INTERLABORATORY VARIATION IN DNA FLOW-CYTOMETRY - RESULTS OF THE COLLEGE-OF-AMERICAN-PATHOLOGISTS SURVEY

The results of the DNA Analysis Module of the College of American Path ologists' Flow Cytometry Survey were analyzed to determine if particip ating laboratories could correctly identify aneuploid populations and estimate S-phase fraction reproducibly in proficiency specimens. Each survey contained three specimens: a diploid calibrator and two unknown s comprising cultured aneuploid tumor cells with DNA indexes of 1.2 to 2.0 admired with normal lymphocytes. Results of ploidy analysis were obtained from a mean of 241 participants on 19 unknowns from 1990 to 1 992. Most laboratories correctly reported the modal (and intended) num ber of aneuploid peaks; the proportion of correct responses ranged fro m 58% to 97%, with a mean of 86%. The lower percents of correct respon se were associated with near-diploid and tetraploid unknowns. Some lab oratories showed consistent deviations from the mean for DNA index, in dicating apparent instrument linearity problems. S-phase results on fi ve specimens showed wide interlaboratory variability, although the mea ns of participants' responses were close to the reference values obtai ned by the specimen provider.