Inter-observer and Intra-observer Variability in Volume Measurements of the Lower Extremity Using Perometer

The swelling of the extremities seen in lymphedema can be measured with many different volumetric devices; however, many methods lack important characteristics including reproducibility and independence from the subjectivity and skill of the operator. The aim of this study was to validate the use of the Perometer^® as a possible standard for volumetric measurement methods based on the inter-observer and intra-observer variability when using a standard method of Perometry^®. Volumetric measurements were performed on 10 healthy test subjects by 5 individuals (the observers) who had been instructed in the measurement techniques to be used. The inter-observer variability was assessed by having the five observers measure all the test subjects both in the morning and in the early afternoon. The intra-observer variability was examined by having each observer measure all the 10 test subjects 4 times in a row in the aforementioned time frames. A data set was created using the measurements, allowing for the assessment of other parameters including variation of volume between the right and left leg and daily variation in swelling. Statistical measurements were performed using the Statistical Package for the Social Sciences (SPSS), from which it was determined that there was no statistically significant inter-observer (p-value 0.997) and intra-observer variation (p-value 0.995) based on a significance level of >5%. Furthermore, it was observed that a statistically significant difference in volume occurred in the leg volume during the day. It was concluded that the use of the Perometer provides consistent measurements of volume independent of the observer and therefore appears to provide a candidate standard for volumetric measurements.