A test-retest reliability and between-methods agreement study comparing the Infrared Optoelectronic volumetry and Infrared Depth volumetry against the Water Displacement volumetry, for the measurement of lower limb volumes in healthy individuals.
Question: Does infrared optoelectronic volumetry and infrared depth volumetry demonstrate higher test-retest reliability and agreement when compared to the reference standard water displacement volumetry for the measurement of lower limb volumes? Design: Test-retest reliability and between-methods agreement study Participants: 13 healthy university students were recruited using convenience sampling without any participant dropouts Intervention: All participants’ dominant lower limb volume was measured using water displacement volumetry, infrared optoelectronic volumetry and infrared depth volumetry. Outcome measures: The test-retest reliability of each method was computed using ICC(2,1) model and SEm. A Bland and Altman difference plot was used to determine the limits of agreement between infrared optoelectronic volumetry and infrared depth volumetry to water displacement volumetry and its 95% confidence intervals. Results: Test-retest reliability and SEm of water displacement volumetry, infrared optoelectronic volumetry and infrared depth volumetry were ICC(2,1)=0.950 and SEm=367 ml; ICC(2,1)=0.933 and SEm=398 ml; and ICC(2,1)=0.891 and SEm=579 ml respectively. The Bland and Altman difference plot demonstrated that both the infrared optoelectronic volumetry and infrared depth volumetry overestimated limb volume by 1529 ml (95%CI = -211 to -2487 ml) and 1502 ml (95%CI=-466 to -2538 ml) respectively as compared to water displacement volumetry. Conclusion: There were excellent test-retest reliability for water displacement volumetry and infrared optoelectronic volumetry and good test-retest reliability for infrared depth volumetry. However, a lack of agreement between-methods was observed. Therefore, each methods cannot be used interchangeably.