Detection of adrenocortical autoantibodies in Addison's disease with a peroxidase-labelled protein A technique

Adrenocortical autoantibodies (ACA), present in 60-80 percent of patients with idiopathic Addison's disease, are conventionally detected by indirect immunofluorescence (IIF) on frozen sections of adrenal glands. The large-scale use of IIF is limited in part by the need for a fluorescence microscope and the fact that histological sections cannot be stored for long periods of time. To circumvent these restrictions we developed a novel peroxidase-labelled protein A (PLPA) technique for the detection of ACA in patients with Addison's disease and compared the results with those obtained with the classical IIF assay. We studied serum samples from 90 healthy control subjects and 22 patients with Addison's disease, who had been clinically classified into two groups: idiopathic (N = 13) and granulomatous (N = 9). ACA-PLPA were detected in 10/22 (45 percent) patients: 9/13 (69 percent) with the idiopathic form and 1/9 (11 percent) with the granulomatous form, whereas ACA-IIF were detected in 11/22 patients (50 percent): 10/13 (77 percent) with the idiopathic form and 1/9 (11 percent) with the granulomatous form. Twelve of the 13 idiopathic addisonians (92 percent) were positive for either ACA-PLPA or ACA-IIF, but only 7 were positive by both methods. In contrast, none of 90 healthy subjects was found to be positive for ACA. Thus, our study shows that the PLPA-based technique is useful, has technical advantages over the IIF method (by not requiring the use of a fluorescence microscope and by permitting section storage for long periods of time). However, since it is only 60 percent concordant with the ACA-IIF method, it should be considered complementary instead of an alternative method to IIF for the detection of ACA in human sera

Detection of Salmonella C1, D and V1 antigens, by coagglutination, in blood cultures from patients with Salmonella infections.

Protein A-containing Staphylococcus aureus was coupled to Salmonella C1, D and Vi monovalent antisera to produce C1-, D- and Vi-COAG reagents. The reagents were used to detect their homologous Salmonella antigens in blood cultures (BC). The D and Vi antigens were detected in 79 of 239 BC from patients with suspected typhoid fever and Salmonella typhi was later isolated from the same 79 BC. The C1 antigen was detected in 8 BC from which only S. oranienburg was later isolated. The COAG test was generally positive at the same time the BC became culture positive. However, because of subculture and biochemical identification requirements the COAG test could be interpreted 1-2 days before culture results were available. The COAG test can be used to presumptively identify Salmonella typhi and Salmonella group C1 in blood cultures before the culture results are available.