Sensitive two-stage papain technique without cell washing

A two-stage papain technique is described in which cell washing after papain treatment is replaced by the addition of a specific papain inhibitor. This technique permits optimal enzyme treatment of red cells while digestion of immunoglobulin following the addition of serum is avoided. The technique therefore combines the design and consequent sensitivity advantage of two-stage tests with the convenience of one-stage tests, rendering it suitable for use in compatibility testing.