TABLE 4.

Linear regression models for cytotoxicity capacity of NK cells (dependent variable)¹

	Independent variables	Unstandardized Coefficients		Partial R2	P
		β	SE
Univariate Models
1	Intervention with 5 mg FA/d	−0.399	0.141	–	0.006
2	Serum total folate2	−0.006	0.002	–	0.001
3	Serum Folate3	−0.007	0.002	–	0.002
4	Serum UMFA	−0.005	0.002	–	0.040
5	Serum 5-methyl-THF	−0.012	0.004	–	0.001
6	Serum THF	−0.544	0.208	–	0.011
7	Serum Mefox	−0.032	0.115	–	0.782
8	Serum vitamin B-12	−0.001	0.001	–	0.583
9	Plasma total homocysteine	0.093	0.053	–	0.082
10	LDH	−0.001	0.002	–	0.572
11	hs-CRP	−0.376	0.310	–	0.230
12	Serum IL-6	0.677	0.174	–	<0.001
13	Serum IL-8	0.026	0.048	–	0.592
14	Serum IL-10	0.095	0.049	–	0.057
15	Serum IFN-γ	0.060	0.021	–	0.006
16	Serum TNF-α	−0.154	0.052	–	0.004
17	DHFR del19bp	0.102	0.176	–	0.565
18	Expression of mRNA of DHFR	−2.738	6.245	–	0.662
19	Expression of mRNA of IFNG	−13.728	14.796	–	0.356
20	Expression of mRNA IL8	0.008	0.043	–	0.847
21	Expression of mRNA of TNFA	−0.234	0.372	–	0.530
22	BMI	0.051	0.039	–	0.194
Multivariate models
23	Serum 5-methyl-THF	−0.011	0.003	0.092	0.001
	Serum IL-6	0.759	0.224	0.083	0.001
	Serum IFN-γ	0.053	0.025	0.032	0.039
	Serum TNF-α	−0.198	0.046	0.137	<0.001

¹The dependent variable was the log of cytotoxic capacity of NK cells. DHFR, dihydrofolate reductase; FA, folic acid; hs-CRP, highsensitivity C-reactive protein; IFNG, interferon-γ; LDH, lactate dehydrogenase; MeFox, oxidation product of 5-methyl-THF; THF, tetrahydrofolate; TNFA, tumor necrosis factor-α; UMFA, unmetabolized folic acid.

²Derived by using HPLC–tandem MS.

³Derived by using a microbiological assay.

⁴Multivariate linear regression (model 23): The independent variables included were those with P < 0.05 in univariate model. The variables that showed strong correlations with 5-methyl-THF were excluded from the model (intervention, serum folate, and serum total folate).

Critical value of Bonferroni correction: P = 0.0125.