TABLE 2.

Subgroup analysis for included studies

Subgroups	No. of studies	ES	LCI	UCI	I2	P‐value	Subgroup difference
Method of measurement
ELISA	7	−1.159	−1.977	−0.341	95.70%	0.005	0.055
Luminex	2	−0.105	−0.383	0.174	11.46%	0.461
Others	3	−0.303	−0.792	0.186	66.15%	0.224
Country of study
China	4	−0.718	−2.218	0.692	97.45%	<0.001	0.089
Italy	2	0.073	−0.154	0.299	0%	0.997
USA	2	−0.369	−0.782	0.044	48.91%	0.162
Others	4	0.361	−0.13	0.852	65.14%	0.035
Sex ratio
<50%	2	−0.548	−0.965	−0.13	0.00%	0.01	0.555
>50%	9	−0.804	−1.398	−0.21	95.08%	0.008
Disease duration
≤7 years	4	−0.941	−1.807	−0.074	91.54%	0.033	0.028
>7 years	3	0.005	−0.426	0.436	68.12%	0.982