Detection of HLA antibodies by an enzyme-linked photometric immune phagocytosis inhibition test

The immune phagocytosis inhibition test (IPI) has been described as a sensitive method for the detection of cytotoxic and non-cytotoxic HLA antibodies. We performed a photometric IPI and compared this technique with the conventional microscopic IPI. In further investigations we used the photometric IPI in comparison with the lymphocytotoxicity test (LCT) for the detection of HLA antibodies. The photometric IPI showed a high correlation to the microscopic IPI. In tests with different known HLA antibodies the photometric IPI reached a sensitivity of 85.1% versus 80.5% in the LCT, and a specificity of 92.3 versus 100% in the LCT. Diluted patient sera showed a higher sensitivity in the photometric IPI. We conclude that the photometric IPI can be used as a convenient and sensitive technique for the detection of HLA antibodies.