Critical Appraisal Quiz!

Critical Appraisal Quiz! P(There will be prizes) <0.05

Which one of the following best describes absolute risk increase? • Control event rate (CER) – experimental event rate (EER) • CER + EER • EER – CER • The likelihood of a positive result • The proportion of positives accurately diagnosed with a disorder C

Which of the following best describes the term external validity? • The agreement between two raters using the same test at the same time • The consistency of a measure used on two separate occasions • The extent to which one can appropriately apply the results to other populations • The level of agreement between two or more raters using the same test on two or more occasions • The level of consistency between two separate halves of the same test C

Which of the following describes a cohort study? Longitudinal; case-control; controlled trial; cross-sectional • A study that aims to establish the normal height of 4yr old children by measuring height as school entry • A study that compares a group of children who’s heights are below the tenth centile with a group of matched controls of normal height aiming to identify possible causative factors • A study that compares two groups of 4yr olds with similar characteristics: one group is given a drug and the other a placebo and the growth of each group is measured following this intervention • A study that compares the height of a group of 4yr olds living near a nuclear plant with the height of a group of 4yr olds who live elsewhere • A study that looks a all children born at one hospital in one year and measures their height at intervals up to four years of age Cross-sectional Case-control Cohort Controlled Trial Longitudinal

A hierarchy of quality in evidence based medicine exists, with study types ranked according to the strength of their data Case report (CR) Randomised double-blind placebo controlled trial (RCT) Case-control study (CC) Meta-analysis (MA) Which one of the following correctly ranks the study types with the most robust first and the least robust last? • RCT, CR, CC, MA • MA, RCT, CC, CR • RCT, CR, MA, CC • CR, CC, MA, RCT • RCT, CC, MA, CR B

EMQ – Study types The Framington Heart study The Cochrane Collaboration The Scandinavian Simvastatin Survival Study A trial of sham acupuncture for period pains in which patients are allocated randomly to treatment or placebo A study of patient’s experiences of berevement • Case-control • Case report • Cohort Study • Double-blind, randomised, placebo-controlled trial • Meta-analysis • Qualitative Study • Single-blinded, randomised, placebo-controlled trial

A new test to screen for CF carriers is being considered. Preliminary results for the test in 100 children, in comparison with the gold standard of chromosome analysis, are shown below • The accuracy of the test is 91% • The new test is better than the GS • Positive predictive value is 80% • The sensitivity is 80% • The specificity is 87% T F F T F

That last slide explained… • Accuracy – proportion of tests with correct results = a+d/a+b+c+d = 91/100 = 91% • Sensetivity – the true positive rate = a/a+c = 4/5 = 80% • Specificity – the true negative rate = d/b+d = 87/95 = 92% • Positive predictive value – the probability of having the condition once test is +ve = a/a+b = 4/12 = 33% • Negative predictive value – probability of having condition once test is –ve = d/c+d = 87/88 = 99%

A trial is conducted to determine which symptoms and signs have the most impact on the diagnosis of pneumonia in patients with resp symptoms in primary care. Results are presented below: T F F T F • Abnormal chest exam increases probability of pneumonia by 25% • Tachypnoea has a negative association with diagnosis of pnuemonia • The presence of cough increases probability of pneumonia by 100% • The presence of fever makes the diagnosis of pneumonia less likely • These results allow the diagnosis to be made without examining the patient

Critical Appraisal Quiz!