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

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

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

Which of the following describes a cohort study? A.A study that aims to establish the normal height of 4yr old children by measuring height as school entry B.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 C.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 D.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 E.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 Longitudinal; case-control; controlled trial; cross-sectional

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

EMQ – Study types A.Case-control B.Case report C.Cohort Study D.Double-blind, randomised, placebo-controlled trial E.Meta-analysis F.Qualitative Study G.Single-blinded, randomised, placebo-controlled trial 1.The Framington Heart study 2.The Cochrane Collaboration 3.The Scandinavian Simvastatin Survival Study 4.A trial of sham acupuncture for period pains in which patients are allocated randomly to treatment or placebo 5.A study of patient’s experiences of berevement

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 A.The accuracy of the test is 91% B.The new test is better than the GS C.Positive predictive value is 80% D.The sensitivity is 80% E.The specificity is 87% positive chromosome analysis negative chromosome analysis New test positive48 New test negative187 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% positive chromosome analysis negative chromosome analysis New test positive4 (a)8 (b) New test negative1 (c)87 (d)

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: Symptom/SignLikelihood Ratio for diagnosis Fever0.94 Cough1.00 Abnormal chest examination1.25 Tachyponoea1.34 Otalgia0.07 A.Abnormal chest exam increases probability of pneumonia by 25% B.Tachypnoea has a negative association with diagnosis of pnuemonia C.The presence of cough increases probability of pneumonia by 100% D.The presence of fever makes the diagnosis of pneumonia less likely E.These results allow the diagnosis to be made without examining the patient T F F T F