Acetic acid recovery of gynecologic liquid-based samples of apparent low squamous cellularity

To characterize cervicovaginal cytology samples with < 5,000 squamous cells on the initial ThinPrep slide (Cytyc Corp., Boxborough, Massachusetts, U.S.A) and to attempt sample recovery using acetic acid.

Cervicovaginal cytology samples with <5,000 squamous cells on the original ThinPrep slide and residuum were reprocessed by adding 3 mL of 3:1 CytoLyt (Cytyc)/glacial acetic acid with production of a second slide. Both slides were reviewed for squamous cell quantitation and the presence of background material and abnormal cells.

From a total of 1,833 cases, 147 (8.0%) were identified for reprocessing; 71 (48.3%) were grossly bloody and 58 (39.4%) grossly cloudy. Reprocessing resulted in a second slide with > 5,000 squamous cells in 116 (78.9%) cases and was most effective on cloudy samples (89.7% recovery) and bloody samples (71.8% recovery). Abnormal cells were identified in 13 (8.9%) reprocessed samples. In all but 2 cases the abnormal cells were present on the initial slide and demonstrated the same degree of abnormality as the reprocessed slide but were fewer in number.

Acetic acid recovery increases squamous cell recovery when initially inadequate, reducing the number of unsatisfactory cases and in rare cases identifying a cytologically significant lesion not apparent on the original slide.