negative controls). Results were compared with the diagnoses revealed by cytomorphology (CM) and cytogenetics (CG).Results: Percentages of granulocytes and monocytes with diminished MNDA expression (dimG and dimM) were higher in patients with MDS (mean 6 SD, 20% 6 20%, P < 0.001 and 31% 6 24%, P < 0.001) and AML (27% 6 27%, P 5 0.007 and 45% 6 31%, P 5 0.001) diagnosed by CM, vs. patients without MDS (8% 6 10% and 16% 6 11%), respectively. Significant differences were also found for mean fluorescence intensity (MFI) of MNDA in monocytes which was lower in MDS (mean 6 SD, 71 6 36, P 5 0.004) and AML (55 6 39, P < 0.001) vs. no MDS samples (85 6 28), respectively. Within patients with MDS, cases with cytogenetic aberrations showed a trend to higher %dimG (24% 6 18%, P 5 0.083) compared with those without (16% 6 21%). Cut-off values for %dimG (12%) and %dimM (22%) as well as for MFI in monocytes (72) were defined capable of discriminating between MDS and non-MDS.Conclusion: MNDA expression in bone marrow cells can be assessed reliably by MFC and may facilitate evaluation of dyspoiesis when added to a standard MDS MFC panel. V C 2012 International Clinical