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Illustration of pretest and posttest probability. Posttest probability (predictive value) for systemic lupus erythematosus as a function of pretest probability and as a function of indirect immunofluorescence (IIF) and solid phase assay (SPA) (EliA CTD screen, Thermo Fisher) test result. Values for likelihood ratios are from Bossuyt and Fieuws [31], WBC = white blood cell.
