Table 3. Folate, vitamin B₁₂ and homocysteine concentrations in cases and controls.

	Serum folate (nmol l−1)	Serum vitamin B12 (pmol l−1)	Plasma total homocysteine (µmol l−1)	Red cell folate (nmol l−1)
Comparison of metabolite concentrations between cases and controlsa
Non-users of vitamins
Cases (n=110)c	12.89±5.92	281.18±84.18	13.25±5.86	649.14±203.61
Controls (n=123)c	14.73±6.00	300.23±91.76	12.77±7.59	714.48±223.36
P value (adjusted for age, smoking, abstinence time)	0.0063	0.44	0.077	0.044
P value (adjusted for age, smoking, abstinence time, education)	0.022	0.80	0.10	0.16
Users of vitamins with folic acid
Cases (n=32)c	26.81±18.59	355.96±124.35	10.57±2.77	984.32±333.63
Controls (n=34)c	25.46±14.94	346.44±104.98	10.29±1.90	1022.15±315.90
P value (adjusted for age, smoking, abstinence time)	0.84	0.48	0.73	0.55
P value (adjusted for age, smoking, abstinence time, education)	0.51	0.46	0.83	0.47
Risk of infertility (case–control analysis) associated with metabolite concentration, among non-users of vitaminsb
OR (95% CI): adjusted for age, smoking, abstinence time	0.36 (0.16, 0.78)	0.66 (0.23, 1.85)	3.18 (0.81, 12.47)	0.28 (0.08, 1.02)
P value	0.0094	0.43	0.097	0.054
OR (95% CI): adjusted for age, smoking, abstinence time, education	0.40 (0.18, 0.90)	0.87 (0.29, 2.64)	3.01 (0.78, 11.62)	0.32 (0.08, 1.30)
P value	0.027	0.81	0.11	0.11

^aComparison using linear regression models; model covariates are listed as adjustment factors.

^bLogistic regression used to generate odds ratios (OR) and 95% confidence intervals (CI); each metabolite was examined in a separate model; model covariates are listed as adjustment factors.

^cValues are presented as mean ± s.d..