Comparison of an rRNA-based and DNA-based nucleic acid amplification test for the detection of Chlamydia trachomatis in trachoma

BACKGROUND/AIM: The World Health Organisation (WHO) hopes to achieve global elimination of trachoma, still the leading cause of preventable blindness worldwide, in part through mass antibiotic treatment. DNA-based nucleic acid amplification tests (NAATs) are currently used to evaluate the success of treatment programmes by measuring the prevalence of C trachomatis infection. Some believe that newer ribosomal RNA (rRNA)-based tests may be much more sensitive since bacterial rRNA is present in amounts up to 10 000 times that of genomic DNA. Others believe that rRNA-based tests are instead less sensitive but more specific, due to the presence of dead or subviable organisms that the test may not detect. This study compares an rRNA-based test to a DNA-based test for the detection of ocular C trachomatis infection in children living in trachoma-endemic villages. METHODS: An rRNA-based amplification test and DNA-based polymerase chain reaction (PCR) were performed on swab specimens taken from the right upper tarsal conjunctiva of 56 children aged 0-10 years living in two villages in Amhara, Ethiopia. RESULTS: The rRNA-based test detected ocular C trachomatis infection in 35 (63%) subjects compared with 22 (39%) detected by PCR (McNemar's test, p = 0.0002). The rRNA-based test gave positive results for all subjects that were positive by PCR, and also detected infection in 13 (23%) additional subjects. CONCLUSION: The rRNA-based test appears to have significantly greater sensitivity than PCR for the detection of ocular chlamydial infection in children in trachoma-endemic villages. Using the rRNA-based test, we may be able to detect infection that was previously missed with PCR. Past studies using DNA-based tests to assess prevalence of infectious trachoma following antibiotic treatment may have underestimated the true prevalence of infection.