1st order laboratory parameters – obligatory laboratory tests.
- Small blood count
- CRP (C-reactive protein) [+ /-] or ESR (erythrocyte sedimentation rate) [+ /-].
- HLA-B27 (positive in 50-70% of cases) – indication of spondyloarthritides (inflammatory rheumatic disease predominantly affecting the spine).
- Anti-citrulline antibodies – antibodies against cyclic citrullinated peptides (ACPA, CCP-Ak, anti-CCP) [up to 8% positive].
- Rheumatoid factor (RF) [positive: 5-10%]
- Biopsy (tissue sample) for histological examination.
