Table 3 Multiple linear regression models for neuroendocrine markers and plasma TGF-β in CFS patients with high fatigue score (≥ 20), CFS patients with low fatigue score (< 20), and healthy controls

Model 1

 Dependent variable

  Plasma TGF-β1^a

B (CI)

p value

R²

B (CI)

p value

R²

B (CI)

p value

R²

 Independent variables

  Plasma cortisol

1.9 × 10⁻³ (0.18 to 3.5 × 10⁻³)

0.031

0.17

0.26 × 10⁻³ (− 1.6 to 2.1 x 10⁻³)

0.780

0.12

− 0.19 × 10⁻³ (− 1.9 to 1.5 × 10⁻³)

0.825

0.07

  Urine norepinephrine/creatinine ratio^a

0.99 (0.20 to 1.8)

0.015

0.60 (0.01 to 1.2)

0.048

0.62 (− 0.06 to 1.3)

0.071

  Urine epinephrine/creatinine ratio^a

− 0.65 (− 0.65 to − 0.06)

0.031

− 0.39 (− 0.77 to − 0.02)

0.042

0.004 (− 0.47 to 0.48)

0.987

Model 2

 Dependent variable

  Plasma TGF-β2

B (CI)

p value

R²

B (CI)

p value

R²

B (CI)

p value

R²

 Independent variables

  Plasma cortisol

0.64 (0.22 to 1.1)

0.003

0.22

0.07 (− 0.49 to 0.62)

0.814

0.12

− 0.01 (− 0.49 to 0.46)

0.950

0.05

  Urine norepinephrine/creatinine ratio^a

248 (50 to 447)

0.015

133 (− 44 to 311)

0.136

160 (− 28 to 349)

0.094

  Urine epinephrine/creatinine ratio^a

− 161 (− 308 to − 14)

0.032

− 132 (− 246 to − 18)

0.024

− 16 (− 148 to 115)

0.806

Model 3

 Dependent variable

  Plasma TGF-β3^a

B (CI)

p value

R²

B (CI)

p value

R²

B (CI)

p value

R²

 Independent variables

  Plasma cortisol

2.0 × 10⁻³ (0.60 to 3.4 × 10⁻³)

0.006

0.20

0.17 × 10⁻³ (− 1.6 to 1.9 × 10⁻³)

0.851

0.11

− 0.4 × 10⁻³ (− 1.8 to 0.99 × 10⁻³)

0.565

0.07

  Urine norepinephrine/creatinine ratio^a

0.78 (0.12 to 1.4)

0.022

0.40 (− 0.17 to 1.0)

0.164

0.50 (− 0.06 to 1.1)

0.076

  Urine epinephrine/creatinine ratio^a

− 0.52 (− 1.0 to − 0.03)

0.038

− 0.41 (− 0.77 to − 0.05)

0.027

− 0.01 (− 0.40 to 0.38)

0.964