Diagnostic performance of the STANDARD™ Q Dengue DUO rapid diagnostic test in a resource-limited setting: a laboratory-based evaluation in the Republic of Niger

Dengue fever is an expanding public health threat in sub-Saharan Africa, yet access to laboratory-confirmed diagnosis remains severely constrained in resource-limited settings. Rapid diagnostic tests (RDTs) offer a practical alternative to molecular and serological diagnostic methods, but their performance must be validated in local epidemiological contexts before integration into national testing algorithms. We conducted a retrospective laboratory-based diagnostic accuracy study using 221 archived serum samples from suspected dengue patients admitted to public and private hospitals in Niamey between October and December 2023. The STANDARD™ Q Dengue DUO (SD Biosensor) was compared against qRT-PCR (NS1 reference) and ELISA IgM (IgM reference). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated with 95% Wilson score confidence intervals. Performance was stratified by viral load (Ct value) and time since symptom onset. Dengue infection was confirmed in 68/221 (30.8%) samples by qRT-PCR and 69/221 (31.2%) by IgM ELISA. For NS1 detection, the STANDARD™ Q demonstrated sensitivity of 79.4% (95% CI: 68.4–87.3%) and specificity of 85.5% (95% CI: 78.0–90.7%), with sensitivity increasing to 83.8% when combined with IgM. NS1 sensitivity was highest in samples with low and moderate viral load (Ct 20–30: 100%). NS1 sensitivity was 84.4% in the acute phase (≤ 7 days) versus 57.1% in the recovery phase (> 7 days). For IgM detection, sensitivity was 49.3% (95% CI: 38.2–60.4%) but specificity was 98.6% (95% CI: 95.0–99.6%), with IgM sensitivity rising to 100% in the recovery phase. The STANDARD™ Q Dengue DUO demonstrated adequate NS1 accuracy and high IgM specificity. Combined NS1 and IgM testing improves case detection across infection phases. Thus, we recommend this RDT as a first-line diagnostic tool in decentralized healthcare settings in Niger, although molecular testing remains essential for surveillance and serotyping purposes.