Diagnosis & Treatment of Latent TB Infection
Treatment of Latent TB Infection (LTBI) is essential to controlling and eliminating TB in the USA. Treatment of LTBI substantially reduces the risk that TB infection will develop into disease. Click here to read more about conditions that increase the risk of progression to TB Disease.
Testing for TB Infection
The test we use is called the Mantoux test. A small quantity (0.1 ml) of a solution containing a small but precise amount of protein derived from the TB bacteria is injected under the skin. You cannot get TB from the solution. Between 48 - 72 hours a trained person inspects the site for a firm lump (induration) just under the skin and carefully measures it (in mm).
To determine a positive skin test depends on your individual risk factors and the size of the reaction as explained below.
A reaction of 5mm or more is positive for:
- HIV positive persons
- Recent contact to a known Active TB case
- Chest X-Ray with fibrotic changes consistent with old TB
- Persons with organ transplants and other immunosuppressing conditions or treatments (ie. high dose prednisone)
A reaction of 10mm or more is positive for:
- Immigrants from high-prevalence countries (link: TB Worldwide)
- Injecting drug Users
- Residents and employees of high-risk congregate settings (ie. jails/prisons, nursing homes, homeless shelters, hospitals, and other health care facilities)
- Persons with clinical conditions that make them high-risk
- Children under 4 years of age, or children and adolescents exposed to adults in high-risk categories
A reaction of 15mm or more is positive if:
- No known risk factors.
Treatment of Latent TB Infection
There are several medicines (antibiotics) that are recommended to kill the Latent TB Infection before it has a chance to become active. The amount of medicines to treat LTBI is much less than those for Active TB disease.
The best treatment option is Isoniazid (INH). The normal dose for adults is 1 pill (300mg) Daily for nine months (270 doses taken within 12 months).
Side effects are uncommon, especially for those under the age of 35, and most don't notice any effect whatsoever. However, as with any medicine, a small number of people experience adverse reactions. We monitor our clients closely by asking focused questions and, if any problems are noted, getting the appropriate tests done with medical follow-up.
If a person is at risk for developing active TB and cannot tolerate INH, or if the person contracted the infection from a strain of TB known to be INH-resistant, then other medicines are available to use instead.
Side effects associated with Isoniazid
Peripheral neuropathy - a numbness or tingling most often felt in the fingertips. In most cases, this is overcome by taking Vitamin B6 while on INH.
Liver Inflammation - a much rarer effect (1-2%) primarily affecting those with a history of alcohol/drug abuse, or chronic liver infections (Hepatitis B or C). Signs of this include: extreme fatigue (tiredness), muscle weakness, loss of appetite, coffee/tea-colored urine, pale stools, yellowing of whites of eyes and skin. The liver is a strong organ and has the ability to regenerate very quickly. There are blood tests that can give us a very accurate picture of how the medicine is affecting it.
Treat Latent TB Infection!