High frequency of low plasma haptoglobin values found in hemophilia A patients on prophylactic treatment with factor VIII concentrates - a sign of hemolysis?

Low plasma haptoglobin values have been observed in hemophilia A patients on regular prophylactic treatment with factor VIII concentrates. Two of 3 patients treated with fraction I-0 (Kabi) and 7 of 11 patients treated with high-purity concentrates (Hyland) had low haptoglobin values. Four of 8 patients who were treated with high-purity concentrates prescreened for a low content of anti-A and anti-B immunoglobulins still showed low haptoglobin levels. Unexpectedly, 2 patients of blood group 0 showed low haptoglobin values. The presence of irregular erythrocyte alloantibodies and/or other contaminants of the concentrates might thus also be a cause of hemolysis resulting in an increased consumption of haptoglobin. Elevated lactate dehydrogenase levels were also frequent. No correlations were found between albumin, aspartate or alanine aminotransferase levels and haptoglobin levels.