Evaluation of less invasive sampling tools for the diagnosis of cutaneous Leishmaniasis

Background
Diagnosis of cutaneous leishmaniasis (CL) usually relies on invasive samples, but it is unclear whether more patient-friendly tools are good alternatives for diverse lesions when used with polymerase chain reaction (PCR).

Methods
Patients with suspected CL were enrolled consecutively in a prospective diagnostic accuracy study. We compared dental broach, tape disc, and microbiopsy samples with PCR as index tests, using PCR with skin slit samples as reference test. Subsequently, we constructed a composite reference test including microscopy, the 3 index tests and skin slit PCR, and we compared these same tests with the composite reference test. We assessed diagnostic accuracy parameters with 95% confidence intervals for all comparisons.

Results
Among 344 included patients, 282 (82.0%) had CL diagnosed, and 62 (18.0%) CL absence, by skin slit PCR. The sensitivity and specificity by PCR were 89.0% (95% confidence interval, 84.8%–92.1%) and 58.1% (45.7%–69.5%), respectively, for dental broach, 96.1% (93.2%–97.8%) and 27.4% (17.9%–39.6%) for tape disc, and 74.8% (66.3%–81.7%) and 72.7% (51.8%–86.8%) for microbiopsy. Several reference test–negative patients were consistently positive with the index tests. Using the composite reference test, dental broach, and skin slit had similar diagnostic performance.

Discussion
Dental broach seems a less invasive but similarly accurate alternative to skin slit for diagnosing CL when using PCR. Tape discs lack specificity and seem unsuitable for CL diagnosis without cutoff. Reference tests for CL are problematic, since using a single reference test is likely to miss true cases, while composite reference tests are often biased and impractical as they require multiple tests.