. Author manuscript; available in PMC: 2016 Aug 13.

Published in final edited form as: Birth Defects Res A Clin Mol Teratol. 2016 May 11;106(8):685–695. doi: 10.1002/bdra.23517

TABLE 3.

Folate Receptor (FR) Autoantibodies Immunoglobulin G (IgG) and Immunoglobulin M (IgM) Levels in Maternal Plasma of Neural Tube Defects (NTDs) and Controls, Stratified by Gestational Age, Shanxi Province, China 2011–2013 (N = 317^a)

Autoantibody	Gestational age (weeks)
	≤20				>20
	n	Geometric mean ± SD	Median (IQR)	P-Value^b	n	Geometric mean ± SD	Median (IQR)	P-Value^b
Plasma IgG^c
Total NTDs	17	1.73 ± 0.49	1.89 (0.9–2.63)	0.83	86	1.70 ± 0.23	1.75 (0.76–4.16)	<0.001
Controls	6	1.35 ± 2.13	2.80 (0.58–3.12)		208	0.70 ± 0.05	0.71 (0.34–1.52)
Plasma IgM^c
Total NTDs	17	4.18 ± 0.71	4.11 (2.48–6.17)	0.008	86	3.27 ± 0.32	4.11 (2.06–6.17)	<0.001
Controls	6	1.81 ± 0.99	1.99 (1.29–3.48)		208	2.01 ± 0.11	1.93 (1.24–3.36)

Maternal blood samples were collected from 327 participants; 10 participants were excluded due to missing information on gestational age.

P-value was calculated using Wilcoxon sum-rank test.

Commercialized pooled IgG and IgM from human serum were used to plot the standard curve for detecting FR autoantibody IgG and IgM, respectively. The FR autoantibody IgG and IgM levels in the pooled IgG and IgM were defined as 1.

SD, standard deviation; IQR, interquartile range.