Table 5. Pooled results for the association between P16^INK4a promoter hypermethylation and CC risk.

Comparisons	Studies (N)	Sample size (CC/controls)	Heterogeneity		Model a	Effect size
			I2(%)	PQ-test		OR (95% CI)	P
Total	18	950/732	58	0.001	R	12.17 (5.86-25.27)	< 0.001
Ethnicity
Asian	10	631/385	19	0.272	F	18.94 (9.75-36.81)	< 0.001
Caucasian	5	270/200	60	0.039	R	6.83 (1.98-23.55)	0.002
Other ethnicities	3	135/179	88	< 0.001	R	9.87 (4.45-21.90)	< 0.001
Source of controls
Healthy	9	322/267	44	0.073	R	13.67 (5.64-33.10)	< 0.001
Non-healthy	9	628/465	69	0.001	R	11.32 (3.28-39.05)	< 0.001
Quality of studies
High (≥ 12)	11	583/491	0	0.495	F	18.81 (10.84-32.63)	< 0.001
Low (< 12)	7	427/311	77	< 0.001	R	8.83 (1.85-42.11)	0.006

^aWhen significant heterogeneity was found (I²≥ 50% or P_Q-test ≤ 0.1), the random-effects model (DerSimonian-Laird method) was used to pool the results; otherwise, the fixed-effects model (Mantel-Haenszel method) was applied.

^bNon-healthy controls included autologous controls (normal tissues adjacent to HSIL specimens), controls with benign gynecological diseases and mixed controls.

Abbreviations: N, number; CC, cervical cancer; R, random-effects model; F, fixed-effects model.