OA01.03. Sample size and regions of principally achievable significance in cost effectiveness studies: an example of complementary medicine

Abstract

Purpose: Health economic studies gain more and more importance in both conventional and complementary medicine. In most cases such studies are conducted as a combination of a RCT and a health economic evaluation (" Piggy-Back-Studies "). Therefore study planning parameters like sample size still are calculated on the basis of the outcome of the clinical parameters. This might lead to situations of underpowering. Methods: Based on the sample size estimates given in Glick (2011), we aimed at finding health economic studies of CAM providing mean and standard deviation data on cost and outcome differences. Based on this data and on assumptions on willingness to pay and cost-outcome correlation, we constructed a model of principally achievable significance. Results: Based on an existing review on health economic studies in CAM, 8 of 143 studies mentioned sample size calculation parameters. However, only one study (Lin et al. 2008) provided enough data for modelling. We found a significant discrepancy between the sample size of n=46 based on conventional sample size calculation and the hypothetically needed patients of more than 350 based on our modelling approach. Conclusion: Planning health economic studies should be done with great caution not to end in a situation of small power. Our approach might retrospectively give estimates of regions of significance and thus might help to interpret health economic studies not only in the field of CAM. O4 OA01.04. The effectiveness and cost effectiveness of acupressure for chemotherapy-related nausea Purpose: To assess the clinical effectiveness and cost effectiveness of self-acupressure using wristbands in addition to standard care in the management of chemotherapy-induced nausea. Methods: Randomised three-group sham-controlled trial. Patients with heterogeneous cancer diagnoses receiving low, moderate and highly emetogenic chemotherapy randomised to receive, in addition to standardised antiemetics, either acupressure wristbands, sham acupressure wristbands or antiemetics alone. Patients were instructed to wear the wristbands for 7 days during each cycle of chemotherapy. Patients participated for 4 cycles of chemotherapy. An economic evaluation was carried out based on drug and health service utilisation. A nested qualitative interview study was also incorporated to shed more light into quantitative findings. Results: 500 patients randomised in the three study groups. Primary outcome analysis (nausea in cycle (1) revealed no statistically significant differences between the three groups. When the two wristband groups were examined together against antiemetics only, statistical level almost reached significance (p=0.07). No significant differences were detected in relation to vomiting outcomes, anxiety, and quality of life measures. The cost-effectiveness evaluation revealed that both real and sham wristbands were associated with reduced costs compared to the antiemetics group only (p<0.001). The qualitative data suggested that patients perceived the wristbands (both real and sham) as effective and helpful to manage their nausea experience. Minor and transient side effects from the use of the wristbands were observed. Conclusion: No clear recommendations can be made about the use of acupressure wristbands in the management of chemotherapy-related nausea, as results did not reach statistical significance. However, the use of wristbands was associated with significant health care cost-savings, they were safe and perceived to be effective by patients. Before rejecting this intervention, we need to consider the therapeutic effects of placebos in situations such as the management of nausea with a low-cost and safe intervention that may enhance the effect of antiemetic drugs.