Those with a normal chest x-ray result who are HIV-negative are unlikely to have pulmonary TB, and sputum collection is unnecessary. For those with suspicious chest x-ray films and for those who are HIV positive with TB symptoms, sputum samples are needed for microscopic evaluation and culture (3 samples, preferably on 3 consecutive days).
Acid-fast organisms seen under the microscope may be Mycobacterium tuberculosis or mycobacteria other than tuberculosis (commonly referred to as MOTT), and the final determination must await culture confirmation, which now takes about 4 weeks. Preliminary confirmation using polymerase chain reaction can be accomplished in a few days. Treatment for active TB should be initiated, however, and the suspicion reported to the local health department as soon as TB is suspected.
Treating latent and active disease
Latent tuberculosis. Treatment for latent TB (positive TB skin test result, negative chest x-ray film, HIV-negative) should not be initiated until active TB is ruled out. This may require waiting 3 to 4 weeks for sputum culture results.
Contrary to common belief, there is no age cutoff for initiation of treatment for latent TB. Treatment requires 6 to 9 months of isoniazid or 4 months of rifampin. A shorter course with pyrazinamide and rifampin is also possible, although questions about the safety of this regimen have been raised. Patient compliance for the duration of therapy is difficult to achieve; but if accomplished, the risk of active disease decreases from 10% to less than 1%. At highest risk of developing active disease are children, and those who are HIV-positive, recently infected with TB, or whose chest films indicate old disease.
Since isoniazid is hepatotoxic, patients should be asked about symptoms of liver inflammation (abdominal pain, decline in appetite, dark urine, light-colored stools), and liver function tests should be ordered if symptoms are present. Routine monthly testing of liver function tests is not necessary and is recommended only for those who have chronic liver disease, an alcohol abuse disorder, or are pregnant.
Active tuberculosis. Always initiate treatment with at least 3 drugs (isoniazid, rifampin, and pyrazinamide). Ethambutol should be added to the regimen if patients are current or former residents of an area where resistance to isoniazid is more than 5%. If the organism proves sensitive to isoniazid and rifampin, ethambutol can be discontinued. Pyrazinamide should be continued for a full 2 months, and isoniazid and rifampin for a full 6 months. A variety of protocols for dosing and administration frequency are available to enhance convenience and patient compliance. Drug regimens may have to be adjusted based on culture results and success of therapy.
The standard of care for active TB is directly observed therapy. This means watching the patient swallow the pills. Although such care is labor intensive and implies a lack of trust in the patient, with its implementation, the successful completion of therapy rises from 50% to close to 100%. Widespread use of directly observed therapy since the late 1980s has resulted in a marked reduction of TB rates and rates of bacterial resistance.
To prevent bacterial resistance to drugs, treatment for active disease must be administered according to guidelines and be completed. One cardinal rule in the prevention of bacterial resistance is never to add just 1 drug to a failing regimen.
Any deviation from standard therapy because of bacterial resistance, patient nonadherence, or adverse drug effects is reason to consult the local public health department or state public health department TB program.
Working with the public health department
Three complementary activities are needed to control TB in the community:
- Finding and treating those with active TB
- Investigating close contacts of persons with active disease and offering them treatment of latent TB
- Screening persons at high risk, to find and treat latent TB.
The detection and management of tuberculosis offers an excellent opportunity for family physicians and health departments to work collaboratively to improve the community’s health.
Family physicians can make several contributions to reducing TB’s impact on the community:
- Screen appropriately
- Correctly apply and interpret TB skin tests
- Accurately make the diagnosis of latent and active TB
- Treat active TB according to recommended guidelines
- Encourage treatment of latent TB among those at highest risk of activation
- Promptly report to the local health department those suspected of having TB
- Collaborate with the public health department to reduce the spread of disease.
Local or state public health departments assist in several ways:
- Communicate with and investigating family and other close contacts of those with active, contagious TB, to find anyone with latent or active TB
- Offer consultation on how to diagnose and treat latent and active TB
- Assist with directly observed therapy
- Use public health authority to isolate and quarantine patients who are infectious and pose a risk to the community through non-adherence to treatment and infection control guidelines.