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Table 4 Sample size calculations for prospective cohort study estimating a single UK-wide pyramid.

From: Methods for determining disease burden and calibrating national surveillance data in the United Kingdom: the second study of infectious intestinal disease in the community (IID2 study)

  England Wales
Organism/condition Baseline incidence1 Reduction to be detected Person-years GP practices Person-years GP practices
All IID 19.20% 20% 2,000 20 200 2
Severe cases* 6.00% 20% 7,000 70 400 4
Campylobacter 0.87% 20% 500,000 5,000 2,400 24
Salmonella 0.22% 20% 500,000 5,000 9,500 95
Campylobacter+Salmonella 1.10% 20% 200,000 2,000 2,000 20
Campylobacter+Salmonella+ C. perfringens 1.34% 20% 100,000 1,000 1,600 16
  Scotland Northern Ireland UK
Organism/condition Person-years GP practices Person-years GP practices Person-years GP practices
All IID 200 2 65 1 2,465 25
Severe cases* 700 7 300 3 8,400 84
Campylobacter 4,200 42 1,400 14 508,000 508
Salmonella 16,400 164 5,500 55 531,400 532
Campylobacter+Salmonella 3,400 34 1,200 12 206,600 207
Campylobacter+Salmonella+ C. perfringens 2,800 28 1,000 10 106,200 107
  1. * Severe cases are defined as those presenting to primary care
  2. Note: Based on ability to detect a 20% decrease in incidence with 80% power and 95% precision. Required number of person-years and GP practices (recruiting 100 patients from each practice) by country, based on the relative populations of the 4 UK countries