Comparison of cytologic and acridine-orange flow-cytometric detection of malignant cells in human body cavity fluids

Flow cytometrically (FCM) derived DNA and RNA profiles were studied in acridine orange (AO)-stained body cavity fluid (BCF) specimens obtained from 78 patients with various solid tissue and hematologic malignancies. The ploidy (DNA index), RNA content (RNA index), proliferative activity (% S + G₂M) and DNA and RNA scattergram patterns were tested 'double-blind' against the cytologic scoring of specimens as malignant, benign or reactive. It was determined that expression of an 'abnormal' RNA index (≥2.8) and an elevated proliferative activity (% S+ G₂M ≥ 7.4) was dependent on the presence of malignancy; 21 of 22 specimens having ghose abnormal indices had DNA aneuploidy and were cytologically scored as positive. The AO FCM sensitivity and specificity for detecting malignant cells (when measured against cytology scoring) were 61% ad 90%, respectively, using the 'abnormal' RNA index and % S + G₂M cut-offs together with the cellular DNA aneuploidy marker. By supplementing the cytologic scoring with AO FCM DNA and RNA features, the sensitivity for detecting malignant cells was 94%, as compared to 72% for cytology alone. Two specimens gave false-positive FCM results: a tuberculous effusion with a tetraploid subpopulation and a reactive mesothelial proliferation that was diploid and negative cytologically. Scoring for malignancy based on the visual pattern of the DNA and RNA FCM scattergrams, while showing good correlation for aneuploid specimens, in some cases failed to identify diploid disease. The results demonstrate the usefulness of FCM DNA and RNA analysis for supplementing cytologic examination of BCF specimens for the purpose of detecting malignant cells. In diploid tumors, however, the addition of the RNA and proliferative indices was of little value, except for the hematologic malignancies.