I Have a Child With a Positive Tuberculin Test

Does the child have risk factors for tuberculosis?
The most common risk factors are birth in a country where tuberculosis is common, living with a foreign born adult, or travel to a country at high risk for tuberculosis. 15 mm of induration is considered a positive skin test in a healthy child over 4 years with no risk factors for Tb.

Is the child ill with symptoms of tuberculosis or is the child immune compromised?
If the answer to either question is yes, then 5 mm of induration is considered a positive test and evaluation for active tuberculosis including careful history, physical examination and chest radiographs should be done. Tuberculosis is a slowly progressive disease but evaluation should not be delayed in symptomatic children.

What are the symptoms of tuberculosis in children?
Most children with active Tb are not acutely or severely ill. Fever, persistent cough, weight loss (failure to thrive), pneumonia not improving on antibiotics are some of the most common presentations.

Was the child recently exposed to a family, household or other close contact with known or suspected tuberculosis?
If the answer is yes 5mm of induration is considered a positive test and the child needs further evaluation.

Was the tuberculin test properly placed and read?
A Mantoux test consists of 5TU (0.1ml) of PPD injected intra-dermally, creating a wheal without bleeding.  Induration is measured 48-72 hours later in mm using a ball point pen and ruler perpendicular to the long axis of the arm. Improperly placed Mantoux tests are not interpretable and should be repeated. Tine or other multiple puncture tests are not recommended.

Is the physical examination abnormal? 
Many physical findings are described in tuberculosis. However many children with active tuberculosis have a normal physical examination. An abnormality on examination usually indicates more advanced or severe disease.

Do all children with a positive tuberculin test need a chest xray?
Yes. PA and lateral chest radiographs should be examined by someone familiar with tuberculosis in children. We ignore any prior history of receiving BCG in the decision to place and interpret a tuberculin test and in the decision to obtain a chest xray. A child with a positive tuberculin test, no symptoms of tuberculosis with a normal chest xray is considered to have latent tuberculosis infection. (LTBI).

How should LTBI be treated?
Isoniazid 10 -15mg/kg/day (maximum 300mg) once daily for 9 months is standard. 100 and 300 mg scored tablets are used as INH suspension causes diarrhea. Routine liver function or other laboratory tests are not needed except in teens (ETOH should be avoided), children with liver disease or taking hepato-toxic medicines. Toxicity is monitored clinically. LFTs are measured in children who develop anorexia, vomiting, or abdominal pain on INH. Children treated for LTBI do not need follow-up chest xrays nor should skin tests be repeated.

The parents believe the BCG vaccine caused the positive skin? 
BCG is given as a routine neonatal or childhood vaccine throughout much of the developing world. BCG is used in countries where tuberculosis is common and exposure of young children to tuberculosis is frequent. BCG reduces the incidence of disseminated Tb but does not prevent infection. Although BCG may cause a positive skin test, the reactions are usually small, less than 10mm and decrease with time since the BCG. It is not possible in an individual child to prove that a positive skin test is due to BCG, so usually for the safety of the child we ignore the previous BCG history.

Who can I call for help?
Cases of active tuberculosis are reportable and are given directly observed therapy (DOT). Denver Metro Tuberculosis Clinic (303-436-7286), the county health department or the Tuberculosis Control Program of the Colorado Department of Public Health and Environment (303-692-2638) should be notified of active cases and can assist with evaluation and treatment. Dr. John Ogle (303-436-6690) provides the Pediatric staffing for Denver Metro Tb Clinic and can also help with questions.