Self-monitoring of lower leg skin temperature: accuracy of self-reported data and adherence to a cooling protocol for the prevention of venous leg ulcers

BACKGROUND For intervention studies that require the use of participant self-reports, the quality and accuracy of recorded data and variability in participant adherence rates to the treatment can cause significant outcome bias. PURPOSE To assess the quality and accuracy of participant documentation of daily self-monitoring of leg skin temperature, adherence to a graduated cooling treatment protocol to prevent venous leg ulcers, and the potential for bias in treatment effect in a randomized controlled trial that included a population with chronic venous disease. METHODS Individuals were randomized to a leg cooling intervention or placebo treatment group to daily self-monitor and record lower leg skin temperature over a 9-month period on monthly paper study logs. Returned study logs for the first 100 completed participants (n=54 cooling intervention, n=46 control) were reviewed for quality and accuracy. Adherence was determined from evaluating the accuracy of participant documentation. To examine potential outcome bias in treatment effect, mean between group and within group comparisons of the before and after treatment differences were conducted using an intention-to-treat (ITT) versus a modified intention-to-treat (mITT) analysis approach with an 85% accuracy cut-off rate. Data were collected in 2011-2014. RESULTS Of the expected 900 study logs, 91.8% (826/900) were returned and 8.2% (74/900) were not. Non-mutually exclusive main error types in returned documentation included: 59.2% (489/826) white-outs, cross-off and/or overwrites, 34.9% (288/826) entries omitted, 29.4% (243/826) no performance of daily self-monitoring, 28.7% (237/826) no performance of the treatment intervention per the prescribed protocol regime, 26.8% (221/826) extraneous data, 8.6% (71/826) suspected fabrication, and 7.6% (63/826) questionable validity. Under ITT analysis, 38.4% (346/900) of all returned logs were <85% accurate, 25.0% (225/900) were 85%-99% accurate, and 36.6% (329/900) were 100% accurate. Mean overall participant adherence rates were: 22.0% at <85% accuracy, 53.0% at 85%-99% accuracy, and 25.0% at 100% accuracy. Under the mITT analysis, 54.0% (483/900) of returned logs were deemed adherent with ≥85% accuracy. CONCLUSION This study found good rates of adherence. Under ITT analysis, 78.0% of participants were deemed adherent to the study protocol with ≥85% accuracy in documenting daily self-monitoring of skin temperatures in response to a topically applied experimental cooling cuff intervention for the prevention of venous leg ulcers.