Table 1. Characteristics of the studies included in the meta-analysis.
| Study | Country | Period of enrolment | Study design | Study method | Tumor type | Sample size | No. of PTCs | PTC in HT, % |
|---|---|---|---|---|---|---|---|---|
| Chen 2013 [6] | Taiwan | 1998-2010 | cohort | Selective FNA | TC | 7605 | 19 | 0.92 |
| Isik 2010 [22] | Turkey | 2005-2009 | case-control | Selective FNA | TC | 500 | 5 | 0.67 |
| Mukasa 2011 [16] | Japan | 2006 | cohort | Selective FNA | PTC | 3688 | 52 | 1.77 |
| Anil 2010 [21] | Turkey | 2006-2009 | cohort | FNA | PTC | 715 | 21 | 1.22 |
| Azizi 2014 [4] | USA | 2010-2013 | case-control | FNA | TC | 2023 | 233 | 20.87 |
| de Alcantara-Jones 2015 [28] | Brazil | 2011 | case-control | FNA | PTC | 1049 | 33 | 5.20 |
| Fiore 2011 [8] | Italy | 2004-2009 | case-control | FNA | PTC | 9824 | 659 | 9.41 |
| Holm 1985 [26] | Sweden | 1959-1978 | cohort | FNA | PTC | 1658 | 2 | 0.12 |
| Matesa-Anic 2009 [23] | Croatia | 1995-2006 | case-control | FNA | PTC | 10508 | 269 | 1.95 |
| Ahn 2011 [3] | Korea | 2000-2005 | case-control | thyroidectomy | PTC | 303 | 269 | 96.67 |
| Bradly 2009 [5] | USA | 2000-2008 | case-control | thyroidectomy | PTC | 678 | 81 | 28.38 |
| Buyukasik 2011 [27] | Turkey | 1999-2006 | case-control | thyroidectomy | PTC | 917 | 61 | 11.69 |
| Consorti 2010 [7] | Italy | 1995-2008 | case-control | thyroidectomy | PTC | 404 | 101 | 36.23 |
| Gul 2010 [9] | Turkey | 2005-2008 | case-control | thyroidectomy | PTC | 613 | 193 | 45.65 |
| Kim 2011 [10] | Korea | 2003-2007 | case-control | thyroidectomy | PTC | 1277 | 1028 | 92.75 |
| Konturek 2013 [11] | Poland | 2002-2010 | cohort | thyroidectomy | PTC | 7545 | 636 | 23.45 |
| Kurukahvecioglu 2007 [12] | Turkey | 2001-2005 | case-control | thyroidectomy | PTC | 922 | 199 | 36.63 |
| Larson 2007 [13] | USA | 1987-2002 | case-control | thyroidectomy | PTC | 812 | 179 | 34.69 |
| Liu 2014 [14] | China | 2008-2013 | case-control | thyroidectomy | PTC | 6432 | 1722 | 43.75 |
| Lun 2013 [15] | China | 2004-2012 | case-control | thyroidectomy | PTC | 2478 | 676 | 49.61 |
| Mazokopakis 2010 [29] | Greece | 2005-2009 | case-control | thyroidectomy | PTC | 140 | 32 | 28.57 |
| McLeod 1988 [30] | USA | 1975-1985 | case-control | thyroidectomy | PTC | 793 | 143 | 23.44 |
| Paparodis 2014 [17] | USA | 1994-2013 | case-control | thyroidectomy | PTC | 2733 | 893 | 44.16 |
| Repplinger 2008 [31] | USA | 1994-2007 | case-control | thyroidectomy | PTC | 1198 | 293 | 29.03 |
| Siriweera 2010 [18] | Sri Lanka | Not specified | case-control | thyroidectomy | PTC | 5357 | 145 | 9.46 |
| Zhang 2012 [19] | China | 2008-2010 | case-control | thyroidectomy | PTC | 6109 | 2797 | 58.35 |
| Zhang 2014 [20] | China | 2004-2011 | case-control | thyroidectomy | PTC | 8524 | 1735 | 29.44 |
No., number; PTC, papillary thyroid carcinoma; HT, Hashimoto’s thyroiditis; FNA, fine-needle aspiration; TC, thyroid cancer.