Table 4 Associations between calprotectin, tumour necrosis factor inhibitor trough serum levels and power Doppler ultrasound synovitis

Calprotectin, μg/ml

3.22 (1.95–5.33)

<0.0001

4.63 (2.31–9.26)

<0.0001

TNFi trough serum levels, μg/ml

0.77 (0.65–0.91)

0.002

0.67 (0.52–0.85)

0.001

Age, years

1.03 (0.99–1.06)

0.164

Disease duration, years

1.05 (1.00–1.10)

0.067

1.10 (1.02–1.18)

0.016

ESR, mm/h

1.13 (1.05–1.22)

0.001

Female sex

2.92 (1.18–7.20)

0.020

Combined therapy, yes or no

1.64 (0.72–3.76)

0.245

Disease activity according to DAS28-ESR

0.001

Remission (<2.6)

1

Low disease activity (2.6–3.2)

7.35 (2.23–24.21)

Reduced dose, yes or no

0.63 (0.27–1.44)

0.271

Diagnostic

0.002

 RA

1

 PsA

0.26 (0.11–0.62)

Steroids, yes or no

2.67 (0.83–8.55)

0.099

18.12 (2.73–120.16)

0.003

Monotherapy, yes or no

0.59 (0.26–1.34)

0.206

Constant

0.02 (0.003–0.16)

<0.0001