Assessment of agreement for assignment of a normal grade to human conjunctival impression cytology samples

Assessment of agreement for assignment of a normal grade to human conjunctival impression cytology samples Objective: To assess the level of agreement for assignment of a normal grade for human ocular surface bulbar conjunctival cells as collected by conjunctival impression cytology. Methods: Suitable images from published articles that included a scale marker were subjected to the same planimetry method to assess cell area, nucleus area, long (L) and short (S) dimensions of the cells and the nucleus. These measures, along with the nucleus-to-cytoplasmic (N/C) ratio, were compared. Results: Area measures on normal grade images indicated a broad unimodal distribution (250-275 mu m2), and distribution of nucleus area values was heterogeneous, with neither being normally distributed. The inter-sample variance for any particular area value ranged from 11 to 90% (group averages of 49%). The L:S dimension ratio averaged 1.288, consistently showing these cells are not round. N/C values showed a wide range (from 0.151 to 0.655), as did nucleus-to-cytoplasm dimensions (from 0.332 to 0.603). Conclusions: Current criteria for subjective assignment of a normal grade to bulbar conjunctival cells do not appear to be robust enough to allow for inter-sample comparison. Quantitative measures need to be developed further.