Some tests, although not specific, can be helpful in supporting or excluding the possibility of certain systemic rheumatic diseases, as for the following: Antinuclear antibodies (ANA) and anti-double-stranded DNA antibodies in systemic lupus erythematosus (SLE) Rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibodies in rheumatoid arthritis (RA) HLA-B27 in spondyloarthropathy (eg, with symptoms of inflammatory back pain and normal x-rays, or with unexplained uveitis and a peripheral arthritis) Tests such as white blood cell count, erythrocyte sedimentation rate (ESR), and C-reactive protein may help determine the likelihood that arthritis is inflammatory due to infectious or other systemic disorders, but these tests are not highly specific or sensitive.