HLA-B and Absence of circulating granulocytes: We considered the HLA-DQB1 and HLA-B alleles in schizophrenic patients treated with clozapine to prevent agranulocytosis either by restricting ANCM to patients with the alleles of susceptibility (GGS) or by foregoing ANCM in all patients and selecting an alternative antipsychotic drug instead for patients with HLA alleles of susceptibility (CSS strategy).