SYBR Green qPCR on Noninvasive Swabs Matches Biopsy Accuracy for Leishmaniasis Diagnosis
In a study of 91 patients from a Leishmania braziliensis-endemic area, SYBR Green-based qPCR on swab samples achieved 87.9% diagnostic accuracy with 100% specificity, comparable to biopsy-based testing. The noninvasive swab approach outperformed conventional parasitological methods and offers a practical alternative for resource-limited settings where mucosal leishmaniasis poses diagnostic challenges due to low parasite burden. For laboratories in endemic regions, this validated swab-plus-qPCR workflow can reduce the need for invasive tissue sampling.
The original study
Field Validation of SYBR Green- and TaqMan-Based Real-Time PCR Using Biopsy and Swab Samples To Diagnose American Tegumentary Leishmaniasis in an Area Where Leishmania (Viannia) braziliensis Is Endemic.
- Authors
- Gomes CM, Cesetti MV, de Paula NA, Vernal S, Gupta G, Sampaio RN, et al.
- Journal
- Journal of clinical microbiology
- Type
- Comparative Study, Journal Article, Validation Study
- PMID
- 27927916
Original abstract
The precise diagnosis of American tegumentary leishmaniasis (ATL) is an essential task due to the disease's associated morbidity. A noninvasive, extremely sensitive, and highly specific exam is critical, particularly for mucosal leishmaniasis (ML), in which a low parasite quantity is expected. We aimed to compare the diagnostic accuracy of swab and biopsy sample analysis using SYBR Green- and TaqMan-based real-time PCR (qPCR) assays with that of a composite reference standard consisting of the Montenegro skin test, serology, histopathology, smears, culture, and conventional PCR. In total, 55 patients with ATL (ML, 18 patients; cutaneous leishmaniasis [CL], 37 patients) and 36 patients without ATL were studied. qPCR analysis of swabs was more accurate when using SYBR Green (87.88%; 95% confidence interval [CI], 77.86 to 93.73 patients) than when using TaqMan (78.79%; 95% CI, 67.49 to 86.92%) (P = 0.031). SYBR Green (84.72%; 95% CI, 74.68 to 91.25%) was also more accurate than TaqMan (73.61%; 95% CI, 62.42 to 82.41%) for biopsy samples (P = 0.008). All qPCR methods were 100% specific. Swabs and biopsy specimens had similar sensitivity when using the same chemistry (P = 0.125 for SYBR Green and P = 0.625 for TaqMan). Moreover, qPCR achieved better performance than most existing techniques used for the diagnosis of ATL and also detected the Leishmania parasite in a greater proportion of patients than the associated histopathology, smear, culture, and conventional PCR techniques did. Swabs therefore represent a useful diagnostic tool because they not only are noninvasive but also can achieve an accuracy similar to that of biopsy samples. The high accuracy of SYBR Green-based qPCR may also reduce the requirement for associated parasitological tests for ATL diagnosis.