Impaired or attenuated cell mediated immunity (CMI) can potentially cause a false negative tuberculin reaction. Many factors have been reported to cause a decreased ability to respond to the tuberculin test in the presence of tuberculous infection including viral infections (e.g., measles, mumps, chickenpox and HIV), live virus vaccinations (e.g., measles, mumps, rubella, oral polio and yellow fever), overwhelming tuberculosis, other bacterial infections, leukemia, sarcoidosis, fungal infections, metabolic derangements, low protein states, diseases affecting lymphoid organs, drugs (corticosteroids and many other immunosuppressive agents), and malignancy or stress. (8) (17) (18) A TST should be deferred for patients with major viral infections or live-virus vaccination in the past month. Persons with the common cold may be tuberculin tested.
Because TST results in HIV-infected individuals are less reliable as CD4 counts decline, screening should be completed as early as possible after HIV-infection occurs. (18)