Comparability of two fundus photograph reading centers in grading cytomegalovirus retinitis progression

Purpose To compare grading of cytomegalovirus retinitis progression by two different fundus photograph reading centers (FPRCs). Design Patients with AIDS followed in an ophthalmology service were enrolled in a prospective epidemiologic study of the prevalence and incidence of resistant cytomegalovirus in vitro. Methods We compared masked replicate gradings by two different FPRCs of monthly fundus photographs for retinitis progression (onset of a separate new lesion or expansion of an existing lesion by ≥one-half disk diameter). Results For 77 patients, Kaplan-Meier plots of progression over time were similar between FPRCs (median time to progression, 65 vs 69 days). Agreement between FPRCs was 51% (kappa [κ] = .37, "fair") on exact visit of progression (28 patients) or on absence of progression through follow-up (11 patients) and 62% (κ = .38) on progression visit ± 1 month. Eight of 12 patients with progression graded as more than 1 month apart were only 2 months apart. Considering each monthly visit as a choice point, overall agreement on progression was 78% (κ = .55, "moderate"). Baseline evaluation of retinitis showed 95% agreement on presence/absence and a concordance correlation coefficient of .75 for extent in combined zones 1 and 2. Rates of retinal loss over follow-up were estimated as 2.8%/month vs 2.0%/ month (P = .015). Conclusions By adopting similar protocols and procedures, different FPRCs can achieve good agreement on presence and extent of cytomegalovirus retinitis. Further efforts to harmonize evaluation through ongoing comparison of gradings would likely improve agreement on retinitis progression.