LOSS TO FOLLOW-UP MATTERS

Survival analysis of joint replacement relies on the assumption that s urgical procedures in patients lost to follow-up have the same chance of failing as those in patients who continue:to be assessed, Our study questions that assumption. During the 16-year follow-up of 2268 patie nts who had received total hip replacements 142 (6%) were lost to foll ow-up, The cumulative loss at 15 years was 20%, At their last assessme nt, patients who subsequently failed to attend for follow-up had signi ficantly worse pain, range of movement and opinion of their progress ( p < 0.001) and significantly worse radiological features than a matche d control group (p < 0.01). Patients lost to follow-up have a worse ou tcome than those who continue to be assessed. Consequently, a survival analysis that does not take into account such patients is likely to g ive falsely optimistic results, It is therefore essential that vigorou s attempts are made to minimise loss to follow-up, and that the rate o f such loss is quoted, The overall loss to follow-up disguises the mag nitude of the problem, which is best quantified by a cumulative rate o f follow-up. The reliability of a study can be assessed by a loss-to-f ollow-up quotient, calculated by the number of failures: the lower the quotient the more reliable the data. Ideally, the quotient should be less than 1.