Hydroxocobalamin infusion in a patient monitored for plasma free hemoglobin levels

Hemolysis is one of the most common preanalytical concerns in the clinical laboratory. Hydroxocobalamin administration causes red pigmentation of plasma that may mimic hemolysis and may interfere with chemistry assays. A male patient in his sixties was placed on extracorporeal membrane oxygenation (ECMO) as a bridge to transplantation. Daily plasma free hemoglobin measurements were ordered to monitor for adverse ECMO events. An intensely red plasma specimen was inconsistent with modestly elevated hemoglobin levels and became pink on dilution. Follow-up with providers indicated that the red plasma could be attributed to hydroxocobalamin administration. Performance of scanning spectrophotometry and assessment of a sample spiked with hydroxocobalamin indicated that the red colored hydroxocobalamin did not interfere with our 3,3',5,5'-tetramethylbenzidine based methodology for free plasma hemoglobin measurement. It is important for the laboratory professionals to be aware of the possibility of interference in hemoglobin assays due to hydroxocobalamin.