Human papillomavirus infection and gastric cancer risk: A meta-epidemiological review

Table 1 The summary odds ratio with its 95%CI from two systematic reviews

Ref.	Search to	Subgroup	Case-control studies	sOR (95%CI)	I2 (%)
Zeng et al[11], 2016	Jun 2016	All	15	7.39 (3.88-14.1)	56.7
Wang et al[5], 2020	Apr 2020	All	14	1.53 (1.00-2.33)	59.8
		Chinese	5	1.98 (1.04-3.75)	73.7
		Non-Chinese	9	1.17 (0.68-2.02)	33.4
		Tissue	11	2.24 (1.13-4.43)	66.5
		Serum	3	1.04 (0.75-1.44)	0.0
		HPV-16	8	2.42 (1.00-5.83)	67.5
		HPV-18	3	1.08 (0.59-1.99)	0.0

HPV: Human papillomavirus; sOR: Summary odds ratio.

Table 2 Extracted information of the 18 selected case-control studies

Ref.	Year	Nation	Site	Test	Sample	PCa	NCa	PCo	NCo
Sha et al[19]	1998	China	Gastric	PCR	FFPE	27	38	4	61
Dong et al[20]	1999	China	Gastric	PCR	Other	10	27	0	20
Yu et al[21]	1999	China	Gastric	PCR	FFPE	30	102	3	101
Zhou et al[22]	1999	China	Gastric	PCR	FFPE	19	31	0	20
Zhu et al[23]	2000	China	Gastric	PCR	FF	11	31	0	42
Liao et al[24]	2001	China	Gastric	ISH	Other	26	24	2	28
Xu et al[25]	2003	China	Cardia	ISH	FFPE	50	24	10	40
Xu et al[25]	2003	China	Gastric	ISH	FFPE	111	125	10	40
Ma et al[26]	2007	China	Gastric	PCR	FFPE	15	25	2	38
Ma et al[27]	2007	China	Cardia	PCR	FFPE	32	61	0	21
Rong et al[28]	2007	China	Cardia	PCR	FFPE	16	5	2	19
Wang et al[29]	2013	China	Gastric	PCR	FFPE	20	72	4	82
Su et al[15]	2015	China	Gastric	PCR	Other	1	14	0	15
Anwar et al[30]	1995	Japan	Gastric	PCR	FFPE	23	28	2	10
Erol et al[31]	2009	Turkey	Gastric	PCR	FFPE	17	21	33	73
Cândido et al[32]	2013	Brazil	Gastric	PCR	FFPE	4	36	10	30
Türkay et al[33]	2015	Turkey	Cardia	PCR	FFPE	2	17	0	8
Bozdayi et al[34]	2019	Turkey	Gastric	PCR	Other	20	33	5	21
Leon et al[35]	2019	Ethiopia	Cardia	PCR	FF	11	51	0	56

FF: Fresh frozen tissue; FFPE: Formalin-fixed paraffin-embedded tissue; ISH: In situ hybridization; NCa: Negative in cases; NCo: Negative in controls; PCa: Positive in cases; PCo: Positive in controls; PCR: Polymerase chain reaction.

Table 3 Subgroup analysis by nationality

		All	Chinese studies	Non-Chinese studies
All		5.80 (3.27-10.31) [60.0] <18>	7.86 (5.19-11.89) [0.0] <12>	1.97 (0.79-4.89) [56.8] <6>
Area
	Gastric	4.83 (2.64-8.83) [62.4] <14>	7.08 (4.60-10.89) [0.0] <10>	1.54 (0.60-3.92) [62.6] <4>
	Cardia	10.88 (5.42-21,8) [0.0] <5>	11.17 (5.34-23.35) [0.0] <3>	8.62 (0.88-84.8) [14.2] <2>
Sample
	FFPE	5.13 (2.55-10.34) [68.4] <12>	8.02 (4.74-13.6) [19.6] <8>	1.38 (0.45-4.16) [58.5] <4>
	FF	27.9 (3.70-211.7) <2>	31.0 (1.76-546.6) <1>	25.2 (1.45-439.1) <1>
Methods
	PCR	5.88 (3.00-11.52) [62.2] <16>	10.93 (6.44-18.5) [0.0] <10>	1.97 (0.79-4.98) [56.8] <6>
	ISH	6.23 (1.56-24.9) [64.0] <2>	6.23 (1.56-24.9) [64.0] <2>	-

Study: Summary odds ratio (95% confidence interval) [I² value (%)] <Number of selected studies>; FF: Fresh frozen tissue; FFPE: Formalin-fixed paraffin-embedded tissue; ISH: In situ hybridization; PCR: Polymerase chain reaction.

Table 4 Proportion of human papillomavirus positivity (%) by nationality

		Chinese studies	Non-Chinese studies
Total
	Positive/Observe	335/1225	127/511
	PP (95%CI)	27.3 (24.9-29.9)	24.9 (21.2-28.8)
Case
	Positive/Observe	298/711	77/263
	PP (95%CI)	41.9 (38.2-45.6)	29.3 (23.8-35.2)
Control
	Positive/Observe	37/514	50/248
	PP (95%CI)	7.2 (5.1-9.8)	20.2 (15.4-25.7)

PP: Human papillomavirus positivity.