Abstract: A method is provided for qualitatively detecting in vitro the presence or absence of selected circulating antibody types using a diagnostic kit comprising reconstituted, after lyophilization or evaporative drying, red blood cell samples or other cell or cell-like material which have antigens which are recognized and bound by the selected antibody-type to be screened. Diagnostic kits containing the lyophilized blood samples according to the present invention have improved shelf life, and may comprise lyophilized samples packaged in a variety of forms convenient for manual single-test uses or automated multiple-test uses.