Table 9. Estimated prevalence (probability) of genetic susceptibility in rheumatoid arthritis, ankylosing spondylitis, and systemic lupus erythematosus.
| Prevalence ‡ | MZ-TwinConcordance * | % Susceptible | |
| P(D) | P(D|MZD) | P(G) | |
| Rheumatoid Arthritis | 1 – 2% | ∼ 35% | 5.7 – 11.4% |
| Ankylosing Spondylitis | 0.4 – 4% | ∼ 53% | 1.4 – 15% |
| Systemic Lupus Erythematosus | ∼ 0.025% | ∼ 39% | ∼ 0.13% |
‡
The prevalence of diseases {P(D)} is from data provided in Reference [35].
*
Studies [36]-[38] report pair-wise MZ-twin concordance-rates. These have been converted into proband-wise rates {P(D|MZD)} assuming a random sampling of twin-pairs [30]. Also, the IU environment has been assumed to have no impact on the disease. A violation of either of these assumptions will make the estimate of P(G) too low.