- Serum bilirubin levels ≤1.5 x the upper limit of the normal (ULN) range for the laboratory; higher levels are acceptable if these can be attributed to active hemolysis (as indicated by positive direct Coombs' testing, decreased haptoglobin level, elevated indirect bilirubin and/or lactate dehydrogenase), or ineffective erythropoiesis (as indicated by bone marrow findings);