Will droplet digital PCR become the test of choice for detecting and quantifying ocular Chlamydia trachomatis infection? Maybe not.

Evaluation of: Roberts CH, Last A, Molina-Gonzalez S et al. Development and evaluation of a next-generation digital PCR diagnostic assay for ocular chlamydia trachomatis infections. J. Clin. Microbiol. 51(7), 2195-2203 (2013). Trachoma is the leading infectious cause of blindness in developing countries. Currently, there is no program to eliminate blinding trachoma as a public health problem. We need better diagnostic tests for research and to assess progress in control programs. Roberts et al. adapted droplet digital PCR (ddPCR), an emulsion PCR process that performs absolute quantitation of nucleic acids, to detect and quantify Chlamydia trachomatis infections. They compared the results with ddPCR on conjunctival swab specimens collected in trachoma-endemic area to results using Roche's Amplicor® C. trachomatis/Neisseria gonorrhoeae (CT/NG) PCR and found that ddPCR sensitivity was 73.3%. The authors concluded that 'ddPCR is an effective diagnostic technology suitable for both research and clinical use in diagnosing ocular C. trachomatis infections'. This reviewer disagrees, feeling that if the stated sensitivity is accurate, it is too low, and suggests there may be good reasons to adapt commercially available tests for this purpose.