Table 5.
Sample size estimates for GP Presentation Study estimating a single UK-wide pyramid.
| England | Wales | |||||
|---|---|---|---|---|---|---|
| Organism | Baseline incidence* | Reduction to be detected | Person-years | GP practices | Person-years | GP practices |
| Campylobacter | 4.10% | 20% | 115,000 | 20 | 7,000 | 2 |
| Salmonella | 0.16% | 50% | 41,000 | 7 | 3,000 | 1 |
| Salmonella | 0.16% | 40% | 67,000 | 12 | 4,000 | 1 |
| Salmonella | 0.16% | 30% | 127,000 | 22 | 8,000 | 2 |
| Salmonella | 0.16% | 20% | 302,000 | 51 | 18,000 | 3 |
| C. perfringens | 0.13% | 20% | 364,000 | 61 | 22,000 | 4 |
| Scotland | Northern Ireland | UK | ||||
| Organism | Person-years | GP practices | Person-years | GP practices | Person-years | GP practices |
| Campylobacter | 12,000 | 2 | 4,000 | 1 | 138,000 | 25 |
| Salmonella | 5,000 | 1 | 2,000 | 1 | 51,000 | 10 |
| Salmonella | 7,000 | 2 | 3,500 | 1 | 81,500 | 16 |
| Salmonella | 13,000 | 3 | 4,500 | 1 | 152,500 | 28 |
| Salmonella | 31,000 | 6 | 10,500 | 2 | 361,500 | 62 |
| C. perfringens | 38,000 | 7 | 13,000 | 3 | 434,500 | 75 |
* Incidence of GP presentation in original IID study
Note: Based on the ability to detect at least a 20% reduction in incidence with 90% power and 95% precision. Required number of person-years and GP practices (assuming an average GP practice size of 6,000 patients) by country, based on the relative populations of the 4 countries.