1st order laboratory parameters – obligatory laboratory tests.
- Small blood count
- Differential blood count
- Inflammatory parameters – CRP (C-reactive protein) [↑ ; about 50% of cases] or ESR (erythrocyte sedimentation rate) [↑; normal ESR: about 20-30% of cases].
- Detection of the HLA-B27 allele in the HLA-B gene [positive in 90-95% of cases].
- Rheumatoid factor [negative]
- Antinuclear antibodies (ANA) [negative].
During the course of the disease, the following parameters may be altered:
- Alkaline phosphatase
- Serum IgA
