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Ajay writes:

I was administered the Mantoux / PPD tuberculosis skin test on the same day that I received the Measles / Mumps / Rubella (MMR) vaccine. I tested positive for tuberculosis. Is it true that the results may be wrong because of the MMR vaccine?

Dear Ajay:

Let me first address the occurrences of erroneous results in tuberculosis (TB) testing.

There are two types of erroneous results:

False-negative

False-positive

False-Negative Results in TB Testing

There are times when a person may test negative for tuberculosis, when in fact, they do have tuberculosis (TB Disease/Active TB) or they have been exposed to tuberculosis (TB Infection/Latent TB). This is referred to as a false-negative result.

A false-negative TB test result occurs when a person's immune system is weakened by a disease, such as HIV, cancer or even tuberculosis itself, because the body may not be able to react to the TB test. Read more...

False-Positive Results in TB Testing

There are also times when a person may test positive for a TB test, when in fact, they do NOT have tuberculosis, nor have they been exposed to tuberculosis. This is referred to as a false-positive result.

False-positive reactions to the tuberculosis skin test typically occur because of an infection with nontuberculous mycobacteria or previous administration of the BCG vaccination. Read more...

The MMR Vaccine and TB Testing

Theoretically, the Measles / Mumps / Rubella (MMR) vaccine can suppress a reaction to the Mantoux / PPD tuberculosis skin test (i.e. the MMR vaccine can cause a false-negative tuberculosis skin test result). It is for this reason healthcare professionals will do one of the following when both are needed:

Same Day Administration. The preferred method is to administer the Mantoux / PPD TB test and the MMR vaccination during the same visit. This will eliminate any interference in the reading of the Mantoux / PPD TB test at the 48 to 72 hours read time.

Delay TB Testing. If you have already received the MMR vaccine, you should wait at least 4 weeks before receiving the Mantoux / PPD TB test. This should only be done in cases where the Mantoux / PPD TB test is NOT needed immediately. This is not the preferred method because it delays TB testing.

Delay MMR Vaccination. The Mantoux / PPD TB test can be administered and read before the MMR vaccination. However, this should only be done in cases where the MMR vaccination is NOT needed immediately. This is not the preferred method because it delays the administration of the MMR vaccination.

Ajay, you received the preferred method - same day administration of the Mantoux / PPD TB test and MMR vaccination. Since the MMR vaccine is only known to cause a false-negative TB test result, your positive TB test result is highly unlikely to be due to the MMR vaccine.

Be sure to talk to your doctor about a follow-up chest x-ray and/or sputum culture to verify or dispel a tuberculosis diagnosis.

Chest X-Ray | Sputum Culture

_{Source: National Guideline Clearinghouse
Updated: 02/26/06}