
TY  - JOUR
A1  - Arroll, Bruce 
A1  - Allan, GM 
A1  - Raina Elley, C 
A1  - Kenealy, Tim 
A1  - McCormack, James 
A1  - Hudson, Ben 
A1  - Hoare, Karen 
T1  - Viewpoint: Diagnosis in primary care: probabilistic reasoning
JF  - Journal of Primary Health Care
JO  - J Prim Health Care
Y1  - 2012
VL  - 4
IS  - 2
SP  - 166
EP  - 173
KW  - 
UR  - https://doi.org/10.1071/HC12166 
N2  - This article develops the concept of probabilistic reasoning as one of the techniques clinicians use in making a diagnosis. We develop the concept that every question and every examination is a diagnostic test ultimately leading to a rule in or rule out of a diagnosis. We also develop the concept of pre-test probability pointing out that false positive tests are an issue in low-prevalence settings and false negative tests are a problem. Investigative tests work best in medium-prevalence settings. The purpose of taking a history and conducting an examination is to increase the pre-test probability to a point where either treatment is commenced or more expensive/time-consuming/dangerous tests are indicated. Pre-test probabilities on their own can be used to rule out conditions. We also show how pre-test probabilities relate to the Fagan nomogram which enables visualisation of large changes in post-test probabilities which can lead to treatment/further investigation. KEYWORDS: Likelihood ratio; pre-test and post-test probability; diagnostic accuracy; probabilistic reasoning 
ER  -

