Diagnostic Accuracy of Three Mpox Lateral Flow Assays for Antigen Detection in the Democratic Republic of Congo and the United Kingdom

Abstract

Background: The ongoing outbreaks of mpox, the disease caused by monkeypox virus (MPXV), highlight the urgent need for a rapid and low-cost MPXV diagnostic test to accurately detect and control mpox disease.

Methods: We estimated the clinical diagnostic performance of three MPXV antigen detection rapid diagnostic tests (Ag–RDT) using skin lesion swabs (SS) and upper–respiratory tract swabs (URS) from 68 participants in the Democratic Republic of the Congo (DRC) and from 16 in the United Kingdom (UK). The limit of detection (LOD) was evaluated using viral culture of the MPXV of the IIb lineage.

Findings: The specificity of the three Ag–RDT was high (100%) across all sample types. The sensitivity was estimated between 0.00% (95% CI, 0·0–20·6%) to 15·79% (95% CI, 5·52–37·57%) using SS depending on the Ag-RDT brands and country and 0.00% (95% CI, 0·0–20·6%) using URS. The LOD of all Ag–RDT was 1·0x 104 pfu/ml fulling the analytical sensitivity in the WHO target product profile (TPP).

Interpretation: None of the three Ag–RDT reached the target clinical sensitivity and thus we do not recommend these as diagnostic or screening tool for suspected mpox cases. Marked improvement in sensitivity are needed for these Ag–RDT prior adoption. The recommended analytical LOD in the WHO TPP does not align with the desired clinical sensitivity. There remains an urgent need for accurate rapid Ag-RDTs for mpox diagnosis.

Funding: This work was funded as part of FIND’s work as co-convener of the diagnostics pillar of the Pandemic Threats Programme who received funds from the German (Federal Ministry of Economic Cooperation and Development) and Canadian Government. ISARIC4C was funded from the National Institute for Health Research (NIHR) (award CO-CIN-01), the UK Medical Research Council (grant MC_PC_19059), the NIHR for Health Research Health Protection Research Unit (HPRU) in Emerging and Zoonotic Infections (in partnership with the University of Liverpool, the United Kingdom Health Security Agency (UKHSA), LSTM and the University of Oxford) (NIHR award 200907), the Welcome Trust and Department for International Development (215091/Z/18/Z), Bill and Melinda Gates Foundation (OPP1209135), and the Liverpool Experimental Cancer Medicine Centre (Grant Reference: C18616/A25153). The FALCON study was funded by the NIHR, Asthma United Kingdom, and the British Lung Foundation.

Declaration of Interest: The authors report no conflicts of interest. The opinions expressed here are solely those of the authors and may not represent the views of the funding organisations.

Ethical Approval: In the DRC ehical approval was obtained by the DRC's National Ethics and Health Committee (Comité National d'Ethique et de la Santé, CNES), reference 452/CNES/BN/PMMF/2023. In the UK patients were consented under the WHO ISARIC Clinical Characterisation Collaboration Protocol for severe emerging infections (ISRCTN66726260) ethical approval was obtained from the National Research Ethics Service and the Health Research Authority (IRAS ID:126600, REC 13/SC/0149). Mpox negative controls were collected under the Facilitating Accelerated Clinical Validation of Novel diagnostics for COVID–19 (FALCON), and ethical approval was obtained from the National Research Ethics Service and the Health Research Authority (IRAS ID:28422, REC: 121 20/WA/0169).

Keywords: mpox, monkeypox virus (MPXV), rapid diagnostic test (RDT), Point-of-Care (POC), diagnostics, Orthopoxvirus, lateral flow test (LFA)