A hematology analyzer is provided. In certain embodiments, the hematology analyzer comprises: a) a flow cell; b) a light source for directing light to the flow cell; c) a plurality of detectors for detecting a plurality of optical characteristics of a blood cell passing through the flow cell; and d) a data analysis workstation programmed to: i. enumerate test blood cells passing through the flow cell; and ii. flag a blood sample as containing lysis-resistant red blood cells or fragile white blood cells.