Figure 1.

Study design: the 2015 Standards for Reporting Diagnostic Accuracy (STARD) flow diagram of the cross-sectional study. ESR – erythrocyte sedimentation rate; CRP – C-reactive protein; CH⁵⁰ – 50% hemolytic complement activity of serum; C – complement component; ANA – anti-nuclear antibody; RF – rheumatoid factor; MCP – metacarpophalangeal; PIP – proximal interphalangeal; MTP – metatarsophalangeal. The 2015 Standards for Reporting Diagnostic Accuracy (STARD) guidelines (http://www.stard-statement.org).