The aim of the study was to evaluate the diagnostic value and performance of a new IIF test to detect antibodies against BP180 and BP230 in relation to the ELISA method. Specifically, ELISA has many advantages: it is a minimally invasive technique, it allows performing the analysis of multiple samples simultaneously and in a limited time, it is an easily reproducible method, and it provides a quantitative analysis [11
]. A limitation of the ELISA method is that the recombinant proteins used may not contain all of the epitopes present in vivo. A final disadvantage is the high cost of the method.
The BIOCHIP technique has proved to be a specific and sensitive diagnostic alternative to the ELISA diagnosis of BP [10
]. A BIOCHIP mosaic, prepared using different tissue sections, cell substrates or antigenic molecules, requires only a simple antibody incubation to obtain a detailed profile, so it is possible to search simultaneously different antibodies directed against different organs or infectious agents. Some of the advantages of the BIOCHIP technology include the possibility to analyse simultaneously several serum samples, the short time necessary for performing test (about 100 minutes), the easy interpretation of results which are interpreted visually and does not require spectrophotometric equipment, making it possible also in small laboratories. Furthermore all incubation steps proceed at room temperature and there is low reagent consumption: only 50μ
L each of diluted serum and reagent are needed per test field. Finally, unlike ELISA, in which we have specific kits for a single parameter, with this new IIF based test, there may be more parameters in a single session using only one kit. Therefore the BIOCHIP method is fairly cheap compared to the ELISA methods although we have not yet made a detailed cost analysis. The main disadvantage of BIOCHIP technique against ELISA is the fact that it does not provide a quantitative value.
Although our study was based on a relatively small group of patients, our results were comparable with previous investigations [10
]. Taken together, these cumulative findings indicate that, in the determination of autoantibodies to BP180, the diagnostic specificity of the BIOCHIP method was almost comparable to the ELISA [10
], whereas in the detection of anti-BP230-gC the diagnostic sensibility for BP230 was slightly reduced [10
]. These data indicate that BIOCHIP method may replace the classical IIF, which can be considered outdated in some ways. Using several BIOCHIPs coated with different substrates side by side on one and the same reaction field, antibodies against different skin target structures can be investigated simultaneously, notably BP180, BP230, DSG1, and DSG3. Therefore, this new immunoassay can be used as an excellent screening test for patients with suspected autoimmune bullous skin disease, preserving the more expensive ELISA test in doubtful cases.
In conclusion, the novel BIOCHIP described here is a flexible, specific, and sensitive alternative to detect autoantibodies by IIF and ELISA in the diagnostic workup of BP. This new method can not only be applied to the diagnosis and screening of BP, but also enrich the serological diagnosis of other autoimmune diseases by additional parameters. The BIOCHIP technology proved to be a valuable complementary diagnostic tool, for the simplicity of execution, low cost, and high sensitivity.