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ASSOCIATION OF 2-MINUTE STEP TEST PERFORMANCE WITH CARDIORESPIRATORY FITNESS IN OLDER ADULTS WITH HIV

Abstract

BACKGROUND: Cardiorespiratory fitness (CRF) is an independent predictor of mortality yet requires specialized equipment to measure peak oxygen utilization (VO2peak). Identifying alternative tests, which can be conducted in a clinical setting, is a priority for patient populations with substantial impairment in CRF, such as people with HIV (PWH). Our objective was to determine if the two-minute step test (2-MST), conducted by video teleconferencing, predicted VO2peak in PWH. METHODS: Participants were PWH ≥ 50 years of age who were clinically stable and eligible for a telehealth exercise training intervention. Baseline cardiorespiratory exercise test (CPET) was performed on a treadmill using the modified Bruce protocol to measure VO2peak and maximum heart rate (HRmax). Baseline functional performance was measured using video conferencing technology between different VA medical centers and included 2-MST, 10 time sit-to-stand test, arm curl, and 8-foot up and go. The step count on 2-MST was classified as low or high based on the median value (80 steps). Percent of age predicted HRmax (APMHR) was calculated using formula 208 - (0.7 x age). Two-tailed tests of associations were used with values expressed as mean (standard deviation). RESULTS: The 72 participants were 62.8 (6.7) years old, 88% Black, and 95% men. CPET showed VO2peak = 23.4 (5.5) mL/kg/min, treadmill duration =13.6 (3.4) minutes, %APMHR=95(8)%, and RER= 1.12 (0.11). Based on Pearson’s correlation, the number of steps in 2-MST was associated with VO2peak (r=0.44, p<0.001) and time on treadmill (r=0.48, p<0.001). 2-MST also correlated with other functional performance measures (p-values <0.01) and age (r= -0.43, p<0.001). There was a significant difference in VO2peak between participants with 2-MST classified as low (n=36) versus high (n=37) (mean (SD) ml/min/kg: 21.6 (5.3) vs. 25.0 (5.1), p<0.01). Age adjusted linear regression showed 2-MST predicted VO2peak (beta (95%CI)= 0.065 (0.008,0.123), p=0.027). CONCLUSIONS: Our findings demonstrated that performance in the 2-MST conducted by video conferencing is significantly associated with CRF, independent of age in PWH. The difference in VO2peak between low and high number of steps is approximately 1 MET, suggesting a clinically meaningful difference. In telehealth or space-limited settings, the 2-MST should be considered as an estimate of CRF in older patient populations with reduced fitness. Grant or funding information: VA Office of Research and Development (ORD), Rehabilitation Research and Development, I01 RX002790 (Oursler/Ryan/Marconi)

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