A new radioimmunoassay for the detection of small amounts of white cells and platelets in red cell concentrates: implications for blood transfusion

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Abstract
In the procedure for quality control of red cell concentrates, made white cell (WBC)-poor by filtration, the particle-counting technique was found to be insufficiently sensitive in detecting the remaining WBCs and platelets. Therefore, direct radioimmunoassays were developed using murine monoclonal antibodies specific for platelets, granulocytes, and T lymphocytes. The sensitivity for platelets was 40 .times. 103 per mL, that for granulocytes was 10 .times. 103 per mL (starting from 0.3 mL or red cell filtrate), and that for T lymphocytes was 0.006 .times. 106 per mL (starting from 5 mL) and 0.0015 .times. 106 per mL (starting from 50 mL). These direct assays were used in experiments on filtration with three types of filters: the Cellselect B-1005, B-1014 and the B-1013 (bedside filter). After filtration of 1 unit of blood cell suspension through the B-1005, the number of remaining platelets was found to vary between .ltoreq. 0.04 .times. 106 and > 15 .times. 106 per mL (n = 16); after filtration through the B-1013 filter, the remaining platelets were > 0.04 .times. 106 per mL. Upon filtration of a second unit of blood cell suspension through the B-1013 filter, the number of remaining platelets varied between .ltoreq. 0.04 .times. 106 and 5 .times. 106. In both filter types, the number of remaining granulocytes was always > 0.01 .times. 106 per mL. A study of T-lymphocyte contamination revealed that, upon filtration of 1 unit of blood through the B-1005, T-lymphocyte numbers were .ltoreq. 0.0015 .times. 106 to 0.15 .times. 106 per mL (starting from 5 and 50 mL); upon filtration through the B-1013 filter, the number of remaining T lymphocytes varied between .ltoreq. 0.006 .times. 106 and 0.2 .times. 106 per mL (starting from 5 mL). After filtration of a second unit of blood cell suspension through the B-1013 filter, the number or remaining T lymphocytes rnaged from .ltoreq. 0.006 .times. 106 to 0.1 to 0.5 .times. 106 per mL (starting from 5 mL). The direct radioimmunoassay is an improvement over the present electronic particle-counting techniques with regard to both sensitivity and specificity and may therefore be useful in quality control procedures in blood transfusion as well as the in the development of new filters.