nasopharyngeal) were the ones that showed the highest number of false negative results, whereas there was only one skin sample and one serum sample with a negative result. This study shows that sera samples can be used in the diagnosis of MPXV infection because of ease of collection, applicability to contacts without lesions and the option of serology testing for other STI agents (HBV, HCV, HIV, Treponema pallidum…). Table 1. Results of MPXV PCR of infected patients. Sample type No. Days of evolution (mean) Positive (%) Mean Ct Skin 14 2–9 (4.9) 13 (92.9) 26.0 Anogenital 23 1–7 (3.7) 22 (95.7) 23.7 Nasopharyngeal/Pharyngeal 15 2–10 (4.8) 11 (78.6) 31.3 Serum 18 1–9 (5.1) 17 (94.4) 34.6 Total 70 1–10 (4.5) 63 (90.0) 28.4