When Diagnosis Meets Reality: Operational Performance of Routine Malaria Diagnostics Against Molecular Evidence in Southwestern Saudi Arabia.

BACKGROUND

Saudi Arabia has reported no indigenous malaria since 2021 and is in the prevention-of-reintroduction phase, with residual and imported infections concentrated in Jazan and Aseer. At this stage, each reported case triggers programmatic action, yet the operational accuracy of routine facility diagnostics has not been measured in this setting.

OBJECTIVE

To evaluate the operational accuracy of facility-performed routine light microscopy (RLM) and two Pf/PAN rapid diagnostic tests (RDTs) against species-specific nested PCR.

METHODS

Retrospective diagnostic accuracy study on consecutively archived specimens. Of 118 archived EDTA samples from febrile patients tested for suspected malaria at hospitals in nine governorates of southwestern Saudi Arabia during January-December 2023, 106 were eligible (12 were excluded). Index tests were performed by facility staff during routine care; nested PCR was later performed blinded. Accuracy was assessed against nested PCR and, in a sensitivity analysis, a composite reference (RLM or PCR positive).

RESULTS

Nested PCR detected Plasmodium in 81/106 samples (76.4%; 95% CI 67.2-84.0), all single-species (P. falciparum 56/81; P. vivax 25/81). RLM was positive in 98/106 (92.5%), CareStart in 106/106 (100%), QuickProfile in 100/106 (94.3%). RLM called 29/98 positives mixed (29.6%) versus 0/81 by PCR (Fisher's exact, p < 0.001). Against PCR, RLM sensitivity was 97.5% (91.3-99.6) and specificity 24.0% (10.2-45.5); CareStart specificity 0% (0-13.9), QuickProfile 20.0% (8.1-39.8). PCR confirmation increased with reported parasitemia, from 12/23 (52.2%) at 10-90 parasites/μL to 22/24 (91.7%) at 1000-10,000 parasites/μL (Cochran-Armitage, p < 0.001).

CONCLUSION

In the selected clinically suspected cases, routine diagnostics returned more positives, and far more mixed infections, than nested PCR; both routine false positives and reduced PCR sensitivity in archived material plausibly contribute. Findings should not be extrapolated beyond this population. Strengthened microscopy training, RDT quality assurance, and evaluation of molecular confirmation may support case classification during the prevention-of-reintroduction phase.