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Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn

Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn. Indices of Performances of CPRs Nicola Motterlini, Borislav D Dimitrov, Tom Fahey. Contents. CPR derivation Analytical approach CPR validation Indices of discrimination Indices of calibration

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Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn

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  1. Royal College of Surgeons in IrelandColáiste Ríoga na Máinleá in Éirinn Indices of Performances of CPRs Nicola Motterlini, Borislav D Dimitrov, Tom Fahey

  2. Contents • CPR derivation • Analytical approach • CPR validation • Indices of discrimination • Indices of calibration • Performance of a CPR in several validation studies (systematic review with meta-analysis)

  3. Stages of development of a CPR

  4. Analytical approachto CPR(an example) Target disorder (presence or absence) Multivariable approach (e.g., logistic regression model) Total score: 3+2+1 = 6 Prediction LOW RISK % Total score ≤ 3 MODERATE RISK % 4 ≤ Total score ≤ 7 HIGH RISK % Total score ≥ 8 Decision NO TREATMENT FURTHER DIAGNOSTIC TESTING TREATMENT

  5. Thresholds approach to diagnosis Score 100% HIGH RISK Treatment 10 9 8 7 6 5 4 3 2 1 Diagnosis / test threshold Probability of disease Further diagnostic testing Test / reassurance threshold 0% LOW RISK No treatment

  6. Stages of development of a CPR

  7. Performance of a CPR can be assessed like a performance of a diagnostic test! TP, number of true positives, FP, number of false positives, FN, number of false negatives, TN, number of true negatives, NT+, the number of patients with positive test results, NT-, the number of patients with negative test results, ND+, the number of patients with the disease, and ND−, number of patients without the disease

  8. Indices of performance • For discrimination (classification) • Ability to discriminate between diseased individuals and non-diseased individuals (e.g., sensitivity, specificity, ROC curve, odds ratio, positive and negative predictive values, likelihood ratio etc.) • For calibration (comparison) • Agreement between predicted probabilities and observed probabilities (e.g., risk ratio, Hosmer-Lemeshow goodness-of-fit test etc.)

  9. Discrimination – sensitivity and specificity Sensitivity = TP/ND+ Specificity = TN/ND-

  10. Calibration – risk ratio Predicted Disease risk (%) Observed Low Moderate High Score risk <1 “under-prediction” =1 “accurate prediction” >1 “over-prediction” Predicted Risk ratio -> Observed

  11. Performance of a CPR in several validation studies (systematic review with meta-analysis)

  12. Pooled analysis • When the 95% CI includes 1 there is no significant statistical difference between the observed and predicted by CPR • The smaller the interval, the more accuracy are the results

  13. Index of heterogeneity I2 value over 50% is a strong indicator for heterogeneity

  14. Summary • CPR derivation • Multivariable approach to develop a CPR • CPR validation • Indices of discrimination (sensitivity, specificity) • Indices of calibration (risk ratio) • Systematic review with meta-analysis of validation studies of CPRs

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