Test-retest Reliability and Minimal Detectable Change in Exercise Oximetry in Claudicants

BACKGROUND

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 were collected from patients that performed 2 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 SEM and intra-class correlation coefficients. MDC was calculated using the formula MDC = SEM x 1.96 x √ 2.

RESULTS

Twenty eight LEAD patients (61 ± 9 years old) were included. Intra-class correlation coefficients 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] mm Hg and 9 [8, 11] mm Hg, respectively. The SEM for all (proximal and distal) DROP values was 8 [7, 10] mm Hg and the MDC of DROP was 23 mm Hg.

CONCLUSIONS

Exercise-TcPO2 with measurement of DROP values has a moderate test-retest reliability in LEAD patients with a maximal walking distance ≤ 300m. For an individual, an improvement or deterioration in DROP of ≥ 23 mm Hg 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.

Performance of finger systolic blood pressure measurement to detect digital occlusive arterial disease in systemic sclerosis

OBJECTIVE

Digital ulcers (DUs) related to digital occlusive arterial disease (DOAD) are frequent in patients with systemic sclerosis (SSc). Finger systolic blood pressure (FSBP) and digital-brachial pressure index (DBI) using laser Doppler flowmetry constitute a non-invasive means of detecting DOAD in SSc, although thresholds have yet to be established for defining DOAD. The purpose of this study was to ascertain FSBP and DBI thresholds to detect DOAD in SSc patients. The intra/interday reproducibility of curve reading by 4 vascular physicians in relation to finger pressure measurement was also investigated.

METHODS

SSc patients were followed in this single-center study (Rennes University Hospital, France) between November 2017 and October 2019.Theses patients underwent tests before and after heating at two visits spaced 10 days apart. DOAD was diagnosed on the basis of post-warming skin blood flow of ≤ 206 arbitrary units measured by LDF, contingent on previous results validated by arteriography as a gold standard. An interday kappa coefficient with a 95% confidence interval was used to assess reproducibility.

RESULTS

16 (10 females; mean age: 63 ± 9 years) SSc patients were included. Mean time interval between visits was 9 ± 5 days. The best FSBP threshold for DOAD diagnosis was 76 mmHg and DBI was 0.74 after warming. FSBP and DBI sensitivity/specificity were 59.1%[49.6%; 68.5%]/92.5% [85.3%; 99.6%] and 73.3%[64.9%; 81.8%]/83.0% [72.9%; 93.1%] respectively. Intra/interday reproducibility ranged from fair to good.

CONCLUSION

The conclusions drawn from this study suggest that FSBP ≤ 76 mmHg and DBI ≤ 0.74 thresholds are potentially reliable indicators of DOAD and demonstrate fair to good intra and interday reproducibility.