Latent TB Infection: Diagnosis of Latent TB Infection

Latent TB Infection: Guide for Diagnosis and Treatment

Diagnosis of Latent TB Infection

The diagnosis of LTBI is based on information gathered from the medical history, TST or IGRA result, chest radiograph, physical examination, and in certain circumstances, sputum examinations. The presence of TB disease must be excluded before treatment for LTBI is initiated because failure to do so may result in inadequate treatment and development of drug resistance.

CDC discourages use of diagnostic tests for LTBI among individuals and populations at low risk for infection with M. tuberculosis. Despite CDC recommendations to the contrary, testing is sometimes done to meet administrative or legal requirements for groups who are not considered to have an increased possibility of infection in the absence of other factors cited above, such as persons meeting entrance requirements for certain schools and workplaces.

Evaluation of Persons with Positive TB Test Results

Differentiating Between Latent TB Infection and TB Disease

LTBI

• No symptoms or physical findings suggestive of TB disease.
• TST or IGRA result usually positive.
• Chest radiograph is typically normal.
• If done, respiratory specimens are smear and culture negative.
• Cannot spread TB bacteria to others.
• Should consider treatment for LTBI to prevent TB disease.

TB Disease

• Symptoms may include one or more of the following: fever, cough, chest pain, weight loss, night sweats, hemoptysis, fatigue, and decreased appetite.
• TST or IGRA result usually positive.
• Chest radiograph is usually abnormal. However, may be normal in persons with advanced immunosuppression or extrapulmonary disease.
• Respiratory specimens are usually smear or culture positive. However, may be negative in persons with extrapulmonary disease or minimal or early pulmonary disease.
• May spread TB bacteria to others.
• Needs treatment for TB disease.