Table 5. Correlation of diffusing capacity with total serum IgG and IgG subclasses in IgG4-RRD group.

Diffusion capacity	P and r values	Total serum IgG	Serum IgG4	Serum IgG3	Serum IgG2	Serum IgG1
DLCO	r value	−0.690*	−0.608	−0.870**	−0.828**	−0.377
	P value	0.043	0.062	0.002	0.006	0.318
DLCO/VA	r value	−0.661*	−0.761*	−0.450	−0.700*	−0.317
	P value	0.038	0.037	0.224	0.036	0.406

Serum IgG, IgG3, and IgG2 levels were significantly negatively correlated with D_LCO. Serum IgG, IgG4, and IgG2 levels were significantly negatively correlated with D_LCO/V_A (* and ** indicate significance at the 0.05 and 0.01 level, respectively, n=9). D_LCO, diffusing capacity of the lung for carbon monoxide; D_LCO/V_A, D_LCO per liter of alveolar volume.