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TB Diagnosis and Treatment (For Clinicians)

Tuberculosis (TB) in Wisconsin is rare. The majority of people with TB in Wisconsin acquire the infection outside of Wisconsin. Diagnosis and treatment of TB disease or latent tuberculosis infection (LTBI) should start with a risk assessment, symptom evaluation, and testing.

Symptoms are usually present for active TB disease, but are absent for latent TB infection.

The use of tuberculin skin test (TST) or interferon gamma release assay (IGRA) blood test can aid in diagnosing TB infection, but cannot differentiate between latent infection and active TB disease.

Medical evaluation, radiography, and the collection of specimens for microbiology are often needed to complete the diagnosis.

People with clinical signs and symptoms of TB disease, but negative IGRA or TST, should still be evaluated, especially if TB risk factors are present.

Doctor holding clipboard with papers discussing medical form with patient

Please see the CDC (Centers for Disease Control and Prevention) Tuberculosis webpage for detailed information and published guidelines on diagnosis and treatment.

The Wisconsin TB Program encourages clinicians to use the resources below for the diagnosis and treatment of TB disease or LTBI.

State and local public health departments are responsible for ensuring that adequate and appropriate TB diagnostic and treatment services are accessed. They monitor the results of therapy and provide consultation, education, and care management for persons with suspect or active TB disease and latent TB infection (LTBI).

In collaboration with the medical provider, public health departments provide the following services for all persons with suspect or active TB disease and LTBI:

  • Facilitation of comprehensive TB patient evaluation, testing, and treatment
  • Assistance with sputum collection for submission to the Wisconsin State Lab of Hygiene (WSLH) for diagnosis and monitoring treatment response
  • Provision of antituberculosis medications; there is no charge for TB-related medications through the Wisconsin TB Dispensary for uninsured or underinsured persons
  • Management of care, from diagnosis to cure
  • Provision of directly observed therapy (DOT) for all clients with TB disease and clients with LTBI on a case-by-case basis
  • Education on TB for patients and families
  • Monitoring of medication side-effects and adherence
  • Management of clients with complex social and economic needs affecting adherence to the TB treatment plan

In addition, the public health department provides the following services for individuals with TB disease:

  • Facilitation of respiratory isolation for persons with infectious TB
  • Identification and monitoring of contacts, including TB testing (IGRA or TST) when necessary.

Active Tuberculosis (TB) Disease and Latent TB Infection (LTBI) Comparison Chart
CategoryLatent TB Infection (LTBI)Active Tuberculosis (TB) Disease
Bacterial LoadThe patient has a small amount of TB bacteria in their body that are alive, but inactive.The patient has a large amount of active TB bacteria in their body.
InfectiousnessThe patient cannot spread TB bacteria to others and does not require respiratory isolation.The patient may spread TB bacteria to others and may require respiratory isolation.
SymptomsThe patient does not feel sick, but may become sick if the bacteria become active in their body.The patient may feel sick and may have symptoms such as a cough, fever, and/or weight loss.
Test Results: Interferon gamma release assay (IGRA) or tuberculin skin test (TST)The patient usually has a positive IGRA or TST result indicating TB infection.The patient usually has a positive IGRA or TST result indicating TB infection.
Chest radiographyThe patient usually has a normal radiograph.The patient may have a radiograph that is abnormal.
MicrobiologyThe patient will have negative sputum smears and cultures.The patient may have positive sputum smear results and cultures in which M. tuberculosis is isolated.
TreatmentThe patient should be encouraged to take treatment for LTBI to prevent TB disease.The patient needs treatment for TB disease.

Persons being evaluated for TB disease or LTBI should be screened for risks of infection, risks for disease progression, and symptoms. 

People who had close contact with someone with infectious TB or who were born, lived, or traveled extensively in a TB endemic country are at highest risk for TB.

Wisconsin TB Risk Assessment Questionnaire and Symptom Evaluation form, F-02314b (PDF)

TB disease

Persons should be screened and tested for TB disease if they have a persistent cough lasting three or more weeks and one or more of the following symptoms:

  • Unexplained weight loss
  • Fever
  • Night sweats
  • Fatigue
  • Hemoptysis
  • Laboratory tests or radiographic evidence consistent with TB
Latent TB infection

Persons with latent TB infection will not have any of the symptoms listed above and instead should be tested based on:

  • Epidemiologic risk of infection
  • Regulatory requirements of their occupation
  • Risk of progression to TB disease

Testing for TB infection usually means performing a skin test (TST) or IGRA (QuantiFERON® or T.Spot.®TB) blood test. IGRAs are preferred, especially for persons born outside the U.S. due to higher test specificity. Testing for LTBI in low risk individuals is not recommended because of increased likelihood of false positive results (see CDC 2016 Testing and Diagnosis guidelines). Before being diagnosed with LTBI, low-risk individuals who test positive by either IGRA or TST should have a second, confirmatory test.

