Calprotectin, a sensitive marker of inflammation, is robustly assessed in plasma from patients with early or established rheumatoid arthritis by use of different laboratory methods

Figures & data

Figure 1. Spearman’s correlation at baseline between calprotectin levels examined by use of ELISA or FEIA in the ARCTIC cohort of early RA (A) as well the ULRABIT cohort of established RA (B).

Table 1. Spearman’s rank correlations at baseline between calprotectin (assessed by ELISA or FEIA)/CRP/ESR and clinical as well as ultrasound assessments of disease activity in the cohorts of early or established RA (p < 0.001 for all correlations).

Cohort	US/clinical assessment	Calprotectin ELISA	Calprotectin FEIA	CRP	ESR
Early RA (n = 212)	Sum score Grey scale	0.44	0.40	0.43	0.32
	Sum score power Doppler	0.40	0.38	0.38	0.38
	Swollen joint count	0.29	0.34	0.41	0.27
	Examiner’s global VAS	0.34	0.39	0.48	0.33
Established RA (n = 177)	Sum score Grey scale	0.45	0.54	0.37	0.23
	Sum score power Doppler	0.47	0.56	0.43	0.31
	Swollen joint count	0.32	0.39	0.25	0.27
	Examiner’s global VAS	0.47	0.56	0.45	0.50

RA: rheumatoid arthritis; US: ultrasound; ELISA: Enzyme-Linked Immuno Sorbent Assay; FEIA: Fluoro Enzyme Immuno Assay; CRP: C-reactive protein; ESR: erythrocyte sedimentation rate; VAS: visual analogue scale (0–100).

Data availability statement

The data will be shared if there is a reasonable request for it.