Our international adoption practice includes children from parts of the world where tuberculosis is much more prevalent than in the US, and kids from especially high-risk backgrounds for TB, like institutional care. Research on international adoptees reveals that about 1 in 5 children from these backgrounds will have positive skin tests for tuberculosis (called PPDs) on arrival, or at the retest 6 months later. This brief article gives some background on TB, and rationale for testing and treatment.
Tuberculosis is an infection with Mycobacterium Tuberculosis (TB). While the most common site of infection is the lungs, it can affect many parts of the body. It is an atypical infection and most of the time, infection does not cause any symptoms initially. When an individual is infected by TB but has no symptoms, physical findings, or chest x-ray abnormalities, then they have Latent Tuberculosis Infection (LTBI, or "inactive TB"). Patients with LTBI are not ill appearing, have no symptoms, and are not contagious (i.e. they cannot spread the infection to others).
The reason it is very important to treat LTBI is that if not treated, there is a 5-10% lifetime risk of developing Active Tuberculosis, which is a life threatening illness. Some people have an even higher risk of progression to active disease and these include: infants, adolescents, patients who were infected within the previous two years, patients with compromised immune systems (like HIV), patients with chronic illnesses such as diabetes or kidney disease. LTBI is treated with a medication called isoniazid (INH). It is given once daily for nine months. The liquid preparation is hard to tolerate and often causes bad diarrhea so we generally prescribe a tablet that can be crushed.
Tuberculosis is typically diagnosed using a skin test or a PPD. This should be tested at arrival and again 6 months later, regardless of whether they had BCG (TB immunization) previously or not. A positive PPD reading depends on the risk factors for a particular patient and is sometimes a bit difficult to read, so it is important to have it read by someone who does this often. There are some newer blood tests for diagnosing Tuberculosis but these have not yet been approved in children, and it is unlikely that they will be approved in children under 5 years of age in the near future.
Frequently Asked Questions:
My child had a negative PPD previously, why is it positive now?
This can be for a number of reasons. Your child may have been newly exposed to TB since the previous test. Also the time from infection until the development of a positive PPD can be between 2 and 12 weeks. There are 10-15% of children with normal immune systems who have had culture proven disease with negative PPDs. Reasons for this include young age, poor nutrition, other viral infections, recent TB infection, and disseminated TB (an overwhelming full body form of the illness). Also kids with abnormal immune systems can have a falsely negative PPD. This is why we repeat a PPD on international adoptees and other children at high risk for TB six months later.
My child was given BCG (an immunization against TB), does this always cause a positive PPD?
No. BCG is given in many parts of the world to prevent TB and studies find it about 50% effective on average. It is more effective for preventing some more serious forms of TB in young children and that is why it is given. Typically it is given soon after birth. While it can cause a positive PPD, for those given BCG at less than 2 months of age, 40% have negative PPD by 1 yr of age and more than 95% have a negative PPD by 5 years of age. It is the young kids with the recent exposures that are at increased risk for developing active disease where it is the most unclear and those are the ones it is most important to treat. There are newer blood tests that may help us with this but not in kids under 5 years of age. Both the Centers for Disease Control and The American Academy of Pediatrics recommend ignoring the history of BCG injection when evaluating a PPD. However, a very recent, actively oozing BCG site is one situation where we may defer the PPD until the BCG site is more healed.
Are there any precautions I should take while my child is taking isoniazid?
Yes, there are, but isoniazid is actually very well tolerated in children. Adults over 35 years of age are more likely to have some liver inflammation, and are screened with blood tests, but this is not typically needed in children unless they have known liver issues. If your child develops unexplained abdominal pain, vomiting, or jaundice (a yellowing of the skin and eyes) then you should contact your doctor.
Your child may also experience an unpleasant reaction (headache, large pupils, neck stiffness, nausea, vomiting, diarrhea, sweating, itching, and chest pain) if they eat too much tyramine containing food, so those should be avoided or eaten in moderation. These foods include: aged cheeses, avocados, bananas, figs, raisins, beer, ale, caffeine (coffee, tea, colas), chocolate, meats prepared with tenderizer, liver, bologna, pepperoni, salami, sausage, meat extracts, caviar, dried or pickled fish, and tuna, red wine, sour cream and yogurt, soy products, and yeast. Some of those are childhood standbys (bananas & yogurt), some are not (beer). We've not heard many reports of this reaction, so mild-moderate consumption may be OK.
What is the best way to get my child to take the tablet?
A pill crusher will make the medicine into a powder for kids unable to swallow a pill. It is best to mix it in a small amount of something with a very strong flavor such as chocolate syrup or one of the syrups used for Italian sodas. We have a helpful article on "Taking Your Medicine". One clever family opened an Oreo cookie and mixed the powder with the icing in the middle of it, then replaced the top cookie. Their child really enjoyed the daily cookie for nine months!
Is it important to take this medicine every day?
Yes! In fact, some public health departments use "directly observed therapy" (having a nurse watch the patient take the meds) for TB. If a dose is missed, give the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
Isoniazid usually is taken once a day, on an empty stomach, 1 hour before or 2 hours after meals. However, if isoniazid causes an upset stomach, it may be taken with food. Find a time that works for your family, and set a recurring alarm/reminder.
Will my child need more testing after the isoniazid, or further PPDs?
Not unless they develop symptoms of tuberculosis. Their PPD will likely remain positive, but we will document that they had a clear chest x-ray and completed INH therapy. If TB is suspected later, or needs to be ruled out for job purposes, they can get a chest x-ray.