Can corneal pannus with trachomatous inflammation--follicular be used in combination as an improved specific clinical sign for current ocular Chlamydia trachomatis infection?

Tamsyn Derrick,Robin L Bailey,Rod Markham-David,Anna R Last,Eunice Cassama,Meno Nabicassa,Michael Marks,Martin J Holland

doi:10.1186/s13071-016-1308-9

Tamsyn Derrick, Robin L Bailey + Show 6 more

Open Access

https://doi.org/10.1186/s13071-016-1308-9

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Abstract

BackgroundTrachoma is a blinding disease caused by conjunctival infection with Chlamydia trachomatis (Ct). Mass drug administration (MDA) for trachoma control is administered based on the population prevalence of the clinical sign of trachomatis inflammation – follicular (TF). However, the prevalence of TF is often much higher than the prevalence of Ct infection. The addition of a clinical sign specific for current ocular Ct infection to TF could save resources by preventing unnecessary additional rounds of MDA.MethodsStudy participants were aged between 1–9 years and resided on 7 islands of the Bijagos Archipelago, Guinea Bissau. Clinical grades for trachoma and corneal pannus and ocular swab samples were taken from 80 children with TF and from 81 matched controls without clinical evidence of trachoma. Ct infection testing was performed using droplet digital PCR.ResultsNew pannus was significantly associated with Ct infection after adjustment for TF (P = 0.009, OR = 3.65 (1.4–9.8)). Amongst individuals with TF, individuals with new pannus had significantly more Ct infection than individuals with none or old pannus (75.0 % vs 45.5 %, Chi2P = 0.01). TF and new pannus together provide a highly specific (91.7 %), but a poorly sensitive (51.9 %) clinical diagnostic test for Ct infection.ConclusionsAs we move towards trachoma elimination it may be desirable to use a combined clinical sign (new pannus in addition to TF) that is highly specific for current ocular Ct infection. This would allow national health systems to obtain a more accurate estimate of Ct population prevalence to inform further need for MDA without the expense of Ct molecular diagnostics, which are currently unaffordable in programmatic contexts.

Highlights

Trachoma is a blinding disease caused by conjunctival infection with Chlamydia trachomatis (Ct)
In this study we evaluated the use of corneal pannus as a clinical sign for Ct infection using field observed grades, analogous to how it would be implemented by national trachoma control programmes
Chlamydial load increased with trachomatis inflammation – follicular (TF) grade, but there was no apparent relationship between pannus and Ct load (Table 1)

Summary

Introduction

Trachoma is a blinding disease caused by conjunctival infection with Chlamydia trachomatis (Ct). Mass drug administration (MDA) for trachoma control is administered based on the population prevalence of the clinical sign of trachomatis inflammation – follicular (TF). The addition of a clinical sign specific for current ocular Ct infection to TF could save resources by preventing unnecessary additional rounds of MDA. Trachoma is the most common infectious cause of blindness worldwide and is initiated by conjunctival infection with Chlamydia trachomatis (Ct). It is currently estimated that ~21.4 million people have active trachoma [1], many of whom will go on to develop the scarring sequelae that can lead to blindness. When the baseline prevalence of TF in 1–9 year olds (TF1–9) is between 10–29 % the WHO recommends that 3 years of annual mass drug administration (MDA) with Azithromycin should be delivered, extending to 5 years when TF1–9 is ≥30 %. If a district has TF1–9 between 5–10 %, within-district communities should be assessed and treated separately by the same principles and F and E should continue

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