Trichiasis With and Without Tarsal Conjunctival Scarring: a multi-country observational study

There has been discussion regarding the definition of the clinical sign trachomatous trichiasis (TT) for the purposes of determining elimination of trachoma as a public health problem, and whether the definition should include the presence of trachomatous scarring (TS). A multi-country observational study was conducted in settings with varying TT burdens in Ethiopia, Uganda and Nigeria to determine if the TS grading collected from trichiasis cases by field graders in trachoma surveys using a simplified grading scheme are comparable with tarsal conjunctival scarring (TCS) grading by experts using a detailed grading scheme. The primary outcome was the proportion of eyes that were originally graded in the surveys as "No TS" but had some degree of TCS from expert photographic grading (the negative predictive value, NPV). In Ethiopia, Uganda and Nigeria, 545 (438 cases and 107 comparisons), 256 (156 trichiasis cases and 100 comparisons), and 468 (352 trichiasis cases and 116 comparisons) participants, respectively, were enrolled. In Ethiopia, among 111 trichiatic eyes graded "No TS" in the surveys, 103 (92.8%) had TCS in expert photo grading, NPV 7.2% (95% CI 3.2%- 13.7%). In Uganda, among 28 trichiatic eyes graded "No TS" in the surveys, 19 (67.9%) had TCS in expert photo grading, NPV 32.1% (95% CI 15.9%-52.4%). In Nigeria, among 111 trichiatic eyes graded "No TS" in the surveys, 100 (90.1%) had TCS in expert photo grading, NPV 9.9% (95% CI 5.0%-17.0%). Among eyes misdiagnosed as "No TS" in the survey grading in all the three settings, 174/250 (69.6%) were those with extensive TCS (patches of scarring occupying [≥]1/3 of the upper tarsal conjunctiva). Trichiatic eyes with TCS had more severe entropion, trichiasis, conjunctival inflammation, and corneal opacity than those without TCS. In all three settings, including TS to define a trichiasis "trachomatous" in a survey could result in the underestimation of the burden of TT. However, TCS can be effectively used to determine TT severity and management.