Single-Reaction Lassa RT-PCR Held Its Own Against Nigeria’s Dual-Target Standard
A single-reaction Lassa virus RT-PCR delivered near-identical performance to the dual-reaction reference method in a diagnostic accuracy study spanning two Nigerian laboratories, a result with direct implications for the way endemic settings manage suspected Lassa fever. Investigators evaluated PANDAA® LASV against the current standard RealStar® Lassa Virus RT-PCR Kit 2.0, which requires two separate reactions per sample to reduce the chance of missing a true infection. In a disease where delayed confirmation can complicate triage, isolation, and case management, trimming the assay from two reactions to one is not a trivial operational change.
The study used both retrospective and prospective plasma samples from patients who met the standard case definition for suspected Lassa fever. A total of 300 samples were included, with 200 collected retrospectively and 100 prospectively, across Abubakar Tafawa Balewa University Teaching Hospital in Bauchi and Federal Medical Centre in Owo. Against the reference assay, PANDAA LASV achieved sensitivity of 98.6% (138/140), specificity of 99.4% (155/156), and overall accuracy of 99.0% (293/296). The positive likelihood ratio reached 153.8, while the negative likelihood ratio was 0.01, values that place the assay in a strong diagnostic tier for ruling in and ruling out infection when used in the right clinical context.
One sentence captures the main operational message: the assay largely behaved like the standard test, but with half the reaction burden.
Discordant Results Clustered at the Edge of Detection
The few mismatches did not appear randomly distributed. Three confirmed discordant results occurred at high Ct values near the assay’s detection limits, the zone where low viral burden, specimen degradation, or stochastic amplification effects can expose the inherent fragility of any nucleic-acid test. In practical terms, those late Ct results are the cases most likely to create anxiety in the laboratory and the clinic, because a result hovering near the limit of detection can reflect a real infection with scant circulating RNA or a sample sitting on the boundary between positive and negative.
PANDAA Ct values tracked the reference assay closely. Correlation was significant for the L gene target (Spearman’s ρ = 0.80; p < 0.0001) and for the GPC target (ρ = 0.69; p < 0.0001). That concordance matters because Ct agreement is not just a statistical nicety; it suggests that the new assay is reading viral signal in a way that remains aligned with the established method rather than drifting unpredictably across lineages or sample ranges. In a virus as genetically diverse as Lassa, where intra- and inter-lineage variation complicates primer design, a stable correlation with the reference targets supports the biologic plausibility of the assay’s pan-lineage design.
The study also found no performance penalty across the two sites. Confidence intervals for sensitivity and specificity overlapped, and median Ct values did not differ between laboratories for any assay target. For decentralized testing programs, that consistency is as important as headline accuracy. A test that performs well in one expert laboratory but fractures in another has limited value in a real outbreak network.
Ct Patterns and Age Suggest a Viral Burden Signal Worth Watching
Median Ct values were significantly lower in patients aged 45 years or older (p = 0.008), indicating higher viral burden in that age group within this cohort. The study does not convert that association into an outcome analysis, and it does not claim prognostic meaning. Still, lower Ct values are generally consistent with more abundant viral RNA in plasma, which can reflect more intense systemic infection or later-stage disease biology in older patients. In endemic regions, that kind of age-linked viral burden difference can influence how clinicians interpret a borderline molecular result, especially when presentation is nonspecific and febrile illness overlaps with malaria, typhoid, and other common infections.
The diagnostic setting also gives weight to the assay architecture itself. PANDAA technology is designed to address sequence diversity by tolerating lineage variation that would otherwise weaken primer binding. For a hemorrhagic fever virus with meaningful genetic heterogeneity, that design choice is central. It is not enough for a PCR assay to work against one strain in a controlled panel; it has to keep working when real patient samples arrive from different lineages and different geographic pockets.
Laboratory Efficiency Could Shift Real-World Throughput
The strongest practical argument for PANDAA LASV lies in workflow simplification. Reducing the testing process from two PCR reactions per patient sample to one could lower labor demands, reagent use, and turnaround time without surrendering diagnostic performance. In settings where test volume, staffing, and supply chains all compete with one another, halving the number of reactions has consequences that extend beyond the bench. Faster confirmation can speed cohorting, guide supportive care, and help laboratories preserve scarce consumables during surges.
The study’s preprint status still leaves an important boundary around interpretation. Clinical validation against additional Lassa virus lineages remains the immediate priority, and that caution is justified. A pan-lineage assay has to earn that label across broader viral diversity, not only in the samples captured at two Nigerian sites. The manuscript also does not replace the need for ongoing quality control, especially around low-level positives near the assay’s limit of detection, where even a highly accurate test can be challenged by specimen quality and viral load.
Even so, the data support a clear conclusion: a single-reaction molecular assay can match the current dual-reaction standard closely enough to be taken seriously as a laboratory strategy for endemic Lassa fever diagnosis. The remaining work is not conceptual. It is validation across more lineages, more settings, and the full range of clinical presentations that define real-world suspicion of Lassa fever.