Table 2.

Calprotectin in Rheumatic Diseases. This table summarizes the main findings of calprotectin levels and rheumatic diseases other than RA.

Disease	Calprotectin source	Main finding
Reactive arthritis	Plasma and synovial fluid.	• CLP correlated with CRP and disease activity (79). • CLP was the first biomarker to return to baseline levels after disease improvement (79).
Ankylosing spondylitis	Serum	• CLP correlated with PGA, pain VAS, BASDAI, BASFI, and ASDAS (80, 81). • CLP is an independent marker for radiographic progression (82).
Psoriatic arthritis	Serum	• CLP levels are significantly higher in active PsA patients than in healthy controls (83). • Higher CLP levels were found in the polyarticular group than in patients with mono/oligoarticular disease (84). • CLP levels are sensitive to change, and its levels decrease after TNFi and IL17i treatment (83).
Systemic juvenile idiopathic arthritis	Serum	• CLP levels are sensitive to change (85). • CLP more accurately predicts disease relapse (86).
Adult onset Still disease	Serum	• CLP levels are significantly higher than RA, SLE patients or controls (87, 88).
Gout	Serum, synovial biopsy and tophi	• CLP levels were elevated in the synovium, tophi, and serum of patients with gout (89). • CLP levels correlated with disease activity (89).
Systemic lupus erythematosus	Urine	• CLP levels in SLE-LN patients (90). • CLP levels correlated with disease activity (91).
Primary Sjogren syndrome	Serum, saliva and salivary gland biopsy.	• Increased levels in pSS patients (92, 93).
Systemic sclerosis	Serum, broncho-alveolar lavage fluid, skin biopsy	• Increased levels in SSc patients (94, 95). • Increased levels in diffuse cutaneous SSc patients (96).
Behcet’s disease	Serum	• CLP levels are significantly higher than healthy controls (97). • CLP correlated with CRP and disease activity (97)
Idiopathic inflammatory myopathies	Serum and muscle biopsy	• Increased levels in IIM patients (98). • CLP promotes myoblast activation (99).

CLP, calprotectin; PGA, patient global assessment; pain VAS, pain visual analogue scale; BASDAI, Bath AS disease activity index; BASFI, the Bath AS functional index; ASDAS, Ankylosing Spondylitis Disease Activity Score; TNFi, TNFn inhibitors; IL17i; interleukin 17 inhibitor; SLE-LN, SLE-lupus nephritis.