Difference and ratio plots: simple tools for improved presentation and interpretation of scientific data. Unexpected possibilities for the use of the conglutinin binding assay in inflammatory rheumatic diseases.

11111onglutinin-binding assay (KgBa) has gained widespread use for the detection of circulating immune complexes. A recent paper questioned the interpretation of the results obtained by this method and the validity of the assay (Holmskov et al. (1992) J. Immunol. Methods 148, 225). We now present hitherto unnoted differences between controls and patients with either rheumatoid arthritis or systemic lupus erythematosus. For this we use simple, but unconventional, graphic representations of the data, based on difference plots and ratio plots. Differences between patients with Burkitt's lymphoma and systemic lupus erythematosus from another previously published study (Macanovic, M. and Lachmann, P.J. (1979) Clin. Exp. Immunol. 38, 274) are also represented using ratio plots. Our observations indicate that analysis by regression analysis may often be misleading.