Evaluating the diagnostic accuracy of clinical judgement and rapid tests for leptospirosis in the Philippines: implications for public health management

Abstract

Background: Leptospirosis is endemic in the Philippines; however, its diagnosis remains challenging because of the lack of rapid and accurate diagnostic tools for detecting infection. Physicians must therefore resort to diagnosing leptospirosis through their clinical judgement, and this often results in under- or overestimation of cases. This study aimed to assess and compare the diagnostic accuracy of physicians’ clinical judgement and commercially available rapid test kits for leptospirosis against reference methods such as the microscopic agglutination test (MAT) and real-time polymerase chain reaction (qPCR) in the Philippines. Methods: A total of 127 serum samples were collected from patients suspected to have leptospirosis at three hospitals in the Philippines from August to December 2024. Rapid test kit results and final diagnoses were retrieved from the patients’ charts. MAT was performed on all the samples as a confirmatory method. Moreover, qPCR was performed on 30 randomly selected samples to increase the sensitivity of the reference standard. Sensitivity, specificity, positive and negative predictive values, and 95% confidence intervals were computed to determine the accuracy of both clinical judgement and rapid tests. Results: Among the 75 MAT-confirmed leptospirosis cases, approximately 24.0% were misdiagnosed as other febrile illnesses, such as dengue and typhoid fever, on the basis of clinical judgement, whereas 67.3% of the 52 MAT-negative patients were falsely diagnosed with leptospirosis. Overall, clinical judgement demonstrated high sensitivity (76.0%) but low specificity (33.7%), indicating possible overdiagnosis. The rapid test kits used in the laboratory exhibited significantly lower sensitivity (42.7%) but higher specificity (82.7%), suggesting a high probability of false-negative results. When qPCR was used in conjunction with these methods, relatively similar results were obtained. Conclusions: These findings highlight the diagnostic limitations in detecting leptospirosis in the Philippines, where laboratory testing options remain limited and inaccurate, resulting in physicians often relying on their clinical judgement. Misdiagnosis, whether through clinical judgement or rapid testing, could lead to inappropriate patient management, increased morbidity, and underestimation of leptospirosis incidence.