Table 1. Characteristics of eligible studies included in the meta-analysis.
| First author | Year | Country | Ethnicity | Form of Disease | Sample size (Case/Control) | Distribution of genotypes and alleles |
Smoking status | Genotyping method | Quality scores | |||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Case |
Control |
|||||||||||||
| 5A/5A/5A/6A/6A/6A | 5A | 6A | 5A/5A/5A/6A/6A/6A | 5A | 6A | |||||||||
| Itagaki | 2004 | Japan | Asian | CP | 205/142 | 5/58/142 | 68 | 342 | 4/38/100 | 46 | 238 | Non-smokers | TaqMan | 31 |
| Itagaki | 2004 | Japan | Asian | AgP | 37/142* | 0/17/20 | 17 | 57 | 4/38/100 | 46 | 238 | Non-smokers | TaqMan | 31 |
| Astolfi | 2006 | Brazil | Mixed | CP | 90/103 | 19/52/19 | 90 | 90 | 8/70/25 | 86 | 120 | Non-smokers | PCR-RFLP | 29 |
| Kobayashi | 2009 | Japan | Asian | CP | 147/303 | — | 37 | 257 | — | 72 | 534 | S/N | DNA chip & PCR | 29 |
| Kobayashi | 2009 | Japan | Asian | AgP | 172/303* | — | 58 | 286 | — | 72 | 534 | S/N | DNA chip & PCR | 29 |
| Loo | 2011 | China | Asian | CP | 280/250 | 154/115/11 | 423 | 137 | 100/135/15 | 335 | 165 | Non-smokers | PCR-RFLP | 28 |
| Letra | 2012 | Brazil | Mixed | CP | 93/299 | — | 117 | 69 | — | 356 | 242 | S/N | TaqMan | 30 |
| Letra | 2012 | USA | Caucasian | CP | 67/202 | — | 78 | 56 | — | 193 | 211 | S/N | TaqMan | 30 |
| Li | 2012 | China | Asian | CP | 122/532 | 75/44/3 | 194 | 50 | 213/283/36 | 709 | 355 | S/N | PCR-RFLP | 27 |
CP, chronic periodontitis; AgP, aggressive periodontitis; S/N, smokers and nonsmokers.
*The control group for AgP used the same subjects as the control group for CP. In the pooled analysis, the CP and AgP cases were combined into one group and the control group was counted only one time.