------------------------------------------------------------------------------- help forfagani-------------------------------------------------------------------------------

Fagan's bayesian nomogram

fagan#prev#lrp#lrn[,options]where

#previs the prior or pretest probability of disease#lrpis the likelihood ratio of a positive test result#lrnthe likelihood ratio of a negative test result

Description

faganicreates a plot showing the relationship between the prior probability, the LR (combination of sensitivity and specificity), and the posterior probability.

RemarksIt is an immediate command, see help immed. When Bayes theorem is expressed in terms of log-odds, the posterior log-odds are a linear function of the prior log-odds and the log likelihood ratio.

faganplots an axis on the left with the prior log-odds, an axis in the middle representing the log likelihood ratio and an axis on the right representing the posterior log-odds. Lines are drawn from the prior probability on the left through the LRs in the center and extended to the respective posterior probability on the right.

Options

legendopts(#)specify options that affect the plot legend.ysize()andxsize()specify the height and width of plot respectively.

Example. fagani 0.5 14.4 0.25

. fagani 0.25 20 0.05, ysize(8) xsize(6)

. fagani 0.45 6.4 0.25, scheme(s2mono)

AuthorBen Adarkwa Dwamena, Division of Nuclear Medicine, Department of Radiology, University of Michigan Medical School, Ann Arbor, Michigan.