Persons who are suspected of having active TB disease may have false negative IGRA or TST results. Additional methods of evaluation are needed to diagnose TB disease (see radiography and microbiological test sections below).

Any testing should be considered together with the person’s risk of infection. Risk for TB is very low in Wisconsin. The majority of persons with TB acquire the infection outside of Wisconsin. Clinicians should be aware of populations at risk for TB in their area to help guide testing and evaluation decisions. Contact the Wisconsin TB Program for additional information.

All patients with a newly confirmed positive IGRA or TST test should be evaluated with a chest radiograph (chest x-ray or chest CT). Chest x-rays (CXRs) are reasonably sensitive for pulmonary TB disease, and the vast majority of patients with newly positive TB tests can be cleared (active TB disease ruled out) based on a normal CXR and negative symptom evaluation alone. A single posterior-anterior (PA) view is usually adequate to rule out active TB disease in asymptomatic adults without TB risk factors.

Adding a lateral view to the PA CXR may improve sensitivity for detecting active TB in immune-compromised persons, who are more likely to have atypical radiographic presentations of active TB (Meyer 2003; Eisenberg 2009). Additional imaging to rule out active TB disease may be indicated based on clinical assessment or discussion with the radiologist. A lateral view is also recommended for children under 10 years of age.

Note that CXRs are likely to be normal in patients with extrapulmonary TB disease, so the absence of lung disease on CXR does not indicate absence of infectiousness. Oropharyngeal and laryngeal TB are highly infectious, but disease cannot be detected by plain radiograph.

Persons who are suspected to have pulmonary TB disease, either because of abnormal chest radiograph or TB symptom evaluation, should have sputum specimens collected and sent to the laboratory for smear, culture, and molecular testing (PCR), if indicated. A series of three specimens, at least eight hours apart with at least one being an early morning specimen, are collected to diagnose pulmonary TB, determine infectiousness and release from airborne isolation, and monitor response to treatment. Persons unable to spontaneously produce sputum, P-02380 (PDF) may benefit from nebulized induction, P-02381. (PDF) Persons for whom bronchoscopy is performed should attempt to give sputum samples after the procedure, given the increased sensitivity of post-bronchoscopy specimens (CDC 2017 Diagnostic Guidelines). (PDF)

Persons who are suspected to have extrapulmonary TB disease should have other appropriate specimen samples, such as lymph node aspirates, collected and sent to the laboratory for smear and culture. All patients with confirmed extrapulmonary TB should have sputum specimens submitted for smear and culture to help rule out pulmonary TB disease.

All persons with suspected active TB disease, both pulmonary and extrapulmonary, should be reported to the patient's local health department. Clinicians are encouraged to send specimens to the Wisconsin State Laboratory of Hygiene (WSLH) where rapid full-service mycobacteriology and fee exempt TB PCR testing are available. Local health departments may be able to assist with collecting sputum from high-risk persons with suspected TB. Specimen collection kits and fee-exempt specimen transport are available by calling the WSLH customer service line at 1-800-862-1013.

Both LTBI and active TB disease are treatable. Many regimens are available, depending on the person's medical history and the drug (antibiotic) susceptibility patterns, if known.

Latent TB infection

See below or view common LTBI treatment regimens, P-01181 (PDF) See the Wisconsin TB Program publication, P-01181 (PDF) and the CDC website for more detailed information.

Isoniazid (INH) and Rifapentine (RPT)3 monthsOnce weekly, usually by directly observed therapy (DOT)
Rifampin (RIF)4 monthsDaily
Isoniazid (INH)6-9 monthsDaily

Active TB disease

Shown below are the preferred regimens for drug-susceptible, uncomplicated pulmonary TB disease in Wisconsin. Treatment completion is measured by number of doses completed by directly observed therapy (DOT). See current CDC treatment guidelines for more detailed information.

Intensive PhaseContinuation PhaseComments

Isoniazid (INH), Rifampin (Rif),
​Pyrazinamide (PZA), and Ethambutol (E):

7 doses/week for 56 doses (8 weeks), or

7 doses/week for 14 doses (2 weeks) then 5 doses/week for 30 doses (6 weeks)

Isoniazid (INH), Rifampin (Rif):

5-7 doses/week for 18-31 weeks (130-182 doses)

Preferred regimen for patients with new pulmonary TB.

Isoniazid (INH), Rifampin (Rif),
Pyrazinamide (PZA), and Ethambutol (E):

7 doses/week for 56 doses (8 weeks), or

7 doses/week for 14 doses (2 weeks) then 5 doses/week for 30 doses (6 weeks)

Isoniazid (INH), Rifampin (Rif)

3 doses/week for 18-31 weeks (94-110 doses)

Preferred alternative regimen for situations in which frequent DOT is difficult to achieve


Questions about TB? Contact Us!

Phone: 608-261-6319 ǀ Fax: 608-266-0049

Last revised December 6, 2023