h MICL and CD 123 in combination with a CD 45/ CD 34/ CD 117 backbone – a universal marker combination for the detection of minimal residual disease in acute myeloid leukaemia

Summary Real‐time quantitative polymerase chain reaction (q PCR ) has been extensively validated for the detection of minimal residual disease ( MRD ) in acute myeloid leukaemia ( AML ). Meanwhile, multicolour flow cytometry ( MFC ) has received less attention because the so‐called leukaemia‐associated immunophenotypes ( LAIP s) are generally of lower sensitivity and specificity, and prone to change during therapy. To improve MRD assessment by MFC , we here evaluate the combination of human Myeloid Inhibitory C ‐type L ectin (h MICL , also termed C ‐type lectin domain family 12, member A , CLEC 12 A ) and CD 123 (also termed interleukin‐3 receptor alpha, IL3RA ) in combination with CD34 and CD117 ( KIT ), as an MRD assay in pre‐clinical and clinical testing in 69 AML patients. Spiking experiments revealed that the assay could detect MRD down to 10 −4 in normal bone marrow with sensitivities equalling those of validated q PCR assays. Moreover, it provided at least one MFC MRD marker in 62/69 patients (90%). High levels of h MICL / CD 123 LAIP s at the post‐induction time‐point were a strong prognostic marker for relapse in patients in haematological complete remission ( P  <   0·001). Finally, in post induction samples, h MICL / CD 123 LAIPs were strongly correlated ( r  = 0·676, P  =   0·0008) to applied q PCR targets. We conclude the h MICL / CD 123‐based MFC assay is a promising MRD tool in AML .