Background The Alfred Step Test Exercise Protocol (A‐STEP) and feasibility study were previously published. The aim here was to determine the validity of the A‐STEP compared to cycle ergometry (CPET) in adults with CF. Methods The A‐STEP and CPET were carried out in random order 2 weeks apart. A wearable, portable metabolic system was used to measure breath‐by‐breath and minute‐by‐minute sampling of O 2 , CO 2 , heart rate, and VO 2 . The main outcome measures were VO 2max and HRmax. Results Seven stable‐state adults (3 male) on CFTR modulator therapy with a mean (SD) and range of age 38.2 (13.4) 26–64 years; height 169.9 (10.9) 149.7–185.3 cm; BMI 22.8 (2.10) 19.5–28 kg/m 2 ; FEV1 79.4 (18.9) 38.0–106.0; and FVC 95.1 (16.7) 63.0–114.0 percent predicted (pp) completed both A‐STEP and CPET. The VO 2Max had high correlation and good agreement between the A‐STEP 31.3 (5.9) and CPET 29.8 (6.2) mL/min/kg, r = 0.88. The HR MAX was strongly correlated with the A‐STEP 174 (17) bpm and 95.7 (7.4) pp versus 168 (15) bpm and 92.4 (5.3) pp with r = 0.92 and 0.86, respectively. The SpO 2Nadir for A‐STEP was 91.0 (4.0) and CPET 92.0 (3.3), r = 0.82. The VO 2 at the anaerobic threshold (VO 2@AT ) occurred significantly earlier for the CPET at 1021 (260) versus A‐STEP 1361 (234) mL/minute, p < 0.05. The VE Max for CPET was 84.1 (18.8) and A‐STEP 73.5 (15.8) L/minute, p < 0.05. The AWESCORE also ensured baseline stability. The number of levels completed during the A‐STEP was 10.7 (12.9) ranging from 9 to 15. Conclusion The A‐STEP may be a portable, valid surrogate to cardiopulmonary exercise testing using cycle ergometry.
Button et al. (Thu,) studied this question.
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