Effect of Blood Transfusion On Serum Haptoglobin.

Haptoglobin, an alpha2 globulin, is an acute phase reactant, which functions to bind the globin portion of free hemoglobin in the blood. The half-life of serum haptoglobin is approximately five days, but in the presence of free hemoglobin, the hemoglobin-haptoglobin complex is rapidly cleared from the system causing a decrease in the measured serum haptoglobin (normal levels 36-195mg/dl). The measurement of serum haptoglobin is used as one of the laboratory markers for the diagnosis of hemolytic anemia. Since stored blood contains a variable amount of free hemoglobin, transfusion of this blood may affect haptoglobin levels and thereby negate the usefulness of haptoglobin measurement when hemolysis is suspected in recently transfused patients.

Twenty-0ne patients, who were being transfused with more than one unit of packed red blood cells (PRBC), for non-hemolytic indications, were enrolled in the study and their serum haptoglobin levels were recorded before, immediately after, 24 hours after and 48 hours after PRBC transfusion.

A total of twenty-one patients were enrolled in the study and these patients received a total of forty-seven units of PRBC. The most common indication for transfusion was anemia secondary to blood loss. Eighteen patients received two units, one patient received three units, and two patients received four units of PRBC. Four patients received PRBC's that were more than 30 days old. When blood less than 30 days old was transfused there was a decrease to below normal in the haptoglobin level of only one patient, and this patient had a low normal serum haptoglobin level prior to transfusion. However, in four patients who received blood that was more than 30 days old, two (fifty percent) had a decrease in serum haptoglobin levels to below normal.

Serum haptoglobin can be used in the diagnosis of hemolysis in patients receiving multiple units of PRBC transfusions when the age of the transfused blood is less than thirty days. However, when PRBC's more than thirty days old are transfused measurement of serum haptoglobin might not prove to be a reliable indicator of hemolysis. Further studies with larger sample sizes are needed to confirm our findings.

No relevant conflicts of interest to declare.