Question

Intent- to- treat analysis shows no significant difference in outcome between intervention and control groups in a randomized clinical trial, using a simple 2x2 table. You have recorded the occurrence and time of events (outcome) and loss to follow up. You notice that 40% in each group were lost to follow up over the 3 years of trial duration. A) Discuss the potential impact of loss to follow-up on the results of your trial. B) What other analysis can you perform?   

Answer 1

Ans.) In Random controlled trials (RCT) often suffer from two major complications, i.e., noncompliance and missing outcomes. One possible solution to this problem is a intention-to-treat (ITT) analysis. ITT analysis includes every subject which is randomized according to randomized treatment assignment. It overlooks noncompliance, protocol deviations, withdrawal, and anything that occurs after randomization. ITT analysis maintains analytical balance that is generated from the original random treatment allotment. In ITT analysis, estimate of treatment effect is mostly conservative. Always try to minimize the missing responses and to continue to follow up those who withdraw from treatment.

To calculate the loss to follow-up one can do it by determining the right denominator. That includes all those which are randomly assigned in an RCT, and all who had the procedure during a prespecified time in a retrospective cohort study.

• A good rule of thumb is that <5% loss leads to little bias, while >20% poses serious threats to validity. However, even less than 20% loss to follow-up can be a problem.
• Consider a worst-case scenario which help to determine whether loss to follow-up poses a potential threat to validity.
• Loss to follow-up in randomized controlled trials could bias results if the unavailability of data is associated with the likelihood of outcome events.

It hugely affects the outcomes of patients lost to follow-up because it could change the interpretation of results of randomized controlled trials