TB Disease Case Definitions

Active TB disease

Tuberculosis is a reportable infectious disease, as stipulated in Minnesota Rules Governing Communicable Diseases. Confirmed or suspected cases of TB disease must be reported to MDH within 1 working day of identification. Both pulmonary and extrapulmonary forms of TB disease are reportable.

To report a confirmed or suspected case of TB disease, call the TB Prevention and Control Program at 651-201-5414 or 1-877-676-5414, or fax 1-800-296-0993. To ensure timely public health follow-up measures, please report all TB cases by telephone or fax and not by mail.

The physician, infection preventionist, laboratory, or other reporting agent should report to MDH all TB cases that meet either the laboratory or clinical case definition, as follows:

TB Laboratory Case Definition

• Isolation of M. tuberculosis complex from a clinical specimen,*
  OR
• Demonstration of M. tuberculosis complex from a clinical specimen by nucleic acid amplification test,**
  OR
• Demonstration of acid-fast bacilli in a clinical specimen when a culture has not been or cannot be obtained or is falsely negative or contaminated.

TB Clinical Case Definition

A case that meets all of the following criteria:

• A positive tuberculin skin test result or positive interferon gamma release assay for M. tuberculosis
• Other signs and symptoms compatible with tuberculosis (TB) (e.g., abnormal chest radiograph, abnormal chest computerized tomography scan or other chest imaging study, or clinical evidence of current disease)
• Treatment with two or more anti-TB medications
• A completed diagnostic evaluation

* Use of rapid identification techniques for M. tuberculosis (e.g., DNA probes and mycolic acid high-pressure liquid chromatography performed on a culture from a clinical specimen) are acceptable under this criterion.

** Nucleic acid amplification (NAA) tests must be accompanied by culture for mycobacteria species for clinical purposes because a culture isolate of M. tuberculosis complex is required for complete drug susceptibility testing and also genotyping. However, for surveillance purposes, results obtained from NAA test approved by the Food and Drug Administration (FDA) and used according to the approved product labeling on the package insert, or a test produced and validated in accordance with applicable FDA and Clinical Laboratory Improvement Amendments (CLIA) regulations are acceptable.

TB Suspects

In addition, suspected cases of TB disease that meet the following criteria should be reported immediately to MDH, prior to final confirmation by the laboratory or clinical case definition:

(a) a positive microscopic smear result for acid-fast bacilli (AFB) from a respiratory or extra-pulmonary specimen AND clinical, radiographic, laboratory, or epidemiologic evidence consistent with active TB disease,
OR
(b) clinical, radiographic, laboratory, or epidemiologic evidence consistent with active TB disease AND clinical specimens for bacteriologic testing are not available or bacteriologic test results are negative for M. tuberculosis
OR
(c) multi-drug therapy for treatment of TB disease has been prescribed.

Latent TB infection

Latent TB infection is not a reportable condition in Minnesota.