Table 3. Performance ratios with the improved Farrington method as reference, adjusted for past and current outbreaks (duration and amplitude), trend, seasonality, dispersion and baseline frequency (α = 0.01 for Improved Farrington, Original Farrington, Periodic Poisson GLM and Neg Binomial GLM, CDC and EARS C1-C3. α = 0.05 for Bayes 1-3).
| Covariates | Categories/values | FPR ratio⋆ (CI 95%) | Specificity ratio⋆ (CI 95%) | POD ratio⋆ (CI 95%) | POD1week ratio⋆ (CI 95%) | Sensitivity ratio⋆ (CI 95%) |
|---|---|---|---|---|---|---|
| Methods | Improved Farrington | Ref (-) | Ref (-) | Ref (-) | Ref (-) | Ref (-) |
| Original Farrington | 2.43 (2.38 - 2.49) | 0.99 (0.99 - 9.99) | 1.32 (1.31 - 1.32) | 1.34 (1.33 - 1.35) | 1.42 (1.41 - 1.42) | |
| Periodic Poisson GLM | 3.43 (3.35 - 3.50) | 0.98 (0.98 - 0.98) | 1.57 (1.56 - 1.58) | 1.67 (1.66 - 1.68) | 1.74 (1.73 - 1.75) | |
| Periodic Neg Binomial GLM | 0.71 (0.68 - 0.73) | 1.00 (1.00 - 1.00) | 1.03 (1.03 - 1.04) | 1.07 (1.06 - 1.08) | 1.01 (1.00 - 1.02) | |
| CDC | 3.79 (3.71 - 3.87) | 0.96 (0.96 - 0.96) | 1.04 (1.03 - 1.05) | 0.55 (0.55 - 0.55) | 1.67 (1.66 - 1.68) | |
| CUSUM | 45.79 (44.90 - 46.70) | 0.53 (0.53 - 0.53) | 1.86 (1.85 - 1.87) | 2.07 (2.06 - 2.08) | 3.69 (3.67 - 3.71) | |
| CUSUM Rossi | 41.08 (40.28 - 41.90) | 0.58 (0.58 - 0.58) | 1.78 (1.77 - 1.79) | 1.94 (1.93 - 1.95 | 3.51 (3.49 - 3.53) | |
| CUSUM GLM | 45.95 (45.06 - 46.87) | 0.53 (0.52 - 0.53) | 1.95 (1.94 - 1.96) | 2.17 (2.16 - 2.18) | 3.89 (3.87 - 3.91) | |
| CUSUM GLM Rossi | 41.50 (40.69 - 42.32) | 0.57 (0.57 - 0.57) | 1.87 (1.87 - 1.88) | 2.04 (2.03 - 2.05) | 3.72 (3.70 - 3.74) | |
| Bayes 1 | 10.48 (10.27 - 10.70) | 0.91 (0.91 - 0.91) | 1.76 (1.75 - 1.77) | 1.95 (1.93 - 1.96) | 1.91 (1.90 - 1.92) | |
| Bayes 2 | 9.74 (9.54 - 9.94) | 0.92 (0.92 - 0.92) | 1.87 (1.86 - 1.88) | 2.04 (2.03 - 2.05) | 2.23 (2.22 - 2.24) | |
| Bayes 3 | 11.58 (11.35 - 11.82) | 0.90 (0.90 - 0.90) | 1.93 (1.92 - 1.94) | 2.11 (2.10 - 2.13) | 2.53 (2.52 - 2.55) | |
| RKI 1 | 8.60 (8.42 - 8.78) | 0.93 (0.93 - 0.93) | 1.57 (1.56 - 1.57) | 1.73 (1.72 - 1.74) | 1.49 (1.48 - 1.50) | |
| RKI 2 | 5.77 (5.65 - 5.89) | 0.96 (0.96 - 0.96) | 1.57 (1.56 - 1.58) | 1.70 (1.69 - 1.71) | 1.69 (1.68 - 1.70) | |
