Novel liposome composition for a rapid colorimetric test for systemic lupus erythematosus.

This test for systemic lupus erythematosus utilizes a novel liposome composition entrapping the cation-responsive red dye Arsenazo III. In dilutions of normal sera the liposome membranes undergo a rearrangement when divalent cations are added, resulting in the release of the encapsulated dye and the rapid formation of a stable blue cation-dye complex. Microliter amounts of sera from patients with active lupus stabilize the liposome preparation such that the vesicles remain intact in the presence of the added divalent cations and thus maintain their red color for extended periods. The assay requires 1-min incubations in sera at room temperature and can be performed with standard microtiter plates, allowing the screening of large numbers of serum samples in a short time. Moreover, the unique absorption spectra of the complexed and uncomplexed dye allow for quantification of results.