Test-retest reliability and minimal detectable change in exercise oximetry in claudicants.

OBJECTIVE: Exercise transcutaneous oxygen pressure measurement (Exercise-TcPO2) can be used to diagnose Lower Extremity Artery Disease (LEAD) and allows the quantification of limb ischemia during exercise on treadmill. Exercise-TcPO2 test-retest reliability in patients with LEAD and severe walking impairment is unknown. The aim of this study was to evaluate the test-retest reliability, standard error of measurement (SEM) and Minimal Detectable Change (MDC) of exercise TcPO2 in patients with claudication.

METHODS: Data was collected from patients that performed two treadmill tests within a 1-month interval. Delta from Rest of Oxygen Pressure (DROP) values were measured at both buttocks (proximal) and both calves (distal). Test-retest reproducibility was assessed by recording transcutaneous oximetry measurements twice and expressed as standard error of measurement (SEM) and intra-class correlation coefficients (ICC). MDC was calculated using the formula MDC = SEM x 1.96 x √ 2.

RESULTS: Twenty-eight LEAD patients (61+/-9 years old) were included. ICCs were 0.66 [0.50, 0.79] and 0.65 [0.49, 0.79] for the proximal and distal levels respectively. The SEM of DROP at the proximal and distal levels were 7 [6, 9] mmHg and 9 [8, 11] mmHg, respectively. The SEM for all (proximal and distal) DROP values was 8 [7, 10] mmHg and the MDC of DROP was 23 mmHg.

CONCLUSION: Exercise-TcPO2 with measurement of DROP values has a moderate test-retest reliability in LEAD patients with MWD≤ 300m. For an individual, an improvement or deterioration in DROP of ≥ 23 mmHg after an intervention would be required to be 95% confident that the change is significant. It should be considered in evaluating the impact of treatment in patients with claudication.