Dry reagent-based polymerase chain reaction compared with other laboratory methods available for the diagnosis of Buruli ulcer disease

Abstract

Background: Because of the multifaceted clinical presentation of Buruli ulcer disease, misclassification of clinically diagnosed cases may occur frequently. Laboratory tests for the confirmation of suspected cases include microscopic examination, culture, polymerase chain reaction (PCR), and histopathologic examination. However, microscopic examination, the only test usually available in areas of endemicity, has a low sensitivity.

Methods: To make a highly sensitive diagnostic method locally available, dry reagent-based PCR (DRB-PCR), which is well adapted to tropical conditions, was pilot-tested in Ghana. Subsequently, the assay was used for the routine diagnosis of Buruli ulcer disease over a period of 2 years. The method was compared with other diagnostic tests to evaluate its performance under field conditions.

Results: The interassay agreement rate between DRB-PCR and standard PCR was 91.7% for swab specimens and 95% for tissue specimens. Among all of the locally available tests, DRB-PCR revealed the highest overall positivity ratio. Sixty percent of patients with clinical diagnoses of Buruli ulcer disease had the diagnoses confirmed by DRB-PCR of swab or tissue specimens, compared with 30%-40% of patients who had diagnoses confirmed by microscopic examination of swab or tissue specimens. The positivity ratio of DRB-PCR varied considerably when analyzed per treatment center. Standardization of specimen collection resulted in a 30% increase in the positivity ratio of the assay, compared with that in the pilot-testing phase.

Conclusions: DRB-PCR is a reliable tool for the diagnosis of Buruli ulcer disease. However, PCR assays are suitable for detection only during early stages of the disease, when samples still contain bacilli. The quality of clinical diagnosis and the quality of diagnostic specimens strongly influence the positivity ratio.