Table 1. Estimates of cardiorespiratory fitness and HF biomarkers and comparison with literature threshold references.

Test	Mean response	R2 adjusted	RMSE	CV	Threshold References
OUES 10 predictors (n = 47)	1.68 (1.53–1.83)	0.857 (0.742–0.896)	0.195 (0.186–0.235)	0.12	1.47 Davies et al[17]
Exercise duration 11 predictors (n = 49)	6.99 minutes (6.24–7.74)	0.864 (0.780–0.892)	0.973 (0.933–1.117)	0.14	7.50 minutes Florea et al[18]
Peak VO2 15 predictors (n = 48)	13.81 mL·kg-1·min-1 (12.94–14.71)	0.864 (0.775–0.886)	1.145 (1.120–1.353)	0.08	14.00 mL·kg-1·min-1 Arena et al[19]
VE/VCO2 Slope 13 predictors (n = 45)	33.83 (32.08–35.61)	0.863 (0.756–0.896)	2.270 (2.183–2.705)	0.07	32.90 Shen et al[20]
NT-proBNP 12 predictors (n = 46)	1550 pg/mL (1244–1958)	0.870 (0.710–0.906)	442 (430–502)	0.29	≥900 pg/mL (50–75 years), ≥1800 pg/mL pg/mL (>75 years) Shah et al[21]
Galectin-3 12 predictors (n = 46)	19.90 ng/mL (18.00–22.11)	0.868 (0.766–0.903)	2.576 (2.365–3.178)	0.13	19.00 ng/mL Carrasco-Sanchez et al[22]
CRP 15 predictors (n = 45)	6.45 mg/L (5.11–8.21)	0.857 (0.725–0.890)	2.006 (1.936–2.323)	0.31	6.91 mg/L Mommersteeg et al

The mean response are values of the CPET and HFBio calculated from the regression parameters and a given value of the predictors that best fit the model. RMSE is presented as an absolute measure of fit in the same unit as the mean response. CV was calculated using the rate of RMSE by the mean response. Threshold references for test prediction of CHF outcome is presented as a measure of comparison of the mean response with peer reviewed publications. Bootstrap 95% CI are presented as a measure of validation, and are generally larger than 95% CI calculated from the actual data. Peak VO₂ = peak oxygen consumption; OUES = oxygen uptake efficiency slope; VE/VCO₂ = minute ventilation-carbon dioxide production; NT-proBNP = N-terminal pro-B-type natriuretic peptide; CRP = C-reactive protein; L/min = liters per minute; RMSE = root mean square error; CV = coefficient of variation.