Fig. 3

Diagnosis flowsheet. In the context of a direct antiglobulin test (DAT)-negative hemolysis, a blood smear needs to be performed. If Heinz bodies and/or bite cells are present, consider the following differential diagnoses: glucose-6-phosphate dehydrogenase (G6PD) deficiency, unstable hemoglobinopathies, or hemoglobin H disease. Then, perform G6PD enzyme testing. If normal, consider isopropanol heat stability testing. This test is optional; be aware that false positive may occur if hemoglobin F is high or in case of methemoglobinemia [1]. The next step would be hemoglobin electrophoresis/high-performance liquid chromatography (HPLC). Independently of the result, genetic testing is recommended. Indeed, hyperunstable variants may undergo rapid denaturation and degradation, so that the remaining Hb may appear normal. Therefore, normal Hb electrophoresis/HPLC result does not exclude unstable hemoglobinopathy, and genetic testing needs to be conducted [12, 13].