| First author, year | Number of cases | Number of controls | Number of cases with HP (+), (%) | Number of controls with HP (+), (%) | OR (95% CI) |
| Frigo, 1998 [16] | 105 | 129 | 95 (90.5) | 60 (46.5) | 10.93 (5.22, 22.85) | Perez-Perez, 1999 [18] | 42 | 47 | 8 (19.1) | 12 (25.5) | 0.69 (0.25, 1.89) |
Koćak, 1999 [17] | 95 | 116 | 87 (91.5) | 52 (44.8) | 13.38 (5.95, 30.13) | Hayakawa, 2000 [19] | 34 | 29 | 18 (52.9) | 6 (20.6) | 4.31 (1.40, 13.25) |
Sahin, 2000 [20] | 60 | 60 | 37 (61.7) | 32 (53.3) | 1.41 (0.68, 2.91) | Reymunde, 2001 [21] | 45 | 44 | 40 (89.0) | 3 (7.0) | 109.33 (24.49, 488.12) | Kazerooni, 2002 [24] | 54 | 53 | 44 (81.5) | 29 (54.7) | 3.64 (1.52, 8.73) | Bagis, 2002 [23] | 20 | 10 | 19 (95.0) | 5 (50.0) | 19.00 (1.79, 201.68) | Erdem, 2002 [22] | 47 | 39 | 40 (85.1) | 25 (64.1) | 3.20 (1.14, 9.02) | Berker, 2003 [27] | 80 | 80 | 56 (70.0) | 49 (61.2) | 1.48 (0.77, 2.85) | Jacobson, 2003 [26] | 53 | 153 | 19 (35.7) | 45 (29.7) | 1.34 (0.69, 2.60) |
Salimi-Khayati, 2003 [25] | 54 | 54 | 48 (88.9) | 22 (40.7) | 11.64 (4.25, 31.87) | Karaca, 2004 [31] | 56 | 90 | 46 (82.1) | 58 (64.4) | 2.54 (1.13, 5.70) | Cevrioglu, 2004 [30] | 27 | 97 | 23 (85.2) | 71 (73.2) | 2.11 (0.66, 6.67) | Xia, 2004 [29] | 72 | 100 | 64 (88.9) | 45 (45.0) | 9.78 (4.25, 22.51) | Jamal, 2004 [28] | 39 | 55 | 26 (66.7) | 23 (41.8) | 2.78 (1.18, 6.54) | Lee, 2005 [32] | 40 | 42 | 26 (65.0) | 28 (66.7) | 0.93 (0.37, 2.31) | Karadeniz, 2006 [34] | 31 | 29 | 21 (67.7) | 23 (79.3) | 0.55 (0.17, 1.77) | Özcimen, 2006 [33] | 70 | 70 | 35 (50.0) | 33 (47.1) | 1.12 (0.58, 2.18) | Tuncel, 2006 [35] | 50 | 88 | 48 (96.0) | 73 (82.9) | 4.93 (1.08, 22.54) | Hatziveis, 2007 [38] | 25 | 85 | 14 (56.0) | 41 (48.2) | 1.37 (0.56, 3.35) | Güney, 2007 [37] | 25 | 20 | 20 (80.0) | 10 (50.0) | 4.00 (1.07, 14.90) | Aytac, 2007 [36] | 52 | 55 | 22 (42.3) | 22 (40.0) | 1.10 (0.51, 2.38) | Sandven, 2008 [39] | 244 | 244 | 105 (43.0) | 58 (23.8) | 2.42 (1.64, 3.57) | Mansour, 2009 [40] | 50 | 50 | 42 (84.0) | 18 (36.0) | 9.33 (3.60, 24.17) | Guven, 2011 [5] | 40 | 40 | 32 (80.0) | 14 (35.0) | 7.43 (2.70, 20.42) | Mansour, 2011 [4] | 80 | 80 | 71 (88.8) | 24 (30.0) | 18.41 (7.93, 42.74) | Bezircioğlu, 2011 [3] | 36 | 36 | 8 (22.2) | 1 (2.8) | 10.00 (1.18, 84.78) | Epstein, 2012 [41] | 23 | 59 | 16 (69.6) | 38 (64.4) | 1.26 (0.45, 3.56) | Vikanes, 2013 [43] | 62 | 108 | 38 (61.3) | 67 (62.0) | 0.97 (0.51, 1.84) |
Güngören, 2013 [42] | 90 | 50 | 75 (83.3) | 30 (60.0) | 3.33 (1.51, 7.36) | Shaban, 2014 [6] | 50 | 50 | 46 (92.0) | 28 (56.0) | 9.04 (2.82, 28.95) |
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