To evaluate CT abnormalities in the lung parenchyma in close contacts at high risk for developing multidrug- or extensively drug-resistant Tb by using a follow-up ultralow dose CT scan.

Multidrug- or extensively resistant tuberculosis tuberculosis is a major public health threat worldwide and the global burden of drug-resistant tuberculosis is increasing. Drug-resistant tuberculosis is associated with long period and high costs for treatment, high rates of default, treatment failure and death.

Drug-resistant tuberculosis should be diagnosed rapidly so as to reduce potential transmission. In the United States, at least one-fifths cases of multidrug-resistant tuberculosis can be linked to transmission. Close contacts to drug-resistant tuberculosis are at high risk for being transmitted and developing drug-resistant tuberculosis. There are two options suggested for close contacts to drug-resistant tuberculosis: preventive therapy and close observation. But both strategies are lack of sufficient evidence.

Ultralow chest CT scan may be an alternative for early identification and risk stratification of developing active tuberculosis in close contacts to drug-resistant tuberculosis with minimal radiation exposure similar to that of chest x-ray.

Inclusion Criteria:

• Individuals who had household contact with or who had worked in the same rooms as patients with smear-positive, culture-proven multidrug-or extensively drug-resistant pulmonary tuberculosis for longer than 8 hours per day
• Older than 20 years

Exclusion Criteria:

• Pregnant women
• Individuals with abnormality on chest x-ray suspected of active tuberculosis