Multivariable model predicting false positives
| Population characteristic | Level | OR (95% CI) N=32 195 |
| Age (years) | 1-year increase | 1.01 (1.01 to 1.01) |
| Gender | Female | 1.05 (1.01 to 1.10 |
| Comorbidity | Cardiovascular disease | 1.04 (0.86 to 1.26) |
| Chronic respiratory disease | 1.31 (1.22 to 1.40) | |
| Diabetes | 0.84 (0.77 to 0.93) | |
| Hypertension | 0.97 (0.90 to 1.05) | |
| Immunosuppression (including steroid use) | 1.49 (1.36 to 1.64) | |
| Active malignancy | 1.25 (0.97 to 1.61) | |
| Renal impairment | 1.52 (1.17 to 1.97) | |
| Smoker | 1.10 (1.04 to 1.16) | |
| Stroke | 1.23 (0.87 to 1.75) | |
| Number of drugs used | 0 | Reference |
| 1–5 | 1.13 (1.06 to 1.21) | |
| 6–10 | 1.60 (1.42 to 1.81) | |
| 11 or more | 2.36 (1.82 to 3.07) | |
| Deprivation index | 1–2 | Reference |
| 3–4 | 0.95 (0.89 to 1.02) | |
| 5–6 | 0.95 (0.89 to 1.03) | |
| 7–8 | 0.99 (0.92 to 1.07) | |
| 9–10 | 1.05 (0.97 to 1.14) | |
| Number of 111 contacts in study period | 1 | Reference |
| 2 | 0.86 (0.78 to 0.95) | |
| 3 or more | 0.71 (0.58 to 0.88) |