| RKI 3 | 7.30 (7.15 - 7.45) | 0.94 (0.94 - 0.94) | 1.65 (1.64 - 1.66) | 1.78 (1.77 - 1.79) | 2.04 (2.03 - 2.05) | |
| GLR Negative Binomial | 4.49 (4.40 - 4.59) | 0.97 (0.97 - 0.97) | 1.17 (1.17 - 1.18) | 0.87 (0.87 - 0.88) | 1.06 (1.05 - 1.06) | |
| GLR Poisson | 16.15 (15.83 - 16.47) | 0.85 (0.85 - 0.85) | 1.75 (1.74 - 1.75) | 1.77 (1.76 - 1.78) | 2.24 (2.23 - 2.25) | |
| EARS C1 | 7.16 (7.01 - 7.31) | 0.95 (0.95 - 0.95) | 1.54 (1.53 - 1.55) | 1.69 (1.68 - 1.70) | 1.25 (1.24 - 1.26) | |
| EARS C2 | 8.85 (8.67 - 9.04) | 0.93 (0.93 - 0.93) | 1.57 (1.56 - 1.58) | 1.68 (1.67 - 1.69) | 1.90 (1.89 - 1.91) | |
| EARS C3 | 7.74 (7.59 - 7.91) | 0.94 (0.94 - 0.94) | 1.25 (1.25 - 1.26) | 0.25 (0.25 - 0.25) | 1.73 (1.72 - 1.74) | |
| OutbreakP | 62.32 (61.10 - 63.56) | 0.38 (0.38 - 0.38) | 1.63 (1.62 - 1.64) | 2.00 (1.98 - 2.01) | 3.23 (3.21 - 3.25) | |
| k1 | 0 | Ref (-) | Ref (-) | Ref (-) | Ref (-) | Ref (-) |
| 2 | 0.99 (0.98 - 0.99) | 1.00 (1.00-1.00) | 0.99 (0.99 - 0.99) | 0.99 (0.99 - 0.99) | 0.99 (0.99-0.99) | |
| 3 | 0.98 (0.98 - 0.99) | 1.00 (1.00-1.00) | 0.98 (0.98 - 0.98) | 0.98 (0.98 - 0.98) | 0.98 (0.98-0.98) | |
| 5 | 0.98 (0.97 - 0.98) | 1.01 (1.01-1.01) | 0.97 (0.97 - 0.97) | 0.97 (0.97 - 0.97) | 0.96 (0.96-0.97) | |
| 10 | 0.96 (0.96 - 0.96) | 1.01 (1.01-1.01) | 0.94 (0.94 - 0.94) | 0.93 (0.93 - 0.94) | 0.93 (0.93-0.93) | |
| k2 | 1 | - - | Ref (-) | Ref (-) | Ref (-) | Ref (-) |
| 2 | - - | 1.00 (1.00 - 1.00) | 1.32 (1.32 - 1.32) | 1.30 (1.30 - 1.30) | 1.23 (1.23 - 1.23) | |
| 3 | - - | 1.00 (1.00 - 1.00) | 1.63 (1.63 - 1.64) | 1.64 (1.64 - 1.64) | 1.47 (1.47 - 1.48) | |
| 4 | - - | 1.00 (1.00 - 1.00) | 1.93 (1.93 - 1.94) | 2.01 (2.00 - 2.01) | 1.73 (1.73 - 1.73) | |
| 5 | - - | 1.00 (0.99 - 1.00) | 2.22 (2.21 - 2.22) | 2.39 (2.38 - 2.40) | 1.99 (1.98 - 1.99) | |
| 6 | - - | 0.99 (0.99 - 0.99) | 2.47 (2.47 - 2.48) | 2.76 (2.75 - 2.77) | 2.23 (2.22 - 2.24) | |
| 7 | - - | 0.99 (0.99 - 0.99) | 2.69 (2.68 - 2.70) | 3.10 (3.09 - 3.11) | 2.44 (2.44 - 2.45) | |
| 8 | - - | 0.99 (0.99 - 0.99) | 2.85 (2.84 - 2.86) | 3.37 (3.36 - 3.39) | 2.62 (2.61 - 2.63) | |
| 9 | - - | 0.99 (0.99 - 0.99) | 2.95 (2.94 - 2.95) | 3.57 (3.56 - 3.58) | 2.75 (2.74 - 2.76) | |
| 10 | - - | 0.99 (0.99 - 0.99) | 2.96 (2.95 - 2.97) | 3.67 (3.65 - 3.68) | 2.82 (2.81 - 2.83) | |
