NOS2 and systemic lupus erythematosus: The meta-analysis showed that SLE patients had higher expression of iNOS at mRNA level than control subjects (SMD = 2.671, 95%CI = 0.446–4.897, z = 2.35, p = 0.019), and a similar trend was noted at the protein level (SMD = 3.602, 95%CI = 1.144–6.059, z = 2.87, p = 0.004) and positive rate of iNOS (OR = 9.515, 95%CI = 1.915–47.281, z = 2.76, p = 0.006) were significantly higher in SLE group compared with control group.