- Evidence of tuberculosis as documented by a specific assay, medical history, and chest x-ray. A specific assay, e.g., tuberculin testing, will be conducted unless it is medically inappropriate. Exceptions include patients with a history of a positive specific assay for TB who have been treated with isonicotinyl hydrazine (documented) for at least 6 months, or patients with a previous diagnosis of TB who have been appropriately treated and can provide documentation.