Determining Non-Infectiousness in Disseminated TB Patients

General Principles of TB Infectiousness

The American Thoracic Society recommends that TB infectiousness is primarily associated with pulmonary or laryngeal TB, as transmission occurs through aerosolized droplet nuclei produced by coughing, sneezing, speaking, or singing 2
Disseminated TB with pulmonary involvement follows the same principles of infectiousness as pulmonary TB 2

After starting standard multi-drug therapy, the concentration of viable M. tuberculosis in sputum decreases by more than 90% during the first 2 days of treatment, and more than 99% by days 14-21 of treatment, according to the American Journal of Respiratory and Critical Care Medicine 2
After 14-21 days of treatment, infectiousness averages less than 1% of the pretreatment level, as stated by the American Thoracic Society/CDC/Infectious Diseases Society of America guidelines 1, 2

The American Thoracic Society/CDC/Infectious Diseases Society of America guidelines state that a patient with TB is considered non-infectious when they have received standard multi-drug anti-TB therapy for 2-3 weeks, demonstrate complete adherence to treatment, show evidence of clinical improvement, have negligible likelihood of multi-drug-resistant TB, and all close contacts have been identified, evaluated, and managed appropriately 1, 2

Patients in hospitals or congregate settings require three consecutive AFB-negative sputum smear results collected 8-24 hours apart, with at least one specimen being an early-morning specimen, as recommended by the American Thoracic Society/CDC/Infectious Diseases Society of America guidelines 2
All patients with suspected or proven multi-drug-resistant TB should be subjected to more stringent criteria for determining absence of infectivity and remain in isolation until they have three consecutive negative sputum smears, according to the American Thoracic Society/CDC/Infectious Diseases Society of America guidelines 1, 2

The determination of non-infectiousness should be individualized based on extent of illness, presence of cavitary pulmonary disease, degree of positivity of sputum AFB smear results, frequency and strength of cough, likelihood of drug-resistant organisms, and nature and circumstances of contact with others, as stated by the American Thoracic Society/CDC/Infectious Diseases Society of America guidelines 2