Trachoma grading: observer trials conducted in southern Malawi.

A variety of grading schemes have been proposed for the clinical classification of inflammatory trachoma. During a population based study of ocular disease conducted in southern Malawi we tested a simplified version of the current WHO grading scheme. Intraobserver agreement statistics were less than satisfactory for three of four graders. Interobserver agreement when compared against either a well experienced standard ophthalmologist or a consensus grade improved over time for two of the three graders. However, initial agreement for all three graders was only fair to moderate. Previous studies of trachoma grading schemes support these unsatisfactory results. A new system of classification is needed that is both accurate and reliable in a field setting.