THE EFFECT OF NUMBER OF HISTOGRAM EVENTS ON REPRODUCIBILITY AND VARIATION OF FLOW CYTOMETRIC PROLIFERATION MEASUREMENT

Sources of variation in synthesis phase fraction (SPF) calculation wer e studied, and the number of histogram events was found to be an impor tant quality control consideration. Sis cell cycle models (CCMs) for h istograms composed of 1,000 to 20,000 events were compared. All CCMs w ere cytometer based, or available in Multicycle (MC) software. The exp eriment consisted of five consecutive acquisitions, on the same day, o f the same propidium iodide (PI) stained sample of T24 human cell line , at each of nine ''landmarks'' between 1,000 and 20,000 events. The a uthors found (1) all CCMs evaluated required greater than or equal to 5,000 events for accurate, reproducible SPF; and (2) in the 5,000-20,0 00 event range the MC models provided the most accurate, reproducible SPF values. Therefore, histogram-dependent curve fitting models may en hance clinical applications of FCM proliferation measurements. The aut hors conclude that histogram rejection criteria for S-phase analysis s hould be established, and that two-color multiparametric DNA analysis ''live'' gating with tissue specific markers may assure acquisition of sufficient events for accurate SPF.