A Guide to Handling Missing Data in Cost-Effectiveness Analysis Conducted Within Randomised Controlled Trials

The authors would like to thank Professor Adrian Grant and the team at the University of Aberdeen (Professor Craig Ramsay, Janice Cruden, Charles Boachie, Professor Marion Campbell and Seonaidh Cotton) who kindly allowed the REFLUX dataset to be used for this work, and Eldon Spackman for kindly sharing the Stata (R) code for calculating the probability that an intervention is cost effective following MI. The authors are grateful to the reviewers for their comments, which greatly improved this paper. M. G. is recipient of a Medical Research Council Early Career Fellowship in Economics of Health (grant number: MR/K02177X/1). I. R. W. was supported by the Medical Research Council [Unit Programme U105260558]. No specific funding was obtained to produce this paper. The authors declare no conflicts of interest.Missing data are a frequent problem in cost-effectiveness analysis (CEA) within a randomised controlled trial. Inappropriate methods to handle missing data can lead to misleading results and ultimately can affect the decision of whether an intervention is good value for money. This article provides practical guidance on how to handle missing data in within-trial CEAs following a principled approach: (i) the analysis should be based on a plausible assumption for the missing data mechanism, i.e. whether the probability that data are missing is independent of or dependent on the observed and/or unobserved values; (ii) the method chosen for the base-case should fit with the assumed mechanism; and (iii) sensitivity analysis should be conducted to explore to what extent the results change with the assumption made. This approach is implemented in three stages, which are described in detail: (1) descriptive analysis to inform the assumption on the missing data mechanism; (2) how to choose between alternative methods given their underlying assumptions; and (3) methods for sensitivity analysis. The case study illustrates how to apply this approach in practice, including software code. The article concludes with recommendations for practice and suggestions for future research.Medical Research Council Early Career Fellowship in Economics of Health MR/K02177X/1Medical Research Council UK (MRC) U105260558Medical Research Council UK (MRC) MC_U105260558 MR/K02177X/

Silk garments plus standard care compared with standard care for treating eczema in children: a randomised controlled, observer blind, pragmatic trial (CLOTHES Trial)

Background The role of clothing in the management of eczema (syn. atopic dermatitis, atopic eczema) is poorly understood. This trial evaluated the effectiveness and cost-effectiveness of silk garments (in addition to standard care) for the management of eczema in children with moderate to severe disease. Methods and findings This was a parallel group randomised controlled, observer-blind trial. Children aged 1 to 15 years with moderate to severe eczema were recruited from secondary care and the community in five UK centres. Participants were allocated using on-line randomisation (1:1) to standard care, or standard care plus silk garments; stratified by age and recruiting centre. Silk garments were worn for 6 months. Primary outcome (eczema severity) was assessed at baseline, 2, 4 and 6 months, by nurses blinded to treatment allocation using the Eczema Area and Severity Index (EASI), which was log-transformed for analysis (intention-to-treat analysis). Safety outcome: number of skin infections. Three hundred children were randomised (26th Nov 2013 to 5th May 2015): 42% girls, 79% white, mean age 5 years. Primary analysis included 282/300 (94%) children (n = 141 in each group). The garments were worn more often at night than in the day (median of 81% of nights (25th to 75th centile 57% to 96%) and 34% of days (25th to 75th centile 10% to 76%)). Geometric mean EASI scores at baseline, 2, 4 and 6 months were 9·2, 6·4, 5·8, 5·4 for silk clothing and 8·4, 6·6, 6·0, 5·4 for standard care. There was no evidence of any difference between the groups in EASI score averaged over all follow up visits adjusted for baseline EASI score, age and centre (adjusted ratio of geometric means: 0·95, 95% CI 0·85 to 1·07). This confidence interval is equivalent to a difference of -1·5 to 0·5 in the original EASI scale units which is not clinically important. Skin infections occurred in 36/142 (25%) and 39/141 (28%) for silk clothing and standard care respectively. Even if the small observed treatment effect was genuine, the incremental cost per QALY was £56,881 in the base case analysis from an NHS perspective, suggesting that silk garments are unlikely to be cost-effective within currently accepted thresholds. Main limitations: whilst minimising detection bias, use of an objective primary outcome may have underestimated treatment effects. Conclusions Silk clothing is unlikely to provide additional benefit over standard care in children with moderate to severe eczema