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# Table 2 Distribution of unique study identification numbers between cancer registry and hospital separations.

Study identification numbers Cancer registry present Cancer registry absent Totals
Hospital separations present a b (a + b)
Hospital separations absent c d (c + d)
Total (a + c) (b + d) (a + b + c + d)
1. Notes.
2. 1. Total unique study identification numbers = (a + b + c)
3. 2. All study identification numbers from BCCA cancer incidence registry = (a + c)
4. 3. All study identification numbers from hospital cancer separations = (a + b)
5. 4. Shared study identification numbers between BCCA registry and hospital separations = a
6. 5. Study identification numbers only in the BCCA registry = b
7. 6. Study identification numbers only in hospital separations = c
8. 7. Reference population used for annual calculations is the mid-year VIHA population = (a + b + c + d)
9. 8. Count "d" represents the balance of the VIHA mid-year population appearing in neither registry nor separations records
10. 9. In the case of the 1990–1999 aggregate file, the ten-year mean mid-year population is designated as the reference population; see discussion in text for effect of this assumption
11. 10. The cancer registry is taken as the gold standard
12. Measures.
13. 1. Similarity = [(a + b)/(a + c)]
14. 2. Sensitivity = [a/(a + c)]
15. 3. Specificity = [d/(b + d)]
16. 4. Positive predictive value = [a/(a + b)]
17. 5. Negative predictive value = [d/(c + d)]