Modification of the platelet suspension immunofluorescence test.

This study reports two modifications of the Platelet Suspension Immunofluorescence Test which make it more convenient to use for the rapid identification of platelet-specific antibodies and for screening individuals if platelet donors of a particular type are urgently required. Platelets frozen both before and after paraformaldehyde (PFA) fixation were compared with fresh PFA-fixed platelets using anti-PLA1 and anti-HLA antisera. Further, a comparison was made between the results of the test when performed in tissue culture trays or in tubes as originally described. Platelets, prefixed with PFA and then frozen appeared similar in all respects to fresh PFA-fixed platelets with no loss of antigenicity and no non-specific fluorescence. Although platelets fixed after frozen storage were also satisfactory, they were less convenient to use and lost some brilliance in staining. When the test was performed in tissue culture trays, there was no loss in sensitivity, and the volume of antiserum used was halved. However, the main advantage was the efficiency and ease with which the test could be performed, especially when handling large numbers of samples.