Summary frequencies of tumour MLH1 promoter methylation
| Sample group* | Number of studies | Positive MLH1 promoter methylation | Negative MLH1 promoter methylation | MLH1 promoter methylation frequency (95% CI) |
| Known positive MMR mutation status | ||||
| All MMR mutation carriers | 29 | 58 | 388 | 15.56% (9.17% to 23.27%) |
| MLH1 mutation carriers | 22 | 39 | 250 | 16.68% (8.58% to 26.81%) |
| MLH1 mutation carriers (A region tested) | 7 | 21 | 88 | 41.59% (13.80% to 72.71%) |
| MLH1 mutation carriers (C region tested) | 12 | 8 | 183 | 5.56% (2.21% to 10.30%) |
| Known negative MMR mutation status | ||||
| MSI-H, A region tested | 7 | 61 | 82 | 39.67% (17.70% to 64.11%) |
| MSI-H, C region tested | 12 | 363 | 317 | 47.07% (30.84% to 63.62%) |
| MSI-H, A region tested MLH1 deficiency IHC | 5 | 42 | 66 | 31.92% (7.30% to 63.99%) |
| MSI-H, C region tested MLH1 deficiency IHC | 8 | 121 | 164 | 39.81% (13.50% to 69.83%) |
| MSS, A region tested | 4 | 53 | 259 | 16.54% (10.41% to 23.77%) |
| MSS, C region tested | 2 | 3 | 466 | 0.06% (0.00% to 2.19%) |
↵* In some primary references, the A region is termed the 5′ region, and the C region is termed the 3′ region.