Critical appraisal of diagnostic article
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Critical appraisal of diagnostic article

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Critical appraisal of diagnostic article Critical appraisal of diagnostic article Presentation Transcript

  • CRITICAL APPRAISAL OF ARTICLES ABOUT DIAGNOSTIC TEST Dr. Faisal Al Haddad Consultant of Family Medicine & Occupational Health Incharge of Occupational Health Unit PSMMC
  • Process of EBM  Ask  Acquire  Appraise  Apply
  • (Critical Appraisal (Diagnosis  Are the results valid?  What  Will are the results? the results help me in caring for my patients?
  • ?I Are the results valid
  • Was there an independent, blind. 1 ?comparison with a reference standard  Is reference standard used acceptable?  Were the investigators interpreting a test blinded to the results of the other test?
  • Did the patient sample include an appropriate. 2 spectrum of patients to whom the diagnostic ?test will be applied in clinical practice  Representative of the patients in whom the test is to be used.  Varying  Varying  Varying presentations of the target disorder severity of the target disorder stage of the target disorder
  • 3. Did the results of the test being evaluated influence the decision to perform the reference standard?  Was the gold standard applied to subjects in whom the study investigation was negative?  Were both reference standard and test under investigation applied to all patients?
  • Were the methods for performing .4 the test described in sufficient detail ?to permit replication  Preparation of patient?  Performance  Analysis of test? and interpretation of results?
  • ?II What are the Results  
  • What is Likelihood Ratio            NLR: Ratio of the probability of a false negative result if the disease is present to a true negative result if the disease is absent. FN/TN The extent to which a negative test decreases the likelihood that a patient has disease The less the NLR, the less the likelihood that a patient with negative test has disease e.g. CT scan with NLR of 0.05 -ve CT scan indicates that the pat is free from PE PLR: Ratio of the probability of a true positive result if the disease is present to a false positive result if the disease is absent. TP/FP The extent to which a positive test increases the likelihood that a patient has disease. The more the PLR, the more the likelihood that a patient with positive test has disease e.g. CT scan with PLR of 20 +ve CT scan indicates that the pat has PE
  • III Will the results help me in ?caring for my patients
  • 1. Will the reproducibility of the test result and its interpretation be satisfactory in my clinical setting?
  • Are the results applicable to the. 2 ?patient in my practice  Similar distribution of disease severity?  Similar distribution of competing diseases?  Does the patient meet the study inclusion criteria?  Does the patient violate any of exclusion criteria?
  • Will the results change my management. 3 ?strategy Are the test LRs high or low enough to shift post-test probability across a test or treatment threshold?
  • Pulmonary embolism management:  Treatment threshold 80%  Test threshold 10% VQ scan properties:  PLR 20  NLR 0.36   78-year-old woman chest pain and shortness of breath 10 days after surgery  Pretest probability of pulmonary embolism 70%.  Posttest probability with abnormal VQ scan result 97%  Posttest probability with normal VQ scan result 19% 28-year-old man chest pain and shortness of breath experiencing a high level of anxiety.  Pretest probability of pulmonary embolism 20%  Posttest probability with abnormal scan result is 85%  Posttest probability with normal VQ scan result is 2%
  • Will patients be better off as a. 4 ?result of the test    Is target disorder dangerous if left undiagnosed?  Is test risk acceptable?  Does effective treatment exist?
  • THANK YOU
  • ANY ?QUESTIONS