Table 1: Characteristics of the included studies on Helicobacter pylori infection and risk of lung cancer.

First author, yearCountryDiagnosisStudy sizeNumberQR
H. pylori infectionLung cancerCases (H. pylori +)Controls (H. pylori +)

Gocyk, 2000 [14]#PolandAA15050 (45)100 (64)7
Philippou, 2004 [17]#GreeceAA14072 (44)68 (38)7
Ece, 2005 [13]#TurkeyAA7143 (40)28 (12)6
Najafizadeh, 2007 [16]#IranaA8034 (21)35 (18)8
Kosunen, 2009 [15]*FinlandaNR26,705NANA7
Behroozian, 2010 [12]#IranaA13266 (48)66 (34)5
Koshiol, 2012 [3]$FinlandaB1,389696 (550)693 (544)9

Case-control study; *prospective study; $nested case-control study.
NR: not reported; NA: not applicable; QR: quality rating according to New castle-Ottawa Scale;
H. pylori +: number of patients with seropositivity of H. pylori.
a: Enzyme-Linked Immunosorbent Assay.
A: histologically conformed; B: registry based.