The use of polymerase chain reaction assay versus conventional methods in detecting neonatal chlamydial conjunctivitis.

PURPOSE To compare the performance of polymerase chain reaction versus conventional methods (cell culture and direct immunofluorescent assay) in diagnosing neonatal chlamydial conjunctivitis and their correlations to the severity of conjunctivitis. METHODS Consecutive cases of neonatal conjunctivitis were recruited over a year. Both eyes were clinically graded according to the severity of conjunctivitis and investigated using the three aforementioned chlamydial tests. Neonatal chlamydial conjunctivitis was assumed if one of these three tests was positive and there was clinical improvement after treatment. Sensitivity and specificity of each of the tests were analyzed. RESULTS Three hundred sixty-eight sets of chlamydial tests were done for 184 neonates. The percentage of positive results was 93.8% and 71.9% for polymerase chain reaction and conventional methods, respectively. Using positive results in either cell culture or direct immunofluorescent assay as a standard to diagnose neonatal chlamydial conjunctivitis, the sensitivity and specificity of polymerase chain reaction were 92.0% and 97.7%, respectively. If we used polymerase chain reaction as a standard, the sensitivity and specificity of cell culture were 73.3% and 99.7%, respectively. A discrepancy was noted in the number of positive results between polymerase chain reaction and conventional methods in milder disease. CONCLUSIONS Polymerase chain reaction might have a higher sensitivity and similar specificity in diagnosing neonatal chlamydial conjunctivitis compared to conventional methods, and it has an additional advantage as a diagnostic tool in mild disease.