Perometer

The results showed that the perometer is not as accurate as the water displacement method and perometer tend to overestimate the lower limb volume as compared to the volumeter. This is in contrast with the studies by Man et al. (2004) and Tierney et al. (1996) where the perometer was found to be as accurate as water displacement. This may be partly explained by the self-protective mechanism of the participants, as they seemed slightly sensitive to the “invasiveness” of the perometer frame, when the frame moves all the way up to the groin area. The participants may have tried to reduce the possible contact of the frame with their sensitive area through increased hip abduction, or slight tiptoes, resulting in more limb volume captured.

The lack of agreement is demonstrated by the large variation of the ±1.96 SD (1224ml) from the Bland-Altman difference plot and the t value. As the mean difference in limb volume between the two methods is clinically unacceptable (832ml) with a wide 95% confidence interval (659-1000), any limb volume change observed clinically may simply be due to errors in measurement if used interchangeably. Therefore, it is not recommended for the perometer and volumeter to be used interchangeably for measuring lower limb volume. This finding coincides with the study by Man et al. (2004) where the authors also found that both methods are not interchangeable.
The Bland-Altman plot finding from the study raises the issue of test-retest reliability for the limb volume measurement methods.
This study showed that excellent test-retest reliability of the perometer method (ICC(3,1) = 0.994). This shows that the perometer is a reliable tool which can produce stable and consistent measurements, thus any limb volume change observed clinically may be due to treatment effect or disease progression. This coincides with the consensus from other literatures that the perometer has high
reproducibility.