County of Marin Health and Human Services

Tuberculosis: Health Care Providers

The Centers for Communicable Disease and Prevention Control (CDC) has released a guide (2013) for primary care providers who care for individuals at risk for infection with Mycobacterium tuberculosis. Latent tuberculosis infection (LTBI) is the presence of Mycobacterium tuberculosis in the body without signs and symptoms, or radiographic or bacteriologic evidence of tuberculosis (TB) disease. 

Never begin treatment for LTBI until active TB disease is ruled out. A suspected case of active TB disease is required by law to be reported within one working day to Marin County TB Control by telephone at 415 473 4163, or by fax at 415 473 6002.

Health care providers must complete a confidential online report for all suspect and active tuberculosis cases among Marin County residents. Please do not wait for laboratory confirmation before reporting.

Health care facilities must complete the Tuberculosis Discharge Treatment Plan (updated July 2018) prior to discharge and fax to the County of Marin TB Control Program at 415 473 6002.  

LTBI Guidelines

CDPH CTCA Latent Tuberculosis Infection Guidance for Preventing TB in California, 2018 Revision

Process for Evaluating Latent TB Infection and Active TB

Who to Test: Using the Risk Assessment

Because approximately 80% of tuberculosis is due to the reactivation of LTBI, routine assessment of TB risk followed by testing and treatment are crucial to preventing However, routine testing of low risk populations is not recommended and may result in unnecessary evaluations and treatment because of falsely positive test results. CDPH and CTCA created the following TB Risk Assessment tools to assist clinical providers in determining whether or not to test for LTBI.

Selecting a Test for Latent TB Infection (LTBI)

For most people with an indication for testing based on a risk assessment, interferon gamma release assays (IGRAs), such as the Q uantiferon or T-Spot TB, are preferred over the tuberculin skin test (TST). IGRA is especially helpful in persons who have previously been BCG-vaccinated (most persons born outside the U .S.).

BCG Vaccination & TB Testing

BCG, or bacille Calmette-Guérin, is a vaccine for tuberculosis (TB) disease. Many foreign-born persons have been BCG-vaccinated. The TST and TB blood tests to detect TB infection are not contraindicated for persons who have been vaccinated with BCG. Blood tests to detect TB infection, unlike the TST, are not affected by prior BCG vaccination and are less likely to give a falsepositive result.

Map on current & past BCG policies worldwide

Interpreting TB Skin Test (TST) Results

Online training on administration of the TST using the Mantoux method.  

IGRA Clinical Guidelines

For many years the Mantoux tuberculin skin test (TST) has been the basic screening test for detecting latent tuberculosis (TB) infection (LTBI). In 2005, the Food and Drug Administration (FDA) approved an in vitro laboratory diagnostic test, QuantiFERON ®- TB Gold (QFT-G) to aid in diagnosing Mycobacterium tuberculosis infection. In 2010, the CDC published updated guidelines for using IGRAs to detect Mycobacterium tuberculosis infection (MMWR; 59 [No. RR-5]: 1-25).  

Evaluating Patients with a Positive TB Test

All patients with a positive test for LTBI should undergo a baseline evaluation including:

  • Symptom review
  • Chest radiograph taken within 6 months if normal; or within 3 months if there is known close contact with a person with infectious TB, immunosuppression, or a previously abnormal CXR consistent with potentially active TB disease. A current CXR should be obtained for patients with new symptoms.
  • Medical history, including HIV status, history of liver disease, alcohol use, other medicines including those that are potentially hepatotoxic or have drug-drug interactions with rifamycins or isoniazid

Persons > 5 years of age should have a posterior-anterior view radiograph. Children under 5 years of age should have both posterior-anterior and lateral views.

Choosing a Treatment for Latent TB Infection (LTBI)

If the known source of TB Infection has drug-resistant TB, consultation with Marin County TB Control is advised.

Treatment Regimens

Sample Script to Explain LTBI Treatment

There are several treatment regimens available for the treatment of latent TB infection (LTBI). Providers should choose the appropriate regimen based on the following:

  • Drug-susceptibility results of the presumed source case (if known)
  • Coexisting medical illness
  • Potential for drug-drug interactions

For persons who are at especially high risk for TB disease and are either suspected of nonadherence or are given an intermittent dosing regimen, directly observed therapy (DOT) for LTBI should be considered.  Please contact the Marin County Tuberculosis Control program if you need assistance with DOT.

12-dose Isoniazid (INH) + Rifapentine Regimen for Latent TB Infection (LTBI) Treatment
Rifampin for Latent TB Infection (LTBI) Treatment
Isoniazid (INH) for Latent TB Infection (LTBI) Treatment

Monitoring a Patient on LTBI treatment

To ensure safe and efficacious treatment for LTBI, the health care provider should periodically assess the patient’s progress. This evaluation involves clinical monitoring and laboratory testing, as well as patient education.

  • Patients should visit the health care provider who is managing their treatment on a monthly basis to be assessed for the following:
    • Signs of hepatitis
    • Adherence to medication regimen
    • Symptoms of possible adverse drug reactions or interactions

Patients being treated for LTBI who experience possible adverse reactions should be advised to stop medication and consult their health care provider immediately.

LTBI Treatment Completion

Providers should:

  • Inform patients that there is a small risk that they could develop active disease in the future (and this risk has been greatly reduced due to LTBI treatment)
  • Re-educate patients about the signs and symptoms of TB disease
  • Advise patients to contact the medical provider if he or she develops any of these signs or symptoms
  • Remind patients that their TB test will likely always be positive despite completing treatment and to avoid additional TB testing by showing documentation of completing treatment.

Completion Card/Letter (Samples)