The tuberculosis commonly known as TB in the United States began to increase since 1986, mostly in the 26 to 44 year age group, About one third of all reported cases occur in blacks, 14% in Hispanics, 11% in Asians and Pacific Islanders and 2% occur in American Indians.
Tuberculin skin testing is the principal means of detecting TB infection in asymptomatic persons. The most accurate is the Monteux test, in which five units of tuberculin purified protein derivative (PPD) are injected intradermal to detect delayed hypersensitivity; the induration of 10 mm or more in diameter after 4872Z hours is generally considered a positive test. The frequency of false positive and false negative tuberculin skin tests depend on a number of factors. False positive results can be produced by improper technique (measuring redness rather than induration), reaction to PPD constituents or local inflammation. False negative reactions can be observed early in infection, in anergie individuals and those with severe illness. The later could be as a result of improper technique in handling the solution, administering the intradermal injection and interpreting the results.
A person with a known positive PPD does not need to have one repeated; if the test is repeated, there is a small risk of producing a ‘very strong reaction characterized by tender induration, axillary adenopathy, elevated temperature and local skin sloughing. Prophylaxis Recommendations: ‘The main purpose of preventive therapy is to prevent asymptomatic infection from progressing to clinical disease. This is also used to, prevent initial infection and to prevent recurrence of past disease.
High-risk Groups: In the United States, persons with any of the following six risk factors should be considered candidates for preventive therapy, regardless of age, if they have not been previously been treated:
- Persons with HIV infection or risk factors for it PPD more than 5mm.
2, Close contacts of persons with newly diagnosed infectious tuberculosis PPD more than 5mm,
Recent converters, as indicated by PPD (more than 10 mm increase within a two year period for those under 35 years old; more than 15 mm increase for those over 35 years of age.
- Persons with abnormal chest X-rays PPD more than 5 mm.
- Intravenous drug users with HIV negative status PPD more than 10 mm.
- Persons with certain medical conditions PPD more than 10 mm.
In the absence of any of the above risk factors, persons Less than 35 years of age in the following high incidence groups arc appropriate candidates for preventive therapy if their reaction to PPD is more than 10 mm; 1,Foreignborn persons from high prevalence countries. 2. Medically underserved low-income populations. 3. Residents of facilities for long term care ¢.g, nursing homes mental institutions and prisons.
Preventive Therapy: The usual preventive treatment is isoniazid (INH) with adult dose of 300 mg daily. The recommended duration is six to 12 months of continuous therapy. IN induced hepatitis occurs in about 1 to 2% of patients, the frequency increasing with age. The benefits of INH outweigh its side effects in persons at high risk for TB. Symptoms of liver damage or other toxic effects are anorexia, nausea, vomiting, fatigue or weakness, rash and elevated temperature. Monitoring by routine laboratory tests is not always helpful but they are mandatory.
This information provides a general overview on Tuberculosis Screening & Prophylaxis and may not apply in each individual case. Consult your physician to determine whether this information can be applied to your personal situation and to obtain additional information.
Article extracted from this publication >> July 16, 1993
