The agreement and test retest reliability of the perometer when compared to a water displacement method for measuring lower limb volume in healthy individuals.
(2017) The agreement and test retest reliability of the perometer when compared to a water displacement method for measuring lower limb volume in healthy individuals., no. 37.
Question: Does the vertically oriented perometer demonstrate high test-retest reliability and agreement as a measure for lower limb volume when compared to the reference standard water displacement? Design: Between-methods agreement and test-retest reliability study. Participants: Fifteen healthy University students were recruited using convenience sampling with no participant dropouts. Intervention: All participants' dominant lower limb volume was measured using the vertically oriented perometer and the water displacement method. Outcome measures: The ICC (3,1) model and SEM were used to establish the test-retest reliability for both methods. A one-sample t-test was used along with the Bland-Altman difference plot to determine bias between the two methods and its 95% confidence interval. Results: Test-retest reliability of the water displacement method was ICC(3,1)=0.986 with measurement error=204ml. The test-retest reliability of the perometer method was ICC(3,1)=0.994 with measurement error=146ml. There was a lack of agreement between the perometer and water displacement method. The one-sample t-test was statistically different with t(14)=10.315, p≤0.001, 95% CI (659-1005). The Bland-Altman difference plot showed that the perometer method overestimated limb volume by 832ml compared to the water displacement method. A 95% confidence interval with limits of agreement 219ml to 1444ml was observed. Conclusion: There was excellent test-retest reliability and low SEM for both methods, however a lack of agreement between the two methods was observed. Therefore the perometer and water displacement methods are not interchangeable. It is recommended that future validity and reliability studies for the perometer are conducted on clinical populations with larger sample sizes.