New test for infection that causes blindness could be more effective than current detection method

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A new test for Chlamydia trachomatis the leading infectious cause of blindness maybe more effective than the current method for identifying infection, according to a paper in this week's issue of The Lancet.

Trachoma is a disease caused by repeated eye infection with certain types of C trachomatis. In 1995, nearly 6 million people were blind because of the disease. The World Health Organization (WHO) aims to eliminate trachoma by 2020 through adoption of the SAFE strategy (Surgery for people with trichiasis, Antibiotics to treat C trachomatis infection, Face cleanliness, and Environmental improvement). The A component is designed to treat C trachomatis infection and is currently initiated by the prevalence of clinical signs of trachomatous inflammation (TF). However, TF correlates poorly with the presence of infection.

Helen Lee and Claude-Edouard Michel from the University of Cambridge, UK, together with colleagues from the Kilimanjaro Centre of Community Ophthalmology, Moshi, Tanzania, the London School of Hygiene and Tropical Medicine, UK, and the Johns Hopkins University, Baltimore, MD, USA, compared a newly developed point-of-care (POC) assay for C trachomatis with the standard TF technique. The study involved 664 children from villages in Tanzania. They found that the new test had a higher specificity (proportion of people without infection who have a negative result, 99.4%) and sensitivity (proportion of people with infection who have a positive result, 83.6%) than the TF method.

Dr Lee states: "The POC assay assessed here has substantial advantages over the use of clinical signs. If the POC assay was to become widely available at low cost, it could help programmes reliably identify communities needing mass treatment with antibiotics."

Study collaborator Paul Courtright (Kilimanjaro Centre of Community Ophthalmology, Moshi, Tanzania) said: "The findings from the POC study will likely lead to a major re-think on how we conduct trachoma control in Africa. It will help us become more targeted in our approach--saving time and money." (Quote by e-mail; does not appear in published paper)

In an accompanying Comment, Hugh Taylor and Heathcote Wright from the University of Melbourne, Australia state: "We know that grading is quick, cheap, and reliable. We know it correlates with severity of disease, development of scarring, and ultimately progression to blindness. More work is needed to establish whether the new point-of-care test for infection will be more useful than clinical grading in the targeting and monitoring of SAFE-based programmes for trachoma control."

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Contact: Dr Helen H Lee, Department of Haematology, University of Cambridge, EABC Site, Long Road, Cambridge, CB2 2PT, UK. T) 01223 548080 hl207@cam.ac.uk

Comment: Professor Hugh R Taylor, Department of Ophthalmology, Centre for Eye Research Australia, The University of Melbourne, Locked Bag 8, 32 Gisborne Street, East Melbourne 8002, Australia. T) +61 3 9929 8368 h.taylor@unimelb.edu.au


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