An in vitro method for predicting the efficacy of WBC separation casing different starch preparations and anticoagulant ratios

BACKGROUND: Separation of blood components depends on a number of factors, including the viscosity of the plasma and the number and size of the variou s cellular elements. To enhance granulocyte collection, it is common practi ce to alter the plasma environment by the addition of sedimenting agents su ch as hydroxyethyl starch. Recently, because of its prolonged persistence i n the circulation, the higher-molecular-weight form of hydroxyethyl starch, Hespan (HP), has been replaced by the lower-molecular-weight form, pentast arch (PS). However, the yield appears to be lower. A rapid in vitro approac h was used to permit comparison of the efficiency of separation of WBCs by the use of PS and HP and different ratios of anticoagulants that also alter the sedimenting characteristics of blood. STUDY DESIGN AND METHOD: Blood from individual persons was collected into s odium citrate at ratios of 1:8, 1.12, and 1:16. Samples were evaluated eith er before or after the addition of PS or HP and after centrifugation. RESULTS: The addition of HP increased the sedimentation rate to at least fo ur times that of plasma (10.9 vs. 47.9 mm); PS approximately doubled the ra te. Viscosity was altered by the introduction of either starch. These chang es (ranging from a rate of 4.2 in HP with a 1:16 anticoagulant to 3.6 in PS with a 1:8 ratio of anticoagulant) reflected the anticipated effects of an ticoagulant dilution and carbohydrate addition. Granulocyte recovery was hi ghest, with a 1:12 anticoagulant ratio in all tests with HP producing the g reatest yield (HF: 101%; PS, 89%; control, 78%). CONCLUSION: HP is far more effective than its lower-molecular-weight substi tute PS in the generation of granulocytes in the buffy coat of whole blood. This method provides a simple, rapid, in vitro approach to evaluating the separating efficiency of solutions.