The combination of antinuclear antibodies (ANA) positivity (titer ≥ 1:80) and decreased C3 and C4 levels in pleural effusions demonstrated a sensitivity of 82%, specificity of 89%, and a negative predictive value of 93% for distinguishing lupus pleuritis from non-lupus exudative pleural effusion [24, 25]. This evidence concerns the gene C4A and Pleural effusion.