A-301 Analytical and Clinical Performance of the Molecular Method for Monkeypox Virus Detection
Authors: Silva J D , Zauli D A 
Published: September 2023

Abstract

Background
Monkeypox (MPX) is a zoonose caused by the Monkeypox virus (MPXV) belonging to the Orthopoxvirus genus of the Poxviridae family. Currently, MPXV is responsible for more than 84 000 infections worldwide, resulting in major social impacts. Although the reservoir is unknown, the main hosts are small rodents, typical of the tropical forests of West and Central Africa. The transmission occurs by interactions of infected animal-to-person (direct contact with the blood, bodily fluids, or cutaneous/mucosal lesions) and person-to-person (close contact with respiratory secretions, skin lesions, or recently contaminated objects). After infection, there is an incubation period of approximately 1–2 weeks (asymptomatic and non-transmissible), followed by the development of skin rashes over the body, lymphadenopathy, and systemic symptoms (fever, malaise, headache, myalgia, and fatigue). The rapid and accurate diagnosis of MPX is extremely important for combating the virus and also for epidemiological tracking. In this sense, molecular methods have been shown essential for the accurate detection and characterization of MPXV. Therefore, this study aims to describe the analytical and clinical validation of real-time polymerase chain reaction (qPCR) assay for MPXV detection.

Methods
The qPCR assay used in this validation was based on recommendations published by the Center for Disease Control and Prevention (CDC). The primer/probe sequence was commercially acquired and included the analysis of a MPXV-specific genomic region (CADT ID APNKYAD; Thermo Fisher, USA). Assay performance was evaluated using inactivated viral isolates and positive samples with known MPXV positive results. The analysis parameters included: (i) assay verification (performance evaluation of probes and reagents); (ii) Analytical sensitivity; (iii) Limit of detection (LOD); (iv) Analytical specificity (interference study with Herpes simplex virus and Varicella-Zoster virus); and (v) clinical validation (10 positive skin rashes samples for the MPXV).

Results
The assay demonstrated good performance visualized by the qPCR amplification curves (low cycle threshold (Ct) value and high fluorescence level) with an efficiency &gt;92%. Analytical sensitivity and LOD tests were 100% and 50 copies/µL, respectively, considering a 95% confidence interval. The regression equations obtained show satisfactory reaction conditions with a positive correlation between the variables (coefficient of determination (r2) = 0.99). The assays indicated no cross-reactions with closely related viruses, demonstrating 100% of specificity. Finally, clinical validation showed 100% agreement with the expected results for all samples evaluated.

Conclusion
qPCR can play an important role in the rapid and accurate diagnosis of several viruses. The analytical and clinical validation provided data indicating high sensitivity and specificity for MPX detection. This study allowed the implementation of a sensitive, specific, and accurate molecular test for viral agent identification and allow prompt surveillance action by health such as epidemiological monitoring and control measures of these infections.