August 2014—The Clinical and Laboratory Standards Institute published H52-A2—Red Blood Cell Diagnostic Testing Using Flow Cytometry; Approved Guideline—Second Edition. This standard addresses the diagnostic red blood cell assays performed as fluorescence-based assays on a flow cytometry platform, including testing procedures for fetomaternal hemorrhage detection, paroxysmal nocturnal hematuria screening, membrane defect anemia testing for hereditary spherocytosis, and nucleated RBC counting. Caveats of interpretation and points of validation and quality control are also discussed.