| Age <6 months |
| Age >65 yrs 137 |
| Cellular immune defects (e.g. HIV infection, AIDS and lymphoproliferative disorders)</emph> |
| Acute or recent severe viral infection (e.g. rubella 138, measles 139, 140 and mononucleosis 140) and scarlet fever 140 |
| Immunisation with live vaccines within the past 6 weeks (e.g. measles, poliomyelitis, yellow fever, mumps 141 and rubella 142</emph>) |
| Severe debilitating diseases (e.g. malignancies 143</emph>) |
| Systemic high-dose corticosteroid therapy (>15 mg prednisolone equivalent) or treatment with immunosuppressants |
| Advanced pulmonary tuberculosis 133, 144, central nervous system tuberculosis and disseminated tuberculosis 145 |
| Sarcoidosis 146 |
| Malnutrition 147 |
| Window period for manifest immune response to infection with Mycobacterium tuberculosis |
| Application errors (incomplete or subcutaneous tuberculin injection, incorrect quantity of tuberculin, inadequate storage of tuberculin) |
| Reading errors (too early or too late) |