Abstract
PurposeTo determine the sensitivity, specificity, and field utility of the Cepheid GeneXpert Chlamydia trachomatis (CT) Assay (GeneXpert) for ocular chlamydia infection compared to Roche Amplicor CT assay (Amplicor).MethodsIn a trachoma-endemic community in Kongwa Tanzania, 144 children ages 0 to 9 were surveyed to assess clinical trachoma and had two ocular swabs taken. One swab was processed at Johns Hopkins University, Baltimore MD, using Amplicor, (Roche Molecular Diagnostics) and the other swab was processed at a field station in Kongwa using the GeneXpert Chlamydia trachomatis/Neisseria gonorrhoeae assay (Cepheid). The sensitivity and specificity of GeneXpert was compared to the Amplicor assay.ResultsOf the 144 swabs taken the prevalence of follicular trachoma by clinical exam was 43.7%, and by evidence of infection according to Amplicor was 28.5%. A total of 17 specimens (11.8%) could not be processed by GeneXpert in the field due to lack of sample volume, other specimen issues or electricity failure. The sensitivity of GeneXpert when compared to Amplicor was 100% and the specificity was 95%. The GeneXpert test identified more positives in individuals with clinical trachoma than Amplicor, 55% versus 52%.ConclusionThe GeneXpert test for C. trachomatis performed with high sensitivity and specificity and demonstrated excellent promise as a field test for trachoma control.
Highlights
Trachoma, a chronic conjunctivitis caused by repeated infection with Chlamydia trachomatis (CT), is currently the leading cause of infectious blindness [1]
First reported after Mass Drug Administration (MDA) in the Azithromycin in Control of Trachoma Trial [4], infection declined at one year in Tanzania, from 20% to 7%, but the decline was less marked for clinical trachoma, which declined from 64% to 42%
The prevalence of trachoma and ocular CT infection was determined for the 144 eye samples
Summary
A chronic conjunctivitis caused by repeated infection with Chlamydia trachomatis (CT), is currently the leading cause of infectious blindness [1]. First reported after Mass Drug Administration (MDA) in the Azithromycin in Control of Trachoma Trial [4], infection declined at one year in Tanzania, from 20% to 7%, but the decline was less marked for clinical trachoma, which declined from 64% to 42%. This finding is not unexpected, as research in animals has reported a longer time for resolution of clinical signs following the clearance of infection [5] Several investigators working in trachoma endemic countries have reported that between 40–60% of clinical follicular trachoma seen in children may not have infection [6,7,8]. Data on the prevalence of infection may be a useful adjunct to the Author Summary
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