1 / 10

Analyzing Randomized Control Trial: ITT vs. PP vs. AT Proceedings from Journal club…..

Analyzing Randomized Control Trial: ITT vs. PP vs. AT Proceedings from Journal club…. Vikash. Basic Analysis of RCT:. To calculate: Relative Risk (RR) Relative Risk Ratio (RRR) Attributable Risk (AR) Absolute Risk Reduction (ARR) Number Needed to treat (NNT)

Download Presentation

Analyzing Randomized Control Trial: ITT vs. PP vs. AT Proceedings from Journal club…..

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Analyzing Randomized Control Trial: ITT vs. PP vs. ATProceedings from Journal club….. Vikash

  2. Basic Analysis of RCT: • To calculate: • Relative Risk (RR) • Relative Risk Ratio (RRR) • Attributable Risk (AR) • Absolute Risk Reduction (ARR) • Number Needed to treat (NNT) • For Time dependant analysis • Survival Analysis by Kaplan- Mier or by Cox Proportional Model. • Then, Apply test of Significance.

  3. For Dichotomous Outcome: • RR = ID (Exposed)/ ID (Unexposed) = a/a +b / c /c +D • RRR = 1 – RR • ARR = ID (Unexposed) - ID (Exposed)

  4. Attributable Risk = (OR – 1) PE / 1+ [ (OR-1) PE] x 100 • Where OR = Odds Ratio = ad / bc • Number Needed to treat (NNT) = 1/ARR • RR = 0. 4 /0.5 = 0.8 • RRR = 0.2 • ARR = 0.2 – 0.25 = - 0.05 • NNT = 1/ARR = 20

  5. Intention to treat Analysis • Also called As randomized or Method Effectiveness analysis. • Compare outcome according to the randomized group (Gold Standard). • Adherence to intervention not necessary. Advantages: • Randomization is maintained: • Treatment assignment is based on chance alone. • Randomization provides Theoretical foundation for Statistical test of significance. Disadvantages: • Doesn’t take into account Protocol violation.

  6. Group may not be comparable at the end. • Not adhering to treatment or vice versa. • Eligibility for the trial was incorrect. • Loss to follow up. • Estimates of non – complied in the efficacy dilutes difference between groups. • Analysis may underestimate adverse effect. Why gold standard ? • Randomization is maintained • Difficulty in defining compliance. • Effect in complied group may be due to factor of compliance.

  7. Per Protocol Analysis: • Analyze only those who fully complied to protocol. • Doesn’t included cross- over in final analysis. • Provides fair idea of efficacy for treatment. • May be Biased (randomization compromised) As treated Analysis: • Subject analyzed according to treatment taken or not. (no relation with randomization). • Non compliant from treatment and vice versa analyzed accordingly. • AT is shown if ITT shows no effect ( why trial done).

  8. Hypothetical Example: RCT to see the effect of Aspirin in incidence of Myocardial Re-infarction in patient with h/o MI. • ARR by ITT = 20.833% - 16.66% = 4.17% • ARR by PP = 23% - 16.66% = 6.34% • ARR by AT = 21.25% - 16.25% = 5%

  9. References: • Redmond C, Armitage P editors. Biostatics in Clinical Trials. 1st ed. Sussex. John Wiley & Sons ltd. 2001. p243- 6. • Haynes RB, Sacket DL, Guyat GH, Tugwell P. Clinical Epidemiology. 3rd ed. Baltimore. Lippincott Williams & Wilkins.2006. p 95 & 116. • Fletcher RW, Fletcher SW. Clinical Epidemiology: the essential. 4th ed. Baltimore. Lippincott Williams & Wilkins. 2005. p 136-9.

More Related