TB Tests and BCG: Your Questions Answered

Q: TB Tests and BCG: Your Questions Answered

Albert： Hello, I will briefly answer your questions as follows： 1. <br>A positive tuberculin skin test indicates that you have been infected with the tuberculosis bacteria (approximately one-third of the global population has been infected), but you are not currently ill (no pulm

TB Test and BCG Vaccine

I moved to the United States at the age of four.
In Taiwan, I received the BCG vaccine, and in 1996, I had a TB test that was negative.
During a school health check this year, the doctor asked me to return in 48 hours to check the results, but due to circumstances, I did not go back until six days later, at which point the induration had increased to 15 mm.
The doctor indicated that this was positive and requested a chest X-ray, which returned negative.
Nevertheless, the health center still required me to take Isoniazid 300 mg for nine months.
After taking it for one month, my blood test showed elevated alkaline phosphatase levels at 134 U/L.
I have two questions: 1.
Do I really have tuberculosis? 2.
Should I continue taking Isoniazid, or should I stop? I am concerned about its effects on my liver.
Thank you for taking the time to address my concerns.
Have a wonderful day.

Albert, 10~19 year old female. Ask Date: 2005/01/12

Dr. Yang Wenda reply Pulmonology

Albert: Hello, I will briefly answer your questions as follows: 1.
A positive tuberculin skin test indicates that you have been infected with the tuberculosis bacteria (approximately one-third of the global population has been infected), but you are not currently ill (no pulmonary tuberculosis, and chest X-ray is normal).
2.
If you have a latent tuberculosis infection, you may consider using INH for 9 months to treat it, as studies show this reduces the risk of developing active disease later.
3.
Less than 2% of individuals may experience drug-induced hepatitis, which is more common in the elderly and those with a history of hepatitis.
It is recommended that you continue treatment unless you experience abnormal liver function (which may present with symptoms such as loss of appetite and nausea).
Wishing you well!

Reply Date: 2005/01/12

More Info

Understanding tuberculosis (TB) tests and the implications of BCG vaccination can be quite complex, especially when considering your specific situation. Let's break down your concerns regarding the TB test results, the BCG vaccination, and the use of Isoniazid.

1. Do You Really Have Tuberculosis?
Your history indicates that you received the BCG vaccine in Taiwan, which is commonly administered to protect against tuberculosis. The BCG vaccine can cause a positive reaction in TB skin tests (TST) or interferon-gamma release assays (IGRAs), as it stimulates an immune response similar to that of an actual TB infection.
In your case, the initial TB test resulted in a 15mm induration after 6 days, which is considered positive. However, the subsequent chest X-ray was negative, indicating no active pulmonary TB disease. This scenario suggests that while you may have been exposed to TB or have a latent TB infection (LTBI), you do not have active TB disease at this time.

2. Should You Continue Taking Isoniazid?
Isoniazid is a first-line medication used to treat latent TB infection to prevent the development of active TB disease. Given that your TB skin test was positive and your chest X-ray was negative, your healthcare provider likely recommended Isoniazid as a preventive measure.
However, you mentioned experiencing elevated alkaline phosphatase levels after one month of treatment. Alkaline phosphatase can be elevated for various reasons, including liver issues, bone disorders, or other metabolic conditions. Since Isoniazid can potentially cause liver toxicity, it is crucial to monitor liver function during treatment.
Given your concerns about liver health, it is essential to discuss your elevated alkaline phosphatase levels with your healthcare provider. They may recommend further liver function tests or consider adjusting your treatment plan based on your overall health and any symptoms you may be experiencing.

Conclusion and Recommendations
1. Monitoring and Follow-Up: Continue to follow up with your healthcare provider regarding your TB status and the effects of Isoniazid. Regular monitoring of liver function tests is advisable while on this medication.

2. Understanding TB Infection: It is important to differentiate between latent TB infection and active TB disease. Since your chest X-ray is negative, it is likely that you have latent TB, which is not contagious but requires treatment to prevent future complications.

3. Lifestyle Considerations: Maintain a healthy lifestyle, including a balanced diet and regular exercise, to support your liver health. Avoid alcohol and consult your doctor before taking any new medications or supplements.

4. Communication with Healthcare Providers: Keep an open line of communication with your healthcare providers. If you experience any new symptoms or have concerns about your treatment, do not hesitate to reach out for guidance.

In summary, while you may not have active TB, the positive skin test indicates a need for preventive treatment. Continue your medication as advised, but ensure that your liver function is monitored closely. Your health and safety are paramount, and your healthcare team is there to support you through this process.

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