ASC/SIL ratio for cytotechnologists: A survey of its utility in clinical practice

The atypical squamous cell to squamous intraepithelial lesion (ASC/SIL) ratio for cytotechnologists (CTs) may correlate with screening sensitivity in some laboratory settings. Whether this ratio can be applied to other laboratory settings is not known. We conducted a survey of nine cytology laboratories and correlated the ASC/SIL ratio of individual CTs with other laboratory characteristics. The ASC/SIL ratio for individual CTs varied from 0.6 to 4.5 (mean: 1.9, median: 1.5). The ASC/SIL ratio within individual laboratories varied up to 567%; 25/78 (32%) CTs had an ASC/SIL ratio of less than 1.5, though only three of nine laboratories had more than one CT with a ratio this low. Laboratories that used 100% location guided screening (ThinPrep Imaging System) were much less likely to have a CT with a ratio <1.5 (1/20, 5%) than laboratories that never used location guided screening (14/34, 42%; P = 0.004). In addition, the normalized variance of these same laboratories that used location guided screening was significantly lower than those that did not (normalized standard deviation 0.32 vs. 0.55, P = 0.004). The ASC/SIL ratios did not correlate with laboratory volume, individual workload, or type of specimen preparation (conventional vs. liquid based). The ASC/SIL ratio for CTs varies widely between and within laboratories, and may correlate with the use of location guided screening. Very low ASC/SIL ratios are unusual, and CTs with low ratios may warrant further evaluation.