Complex measurements may be required to establish the prognostic impact of immunophenotypic markers in AML

[Objectives]: The prognostic impact of immunophenotypic markers in acute myeloid leukemia (AML) is controversial. [Methods]: We retrospectively analyzed the value of CD34, CD117, CD7, and CD123 expression in a consecutive series of 592 adult patients with de novo AML. [Results]: CD34+ measured as a percentage (≥2.88%) and CD34 mean fluorescence intensity (MFI) (≥146.79, arbitrary units [AU]) expression had a prognostic impact in terms of overall survival (OS; P = .005, P = .003), leukemia-free survival (LFS; P = .011, P <.001), and cumulative incidence of relapse (CIR; P = .014, P =. 001). The percentage of CD117+ cells (61.29%) was associated with shorter LFS (P =. 043), and CD117 MFI (≥284.01 AU) was associated with a shorter OS (P =. 033) and LFS (P =. 028). In the multivariate analysis, high CD34 MFI retained the independent value as predictor of LFS and CIR (P =. 012; hazard ratio [HR], 1.59; 95% confidence interval [CI], 1.11- 2.28 and P =. 045; HR, 1.58; 95% CI, 1.01-2.46). [Conclusions]: CD34 positivity threshold with prognostic relevance is low (3% positive cells). Immunophenotypic findings in AML probably could only be fully exploited after a complex analysis that takes into account unconventional thresholds and the MFI.