Measurement of hemolysis in packed red blood cell segments and units using H index

Packed red blood cell (pRBC) units are tested before transfusion to confirm compatibility, safety, and quality. Segments are lengths of heat-sealed tubing from the pRBC unit that enable compatibility testing without compromising sterility. If the degree of hemolysis differs between the segment and the parent unit, hematologic or metabolic testing of segments may lead to inaccurate assessment of the corresponding unit. We directly compared hemolysis indices between paired pRBC units and their corresponding segments to assess the degree of hemolysis and possible association with pRBC unit characteristics.

Discarded pRBC units bearing at least 1 attached segment were obtained from a university hospital blood bank. Recorded characteristics included product expiration date, ABO/Rh type, and anticoagulant/additive solutions. Supernatant plasma was analyzed for hemolysis using the Roche cobas 8000 automated chemistry system H index. Associations between the H index and pRBC unit characteristics were also evaluated.

A total of 42 paired pRBC units and corresponding segments were analyzed. The segment H index was statistically significantly higher than that of parent units (median [IQR], 309 [189-512] vs 98 [72-177]; Wilcoxon signed rank P < .001), with 39 of 42 (93%) paired samples demonstrating a higher H index in segments. The H index increased with the number of days past expiration both for segments (Spearman ρ = 0.69) and parent units (ρ = 0.61; both P < .001). No statistically significant association between H index and ABO blood group, Rh type, or additive solution type was identified.

Our investigation revealed that pRBC segments had statistically significantly increased hemolysis compared with corresponding parent units. As a result, caution should be taken when using segments to assess hemolysis and other hematologic or metabolic testing.