| Trend | No (β = 0) | Ref (-) | Ref (-) | Ref (-) | Ref (-) | Ref (-) |
| Yes (β ≠ 0) | 2.75 (2.74 - 2.76) | 0.84 (0.84 - 0.84) | 1.17 (1.16 - 1.17) | 1.28 (1.28 - 1.28) | 1.20 (1.20 - 1.20) | |
| Seasonality (m) | No (m = 0) | Ref (-) | Ref (-) | Ref (-) | Ref (-) | Ref (-) |
| Annual (m = 1) | 1.06 (1.06 - 1.06) | 0.99 (0.99 - 0.99) | 0.97 (0.97 - 0.97) | 0.98 (0.98 - 0.98) | 0.97 (0.97 - 0.97) | |
| Biannual (m = 2) | 1.13 (1.12 - 1.13) | 0.98 (0.98 - 0.98) | 0.92 (0.92 - 0.92) | 0.93 (0.93 - 0.93) | 0.92 (0.92 - 0.92) | |
| Dispersion (ϕ) | 1 | Ref (-) | Ref (-) | Ref (-) | Ref (-) | Ref (-) |
| 1.1 | 1.02 (1.02 - 1.02) | 1.00 (1.00 - 1.00) | 1.00 (1.00 - 1.00) | 1.00 (1.00 - 1.00) | 1.00 (1.00 - 1.00) | |
| 1.2 | 1.04 (1.04 - 1.04) | 1.00 (1.00 - 1.00) | 1.00 (1.00 - 1.00) | 1.00 (1.00 - 1.00) | 0.99 (0.99 - 0.99) | |
| 1.5 | 1.07 (1.06 - 1.07) | 0.99 (0.99 - 0.99) | 0.99 (0.99 - 1.00) | 1.00 (1.00 - 1.00) | 0.98 (0.98 - 0.98) | |
| 2 | 1.08 (1.08 - 1.08) | 0.99 (0.99 - 0.99) | 0.99 (0.99 - 0.99) | 1.00 (1.00 - 1.00) | 0.98 (0.97 - 0.98) | |
| 3 | 1.08 (1.08 - 1.08) | 0.98 (0.98 - 0.98) | 0.98 (0.98 - 0.98) | 1.01 (1.01 - 1.01) | 0.98 (0.98 - 0.99) | |
| 5 | 1.07 (1.07 - 1.08) | 0.97 (0.97 - 0.97) | 1.09 (1.09 - 1.09) | 1.16 (1.16 - 1.17) | 1.11 (1.11 - 1.11) | |
| Frequency (θ) | -2 (0, 14 cases) | Ref (-) | Ref (-) | Ref (-) | Ref (-) | Ref (-) |
| 0.1 (1.1 cases) | 1.14 (1.14 - 1.14) | 0.99 (0.99 - 0.99) | 1.01 (0.93 - 0.94) | 1.03 (1.03 - 1.03) | 0.95 (0.94 - 0.95) | |
| 0.5 (1.65 cases) | 1.18 (1.18 - 1.19) | 0.98 (0.98 - 0.98) | 1.01 (1.01 - 1.01) | 1.04 (1.04 - 1.04) | 0.94 (0.94 - 0.94) | |
| 1.5 (4.48 cases) | 1.27 (1.25 - 1.28) | 0.97 (0.97 - 0.98) | 1.02 (1.02 - 1.03) | 1.07 (1.07 - 1.08) | 0.92 (0.92 - 0.93) | |
| 2.5 (12.18 cases) | 1.22 (1.19 - 1.26) | 0.98 (0.98 - 0.98) | 1.03 (1.03 - 1.04) | 1.10 (1.10 - 1.10) | 0.90 (0.89 - 0.90) | |
| 3.75 (42.52 cases) | 0.88 (0.84 - 0.93) | 1.02 (1.02 - 1.02) | 1.04 (1.04 - 1.04) | 1.10 (1.10 - 1.10) | 0.84 (0.84 - 0.84) | |
| 5 (148.41 cases) | 0.38 (0.34 - 0.42) | 1.13 (1.13 - 1.13) | 1.03 (1.03 - 1.03) | 1.04 (1.04 - 1.04) | 0.77 (0.77 - 0.77) |
⋆ Each ratio was statistically significant with p ≤ 10e − 3.