RT-PCR Detects Low-Bacillary Leprosy More Accurately Than Slit-Skin Smears: Pilot Study
A recent cross-sectional pilot study published in the Indian Journal of Leprosy in February 2026 reveals a powerful new molecular screening tool for early leprosy detection. Boasting an impressive 86.4% sensitivity, this approach successfully identifies elusive low-bacillary cases that routinely evade conventional diagnostic methods.
Because classical evaluation strategies like the slit-skin smear (SSS) consistently present restricted sensitivity when assessing paucibacillary presentations, Dr. S. Mundada, along with affiliated researchers from the MGM Institute of Health Sciences, aimed to scientifically standardize an indigenous real-time polymerase chain reaction (RT-PCR) protocol for clinical use. Building upon prior research indicating that molecular testing is mostly confined to specialized labs, the authors addressed this urgent clinical gap by meticulously comparing their locally accessible RT-PCR assay’s diagnostic efficacy directly against established conventional methods to enhance early disease categorization.
Therefore, the prospective cross-sectional pilot study of 33 suspected leprosy patients compared the diagnostic accuracy of slit-skin smears and molecular testing against standard histopathology. The researchers evaluated key performance metrics like sensitivity and specificity, excluding patients with inadequate biopsy or DNA samples.
Key Clinical Findings of the Study Includes:
Histopathological Supremacy: The evaluation confirmed that traditional histopathology fundamentally retains its status as the supreme diagnostic gold standard, reliably yielding an outstanding 95.6% sensitivity and an absolute 100% specificity for accurate patient diagnosis.
Molecular Sensitivity: The researchers demonstrated that the novel RT-PCR screening yielded a significantly higher sensitivity of 86.4% alongside a 90.9% specificity, decisively eclipsing the disappointing 18.2% sensitivity recorded for routine standard smears.
Low-Load Efficacy: The investigation revealed that this genetic amplification strategy successfully detects traces of Mycobacterium leprae even in notoriously difficult paucibacillary cases where conventional microscopic examinations erroneously present as completely negative.
Comparative Accuracy: The analysis highlighted that the molecular test achieved an excellent area under the curve of 0.89 during ROC evaluations, vastly outperforming the modest 0.59 achieved by the traditional scraping methods.
The results suggest that while microscopic tissue examination retains maximum diagnostic accuracy, the newly standardized molecular testing offers a formidable 86.4% sensitivity that successfully uncovers pathogens in otherwise equivocal, low-bacillary patient profiles.
Thus, the study concludes that incorporating the advanced molecular testing algorithm as a complementary adjunct to established routine diagnostics could gently encourage healthcare professionals to confidently classify ambiguous presentations, subtly streamlining early intervention efforts without completely replacing traditional morphological evaluations.
Although constrained by a modest sample volume and a specialized single-center methodology, these preliminary insights mildly invite the initiation of broader, multicentric investigations to comfortably validate and seamlessly integrate this molecular adjunct into sweeping national disease control programs.
Reference
Mundada S, Patil YN, Tambekar M et al (2026). Comparative Study of Sensitivity and Specificity of RT-PCR, Histopathological Diagnosis and Slit Skin Smears in Detection of M leprae. Indian J Lepr. 98: 131-141.
