Quantification of islet cell antibodies by microscope photometry and antibody titration compared

Islet cell antibodies can predict eventual insulin-dependent diabetes mellitus. In the standard method used by the Immunology of Diabetes Workshop (IDW), predictive power depends on antibody titer as determined by testing multiple serum dilutions. Here I report use of a microscope-based photometry system (MPS) to test whether islet fluorescence intensities from undiluted sera can predict IDW results. MPS testing of 120 undiluted IDW specimens correctly identified 27 of 31 positive and 84 of 89 negative specimens. The relationship between IDW consensus values and MPS readings of undiluted sera is: IDW = 2.45 MPS - 1.44 (r = 0.67, P less than 0.001). Thus, corrected islet intensities from undiluted sera correlated well with IDW values. However, the ability of MPS to predict high IDW consensus values is limited, which may reflect the variable antigenic content of pancreas specimens; moreover, background correction as currently applied is incomplete; nonspecific immunofluorescence appears to emanate from within the islet.