RT Journal Article SR Electronic T1 The ‘double whammy’ of low prevalence in clinical risk prediction JF BMJ Evidence-Based Medicine JO BMJ EBM FD BMJ Publishing Group Ltd SP bmjebm-2021-111683 DO 10.1136/bmjebm-2021-111683 A1 Thomas R Fanshawe A1 Seena Fazel YR 2021 UL http://ebm.bmj.com/content/early/2021/08/12/bmjebm-2021-111683.abstract AB