Answer 1 Exposure

Infection does not necessarily follow exposure. Only a small percentage of people exposed develop infection.











Answer 2

Class 2










Answer 3 INH Chemoprophylaxis

The indications for INH chemoprophylaxis are:

  1. Home contact
  2. Recent conversion positive skin test
  3. Under the age of 35
  4. T cell defects (on steroids, lymphoma, immunosuppression, etc.)
  5. Unstable diabetes

Two considerations are:

  1. What is the possibility of developing active disease
  2. What is the risk of developing INH liver toxicity

If you look at all new patients with active tuberculosis, you will see that 95% of the cases are coming from patients who had positive skin tests previously. The risk for active tuberculosis in people with negative skin tests is so small, it is not worth the effort. That excludes about 200 million people in the United States. There are approximately 10 million people with positive skin tests. Let us next consider the statistical probability of developing tuberculosis:

  1. Negative skin test
  2. Home contact
  3. Recent conversion
  4. Under the age of 35 with positive PPD
  5. T cell defect
  6. Over the age of 35 with positive PPD

The risk of developing INH liver toxicity is greatest in:

  1. People under the age of 35
  2. People over the age of 35















Answer 4 Exposure

Yes. Retest again in three months. If still negative, stop the INH.











Answer 5 Exposure

Being a household contact, he will be a candidate to receive prophylaxis, irrespective of skin test results.

Our concern is, what is the risk of developing INH hepatitis? With increasing age, the risk of developing hepatitis with INH increases. His skin test results may suggest that he is not infected or that there has not been enough time for him to develop an immunological reaction.

Multiple myeloma is a B cell disease. As such, patients have problems with immunoglobulins. Only patients with T cell problems have a higher risk of developing tuberculosis.

These are the issues we have to consider before deciding on chemoprophylaxis. We have two options:

  1. Start him on INH and repeat the PPD in three months. If positive, INH should be continued for one year. If negative, discontinue INH.
  2. Wait for three months and repeat the PPD. If positive, immediately start INH prophylaxis. If negative, we need not consider him for prophylaxis.

I follow the second option.











Answer 6 Exposure

She has a positive skin test and is a home contact. However, she had been positive five years ago. Once you've had an infection, you're protected from exogenous infection. If she gets the disease, it will be from reactivation or endogenous focus. She is not a candidate for prophylaxis.