Development and Evaluation of a PCV-Dependent Visual Hemolysis Color Scale for Packed Red Blood Cell Products

To develop a PCV-dependent hemolysis color scale and evaluate its accuracy in predicting supernatant hemoglobin concentration in packed red blood cell (pRBC) products, helping to determine transfusion safety.

Prospective experimental study.

University veterinary teaching hospital.

Serial dilutions of a pRBC unit were performed to create a range of hemolyzed supernatant samples. A commercial graphics program was used to allocate computerized color to each hemolyzed sample, constructing a color scale. Study participants were then asked to use the color scale to estimate the hemoglobin concentration of a provided supernatant sample. The color estimation data were analyzed by the authors to determine whether to transfuse blood, as pRBC should not be transfused if the product's percentage hemolysis is >1%.

Visual inspection with the color scale was evaluated with seven supernatant test samples containing different free hemoglobin concentrations (0.3-8.0 g/L). The percentage of correct color estimation overall was 61.9%. The percentage of correct decisions to transfuse the blood product overall would have been 93.7%. All incorrect estimations were one color range (approximately 1.0 g/L difference between the ranges) off from the correct estimation for all samples.

The color scale aided the visual assessment of hemolysis. However, visual inspection with the color scale can still be inaccurate near the corresponding cutoff color of <1% hemolysis in each PCV range. If the supernatant color of the unit is estimated to be one color range off from the cutoff color, the cell-free hemoglobin concentration of the unit should be measured, and percentage hemolysis should be calculated to determine if it meets the <1% hemolysis standard.