Paeds Vivas · professional-practice-and-evidence
Diagnostic accuracy and screening statistics — branching viva
Viva on diagnostic accuracy, likelihood ratios, screening bias and the appraisal of a diagnostic test in child health.
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Target exams
RACP DCEMRCPCH ClinicalRCPSC Pediatrics
Prompt
Journal club: you are given a diagnostic accuracy study claiming a bedside test is 95 percent sensitive and 93 percent specific for a serious paediatric condition; the study recruited from a tertiary referral service, the abstract reports a positive predictive value of 80 percent, and a colleague proposes adopting the test across the community.
Opening (candidate)
I would treat this as a structured appraisal rather than a result handover. First I would judge the study's validity with QUADAS-2 before trusting the headline sensitivity and specificity, then I would ask whether the quoted positive predictive value applies to the community population, and finally I would work out how the test's likelihood ratio moves the probability of disease in an individual child. [9] [4]
References6ShowHide
- [4]Akobeng AK Understanding diagnostic tests 1: sensitivity, specificity and predictive values. Acta paediatrica, 2007.PMID 17407452
- [5]Akobeng AK Understanding diagnostic tests 2: likelihood ratios, pre- and post-test probabilities and their use in clinical practice. Acta paediatrica, 2007.PMID 17306009
- [7]Deeks JJ, Altman DG Diagnostic tests 4: likelihood ratios. BMJ, 2004.PMID 15258077
- [9]Whiting PF, Rutjes AW, Westwood ME, et al. QUADAS-2: a revised tool for the quality assessment of diagnostic accuracy studies. Annals of internal medicine, 2011.PMID 22007046
- [10]Lijmer JG, Mol BW, Heisterkamp S, et al. Empirical evidence of design-related bias in studies of diagnostic tests. JAMA, 1999.PMID 10493205
- [13]Esserman LJ, Thompson IM, Reid B, et al. Addressing overdiagnosis and overtreatment in cancer: a prescription for change. Lancet oncology, 2014.PMID 24807866