Intent-to-Randomize Corrections for Missing Data Resulting from Run-In Selection Bias in Clinical Trials for Chronic Conditions
National Cancer Institute, Bethesda, Maryland, USA.Journal of Biopharmaceutical Statistics (Impact Factor: 0.59). 03/2011; 21(2):263-70. DOI: 10.1080/10543406.2011.550107
In many clinical trials for chronic conditions a run-in period is used prior to randomization. Often, only those participants who meet certain criteria during the run-in phase go on to get randomized. The others, along with the information that they might have provided, are excluded from the study. This exclusion of the relevant response data from any subsequent study analysis can be considered as resulting in missing data; although quite common in practice, this approach has expectedly been shown to create a bias in favor of the active treatment when this active treatment is used during the run-in. Hence, many randomized clinical trials report overly optimistic results, with the extent of the bias depending in large part on how many otherwise eligible subjects were excluded due to the use of the run-in. If these biased trials are to contribute valid information to medical decision making, then the biases need to be corrected, and this involves accounting for all participants who were intended to be randomized. We propose specific imputation methods for doing so.
Article: Intent-to-treat: further insightResearch in Nursing & Health 02/2011; 34(1):4; author reply 5-6. DOI:10.1002/nur.20405 · 1.27 Impact Factor
- Contemporary clinical trials 01/2012; 33(1):12. DOI:10.1016/j.cct.2011.09.014 · 1.94 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Although it is generally acknowledged that electronic monitoring of adherence to treatment improves blood pressure (BP) control by increasing patients' awareness to their treatment, little information is available on the long-term effect of this intervention. In this observational study among a total of 470 patients with mild-to-moderate hypertension, adherence was measured in 228 patients by means of both the Medication Event Monitoring System (MEMS) and pill count (intervention group), and in 242 patients by means of pill count alone (control group). During a follow-up period of 1 year consisting of seven visits to the physician's office, BP measurements were performed and medication adjusted based on the achieved BP. In addition, at each visit adherence to treatment was assessed. On the basis of pill counts, median adherence to treatment did not differ between the intervention group and the control group (96.1% vs. 94.2%; P = 0.97). In both groups, systolic and diastolic BP decreased similarly: 23/13 vs. 22/12 mm Hg in the intervention and control group respectively. Drug changes and the number of drugs used were associated with BP at the start of study, but not with electronic monitoring. In this study, electronic monitoring of adherence to treatment by means of MEMS did not lead to better long-term BP control nor did it result in less drug changes and drug use.American Journal of Hypertension 01/2012; 25(1):54-9. DOI:10.1038/ajh.2011.153 · 2.85 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.