Antibody Assay for Adenoviruses and Mycoplasma pneumoniae by the Platelet Aggregation Test

The practicability of the platelet aggregation test (PAT) in routine antibody assays for adenoviruses and Mycoplasma pneumoniae is demonstrated. An increase in reliability and sensitivity was achieved by employment of EDTA for washing the platelets and by addition of albumin to the test medium. Various lots of platelets yielded reproducible PAT titres which attained 1 : 156,250 in positive patients' sera. Commercially available antigens assigned for complement-fixation (CF) tests proved to be appropriate for the PAT. Checkerboard titrations revealed that the platelet reactivity of immune complexes formed was maintained in a range of up to 625-fold alterations of the antibody: antigen ratio. The fact that PAT and CF titres did not always correlate is interpreted as being due to the differences between complement-fixing and platelet reactivities of various immunoglobulin classes.