Laboratory examination include erythrocyte sedimentation rate (ESR), blood cell counts, white cell differentiation, CRP, ASAT, ALAT, GGT, creatinine, uric acid, LDH, Ca, AP, phosphate, urine status and serologic tests for Rheumatoid Factors (RF), cyclic -citrullinated peptides (CCP) -antibodies, ANA, HLA-B27, IgG, IgA, IgM as well as infectious diseases, Hepatitis B surface-antibody titer, Measles- antibody titer, Varicella-Zoster-virus- antibody titer if vaccination status is uncertain. Here, BTG3 is linked to infectious disease.