How is hemolytic anemia workup?

The DAT result is usually positive in autoimmune hemolytic anemia (AIHA), but it may occasionally be negative in this disorder. From 5-10% of all AIHAs are DAT negative. DAT-negative AIHA has a better prognosis than DAT-positive AIHA. In addition to hemoglobinuria, either myoglobinuria or porphyria may result in dark urine. To rule out these possibilities, the urine should be tested for free hemoglobin. Hemoglobinuria occurs when the amount of free hemoglobin released during hemolysis exceeds available haptoglobin. Note that haptoglobin is not a reliable way to differentiate between intravascular and extravascular hemolysis