The reliability, validity and sensitivity to change over time of the figure of eight method measuring hand size in patients with breast cancer related lymphoedema

Breast cancer related lymphoedema (BCRL) affects approximately 21% of patients following treatment for breast cancer. The current gold standard method of measuring hand swelling associated with BCRL is to use water displacement (volumeter). However, this is not always possible in the clinical setting. The circumferential tape measurement method is often used clinically but this does not include the area on the dorsum of the hand where the oedema is most commonly situated. The figure of eight method, which involves wrapping a simple measuring tape around the hand in a specific way, may be an alternative method to measure BCRL. The aim of this study was to determine whether the figure of eight tape method was a valid and reliable method of measuring hand size in patients with hand oedema associated with BCRL. This was investigated by comparing the figure of eight tape method of measurement against the “gold standard” method of water displacement. The aim was also to establish whether the figure of eight tape method of measurement was reliable and valid for novice practitioners to ensure that the method could be used by any practitioner assessing a patient with BCRL. It was also investigated whether the figure of eight method of measurement was sensitive enough to detect change in hand size over time. In study 1, 24 patients with hand swelling associated with BCRL participated. Two novice testers performed three “blinded” figure of eight measurements and three volumetric measurements of the affected hand. In terms of inter-tester and intra-tester reliability, the intraclass correlation coefficients were all greater than 0.8 indicating high intra- and inter-tester reliability for the figure of eight method. For validity, a Pearson moment correlation was used to compare the figure of eight and volumetric methods. The results demonstrated a statistically significant correlation of 0.7 for both testers. The results from this study, therefore, found the figure of eight method to be a valid and reliable method of measuring hand swelling in this population, even when measurements were made by novice practitioners. Ten subjects, with hand oedema associated with BCRL, participated in study 2. One tester, who was an experienced lymphoedema practitioner, performed three “blinded” sets of figure of eight measurements, circumferential measurements and volumetric measurements of each hand. These measurements were taken at the start of a course of treatment for lymphoedema management and then again at the end of this treatment course. In terms intra-tester reliability, the intraclass correlation coefficients (3.1) were all greater than 0.9 for each of the measurement methods indicating high intra-tester reliability. For validity, a Pearson moment correlation was used to compare the results from the figure of eight and volumetric methods, and showed a statistically significant and strong correlation of 0.7 between these methods. The Pearson moment correlation between volumeter and circumferential measurement was 0.6 which indicated a good correlation, suggesting this method was also valid. In this study, sensitivity to change in hand size was also considered using the Wilcoxon signed rank confidence interval and, of the three measurement methods, only the figure of eight method indicated a difference in the pre and post treatment measurements. This may suggest this method is sensitive enough to detect change in hand size over time. It was recognized, however, that this study was carried out on a small sample. Further studies are required to investigate the sensitivity to change in hand size of this method on a larger sample. The study also highlighted the natural variability that occurred in the unaffected hand over the course of the treatment time and therefore, future work to establish the extent of this variability would enable the identification of a clinically significant change in hand size with treatment. The studies would support the use of the figure of eight method for monitoring hand oedema in patients presenting with BCRL. The early results, albeit on a small sample, indicate that the figure of eight method may be valid, reliable and responsive to change over time. The figure of eight tape measurement method is suitable for all patients, is inexpensive, quick and does not require specialist training.