Application of Polymerase Chain Reaction in Diphtheria Laboratory Examination: A Field Need

Background: Indonesia is one of the five countries with the highest number of diphtheria cases worldwide. Diphtheria is caused by the toxigenic strains Corynebacterium diphtheriae, C. ulcerans, and C. pseudotuberculosis. The diphtheria-causing bacteria can be identified using conventional and molecular methods, including polymerase chain reaction (PCR) assay. We used the PCR assay as additional testing, because in island countries like Indonesia, specimen transport is a serious challenge to maintaining bacterial survival. Objectives: This study aimed to evaluate the PCR assay as additional testing to identify diphtheria-causing bacteria in the diphtheria laboratory. Methods: In this cross-sectional study, a total of 178 pairs of the throat and nasal swabs from diphtheria suspected cases and close contacts were collected from seven provinces in Indonesia in 2016. All samples were directly identified by the conventional method and multiplex PCR assay. Statistical analysis was conducted using the 2 × 2 tables to determine the sensitivity and specificity of both methods, while the χ2 test was used to examine the correlation between specimen examination delay and the differentiation of results. A P-value 72 hours’ specimen examination delay with a P-value of 0.04 (< 0.05). Conclusions: The PCR assay is more sensitive than the conventional method to identify diphtheria-causing bacteria and may be applied as additional testing to increase the positivity rate of diphtheria-confirmed cases in Indonesia as an archipelago country where geographical factors and specimen transport are real obstacles.