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

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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.


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.


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.


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.

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