Can clinical signs of trachoma be used after multiple rounds of mass antibiotic treatment to indicate infection?

PURPOSE: To evaluate combinations of clinical signs, using a modified World Health Organization (WHO) grading scheme, to predict a very low prevalence of infection at the community level after at least three rounds of mass drug administration (MDA).
METHODS: Seventy-one villages had three to seven rounds of MDA. A random sample of 7828 children ages 5 years and younger was evaluated for trachoma, and determination of Chlamydia trachomatis infection was made. Proportions of children positive for infection were evaluated against all possible combinations of follicular trachoma (TF) and inflammatory trachoma (TI). High-risk signs (HRS) for infection were defined as those indicating the infection prevalence was >20%. The sensitivity and specificity of prevalence of HRS in identifying communities with infection was examined.
RESULTS: The median community infection prevalence was 3.8% interquartile range (IQR) (1.8%, 7.7%); the median trachoma prevalence was 9.4%, IQR (6.6%, 15%). Severe TI, combination of TF and TI (WHO criteria), or severe TF with signs of inflammation were predictive of infection in the community, but the absence of these HRS was not an indicator of low infection rates.
CONCLUSIONS: The use of HRS to determine the infection status of a community was not useful in predicting whether MDA could be stopped.