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

Abstract

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.

Keywords::

• Chlamydia trachomatis
• diagnosis
• digital droplet PCR
• PCR
• trachoma

Financial & competing interests disclosure

The author has received honoraria for speaking, consulting fees or research support from Pfizer, Becton-Dickinson, Cepheid, GenProbe, Hologic, Qiagen and Roche. The author has also co-authored papers with some of the co-authors of the paper under review. The author has no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

Key issues

• • There is a large effort underway to eliminate blinding trachoma as a public health problem. Community wide azithromycin treatment is essential to complete this program.

• • Azithromycin treatment quickly reduces the prevalence of Chlamydia trachomatis, yet clinical disease persists longer. This is a problem, as control efforts are monitored by clinical findings.

• • There is a need for a sensitive specific diagnostic test for C. trachomatis, particularly if it could be used for assessment of trachoma control efforts.

• • Roberts et al. adapted droplet digital PCR (ddPCR) to detect and quantify C. trachomatis ocular infections.

• • When they compared ddPCR to Roche's Amplicor® on conjunctival swab specimens collected in a trachoma endemic area ddPCR sensitivity was 73.3%.

• • They concluded that “ddPCR is an effective diagnostic technology suitable for both research and clinical use in diagnosing ocular C. trachomatis infections.”

• • Lower sensitivity of ddPCR is a serious flaw which worried the reader.

• • It is suggested that there are more sensitive, commercially available NAATs that can be used for quantification and that may offer practical advantages.