VARIABILITY AND RELIABILITY OF AIR PLETHYSMOGRAPHIC MEASUREMENTS FOR THE EVALUATION OF CHRONIC VENOUS DISEASE

Purpose: Air plethysmography (APG) has the potential to help evaluate different treatments for the prevention of recurrence of venous ulcers ; however, there are little reported data on the variation and reliabi lity of the different parameters. This study aimed to assess the varia tion in different APG parameters in patients with chronic venous disea se and to evaluate the reliability of APG in test-retest situations. M ethod: Seventeen patients (18 limbs) with chronic venous disease were recruited into this study. Subjects were asked to undergo tests on two occasions, 1 to 6 weeks apart. Three tests were performed at each vis it, and three patients had 10 tests performed at one visit. The coeffi cients of variation were calculated for repeated measurements and test -retest reliability, and the differences between the means of three te sts and the 10 tests were also analyzed. Results: The coefficients of variation for the repeated measurements ranged from 7.5% to 27% for th e majority of parameters of APG. The differences between the means of three tests and the means of 10 tests were less than 10% in this study . The coefficients of variation of method error were approximately 10% in test-retest measures. Conclusions: This study has shown that evalu ations of calf pump function and venous reflux using APG display varia tions in repeated measurements and in the test-retest measures. The va riations found within patients and on retesting patients on different days suggest that APG is very unlikely to be able to detect small chan ges in the parameters of venous reflux and calf pump function. It is e ssential to understand the inherent variation of APG measurements when they are used to assess treatments that are designed to improve venou s function.