The clinical significance of serological methods in the diagnosis of staphylococcal septicaemia and endocarditis.

In comparison to healthy controls we have found that patients with endocarditis and septicaemia caused by Staphylococcus aureus show significantly higher antibody levels against either S. aureus peptidoglycan, crude staphylococcal antigen or alpha-toxin. The serological methods used in these studies were radio-immunoassays. These results have now been further evaluated concerning their clinical significance. The occurrence rate of S. aureus endocarditis and septicaemia at the clinic was 0.36% and 2.0%, respectively, during the study period. In spite of relatively high levels of test specificities, 93.8-96.9%, the predictive values for positive test results were low, 2.7-23.2%. Using the PG-assay, satisfactory predictive values of 100% together with a sensitivity of 95.2% could nevertheless be reached in the screening for S. aureus endocarditis, if the upper normal limit was raised.