TABLE 1.
Risk factors for the development of active tuberculosis (TB) among individuals with a positive tuberculin skin test (TST) (presumed infected with Mycobacterium tuberculosis)
| Risk factor | Estimated risk for TB* |
|---|---|
| High risk | |
| AIDS | 110–170 |
| HIV | 50–110 |
| Transplantation (related to immune-suppressant therapy) | 20–74 |
| Silicosis | 30 |
| Chronic renal failure requiring hemodialysis | 7–50 |
| Carcinoma of head and neck | 11.6 |
| Recent TB infection (≤2 years) | 15.0 |
| Abnormal chest x-ray – fibronodular disease | 6–19 |
| Moderate risk | |
| Tumour necrosis factor alpha inhibitors | 1.5–5.8 |
| Diabetes mellitus (all types) | 2–3.6 |
| Treatment with glucocorticoids (≥15 mg/day prednisone) | 4.9 |
| Young age when infected (0–4 years) | 2.2–5 |
| Slightly increased risk | |
| Heavy alcohol consumption (≥3 drinks/day) | 3–4 |
| Underweight (<90% ideal body weight; for most people, this is a body mass index ≤20 kg/m2) | 2–3 |
| Cigarette smoker (1 pack/day) | 1.8–3.5 |
| Abnormal chest x-ray – granuloma | 2 |
| Low risk | |
| Person with positive TST, no known risk factor, normal chest x-ray (‘low risk reactor’) | 1 |
| Very low risk | |
| Person with positive two-step TST (booster), no other known risk factor and normal chest x-ray | 0.5 |
*
Relative to people with no known risk factor. Adapted from Can Respir J 2013; 20 (SA): 45A