A review of randomized controlled trials (RCTs) in four leading medical journals has revealed that the majority of studies did not use imputation to deal with missing quality of life (QoL) outcome data. The results of this study, conducted at the University of Aberdeen, were published this week in Trials, a BioMed Central journal.

Quality of life outcomes are becoming an increasingly important factor for decision-making in clinical trials of new treatments. Often these outcomes are collected via postal questionnaires and consequently subject to a substantial proportion of missing information. Imputation, whereby a reasonable alternative value is substituted for one that is missing, is one of a range of methods used by researchers to account for missing QoL data and thus try to eliminate potential bias in the results.

Fielding et al. conducted a PubMed search to identify a random selection of 285 RCTs published during 2005 and 2006 in the BMJ, The Lancet, The New England Journal of Medicine and the Journal of the American Medical Association. A QoL outcome was reported in 61 papers, which formed the basis of the review. Nineteen (31%) of these trials employed an imputation method to address missing data. Last value carried forward (LVCF) was a popular imputation strategy, although the rationale behind the choice of method was not discussed by any of the articles. A complete-case analysis, whereby the missing data is completely ignored, was undertaken in the majority of studies that did not adopt some form of imputation.

Research
   
A review of RCTs in four medical journals to assess the use of imputation to overcome missing data in quality of life outcomes
Shona Fielding, Graeme Maclennan, Jonathan A Cook, Craig R Ramsay
Trials 2008, 9:51 (11 August 2008)
[Abstract] [Provisional PDF]

The authors highlight the need for avoiding missing data from the outset, clearer reporting and explanation of the methods used to overcome missing data, and discussion of the potential impact of this absent data on results. They conclude that missing data should be more reliably accounted for when analysing QoL outcomes in RCTs.

Trials encompasses all aspects of the design, performance and findings of RCTs in any discipline related to health care. This broad scope includes secondary analyses, information relating trial design and discussion of the challenges face or ‘lessons learned’ in conducting trials. The journal also considers articles about the methodology of trials in general and critical commentaries of trial results published elsewhere. Traditional trial reports are also welcome, regardless of the outcome or significance of the findings. For more information please contact the editorial office.

Abigail Jones
Assistant Editor – Trials