Table 1. Epidemiologic measures of association and observable effect measures in longitudinal syndromic surveillance studies.
| Measures | T = t | T = Σti(i = 0, 1, …, I; I ≠ t) |
|---|---|---|
| Syndromic cases | a(t) | A(t0, tI) = Σa(ti) |
| Total patients seen without syndrome | b(t) | B(t0, tI) = Σb(ti) |
| Source population | N1(t) | N0(t0, tI) |
| Diagnostic outcome proportion | a(t)∕[a(t) + b(t)] | A(t0, tI)∕[A(t0, tI) + B(t0, tI)] |
| Incidence rate (hazard) | a(t)∕N1(t) | A(t0, tI)∕N0(t0, tI) |
| Hazard rate ratio (empirical) | [a(t)∕N1(t)]∕[A(t0, tI)∕N0(t0, tI)] | |
| Proportionate diagnostic outcome ratio (PDOR) | {a(t)∕[a(t) + b(t)]}∕{A(t0, tI)∕[A(t0, tI) + B(t0, tI)]} | |
Notes.
- T
- time
- i
- time points