Table 3. Odds ratios for LSIL and HSIL risk according to quartile of the serum folate in the control group.

Serum folate	LSIL				HSIL
	N	Crude OR (95% CI)	Adjusted OR (95% CI)a	P-trendb	N	Crude OR (95% CI)	Adjusted OR (95% CI)a	P-trendb
>22.04	39	Reference	Reference	0.00	10	Reference	Reference	0.00
18.20–22.04	40	1.02 (0.63–1.64)	1.01 (0.62–1.64)		21	2.08 (0.96–4.52)	1.82 (0.83–4.02)
14.13–18.20	75	1.91 (1.25–2.94)	1.85 (1.20–2.86)		33	3.29 (1.58–8.83)	3.28 (1.55–6.92)
⩽14.13	93	2.36 (1.56–3.59)	2.30 (1.51–3.52)		61	6.05 (3.02–12.10)	5.28 (2.60–10.73)

Abbreviations: LSIL, low-grade squamous intraepithelial lesions; HSIL, high-grade squamous intraepithelial lesions; OR, odds ratio; CI, confidence interval.

^aAdjusted for age, education level, annual income, spouse smoking, age at menarche, menopause, age at first intercourse, gravidity, intrauterine device and hrHPV infection.

^bObtained from trend χ² test.