Title 



Bayesian clinical reasoning: does intuitive estimation of likelihood ratios on an ordinal scale outperform estimation of sensitivities and specificities?
 
Author 



 
Abstract 



Rationale: Bedside use of Bayes' theorem for estimating probabilities of diseases is cumbersome. An alternative approach based on five categories of powers of tests from 'useless' to 'very strong' has been proposed. The performance of clinicians using it was assessed. Methods Fifty clinicians attending a course of tropical medicine estimated powers of tests and posttest probabilities using the classical vs. the categorical Bayesian approach. The estimation of posttest probability was assessed for real and dummy diseases in order to avoid the bias of previous knowledge. Accuracy of answers was measured by the difference with reference values obtained from an expert system (Kabisa). Results Clinicians estimated positive likelihood ratios (LRs) a median of −1.07 log10 lower than Kabisa [interquartile range (IQR): −1.47; −0.80] when derived classically and −0.17 (IQR: −0.42; +0.04) when estimated categorically (P < 0.001). For negative LRs the median was +0.39 log10 higher (IQR: +0.71; +0.08) when derived classically and −0.18 log10 lower (IQR: +0.03; −0.36) when estimated categorically (P < 0.001). Twenty (40%) disclosed not being able to calculate posttest probabilities using sensitivities and specificities. Regardless the approach posttest probabilities were overestimated both for real and dummy diseases [respectively +1.23 log10 (IQR: +0,67; +2.08) and +2.03 log10 (IQR: +0.49; +2.42)] (P = 0277), but the range was wider for the latter (P = 0.001). Conclusions Participants were more accurate in estimating powers with a categorical approach than with sensitivities and specificities. Posttest probabilities were overestimated with both approaches. Knowledge of the disease did not influence the estimation of posttest probabilities. A categorical approach might be an interesting instructional tool, but the effect of training with this approach needs assessment.   
Language 



English
 
Source (journal) 



Journal of evaluation in clinical practice.  Oxford  
Publication 



Oxford : 2008
 
ISSN 



13561294
 
Volume/pages 



14:5(2008), p. 934940
 
ISI 



000260544400048
 
Full text (Publishers DOI) 


  
