TB or not TB? That is congestion.

October 7, 2009 8:15 AM

Because my grandfather was in an iron lung, I've tested positive for TB since the day I was born. Nothing active, but I never got medication. Should I do something?

I was born in the US and am in excellent health. Still, I'm a little worried that one day my immune system will dip and I'll go active and start leaking germs without knowing it. Are preventative antibiotics worth it, or am I anxious about nothing?

I've done a lot of research studies as a "healthy normal," so have had every kind of imaging and then some: two bronchoscopies, all kinds of pulmonary function tests, a couple of PET scans, and more MRIs than I can remember. About five years ago I spent the night on oxygen in the ER for severe bronchitis and had chest x-rays; all clear on all fronts. The main reason I'm thinking about this now is a friend of mine is immunocompromised. I know latent infections can't spread, but still. All thoughts welcome!

posted by aquafortis to health & fitness (14 answers total)

Have you had a BCG vaccination? These are not common in the US, but I got mine in the UK when I was 10 or 11 and it has caused false positives on TB skin tests.
posted by IanMorr at 8:44 AM on October 7, 2009

Because my grandfather was in an iron lung, I've tested positive for TB since the day I was born.

Sorry, but I don't understand how that works. Could you elaborate?

Anyway, you're not worried about nothing, but you don't have a lot to worry about, either. Most people with a positive PPD but a clear chest X-ray do not ever develop an active infection, but some people do. Do you have a primary care doctor? Good question to raise with that person.
posted by molybdenumblue at 8:48 AM on October 7, 2009 [1 favorite]

I would think the best thing to do is to ask your doctor about this. Googling generally seems to suggest that if a blood test or chest X-ray says you don't have it, then your skin test is just a false positive.

(Also, can you explain the grandfather/iron lung/you testing positive for TB connection?)
posted by olinerd at 8:51 AM on October 7, 2009

No, you shouldn't seek treatment. For healthy individuals with latent TB the greatest chance of converting to active TB occurs in the year or two immediately post-exposure (I believe it's about 40%). After that the lifetime chance of developing active TB (for a healthy person) is quite low (~10%). I'm not a doctor.
posted by OmieWise at 9:02 AM on October 7, 2009

You don't have TB.

The TB skin test (alternatively known as Mantoux, Pirquet, etc.) tests for an immune response to tuberculin, a bacterial protein, not for the presence or absence of tubercle bacillus. People who have previously been given the Bacillus Calmette-Guerin TB immunization (used routinely in most countries outside of the USA) also test positive for antibodies against TB.

If your grandfather had TB, you were likely to have been exposed to Mycobacterium tuberculosis, the causative agent of TB, and therefore your body mounts an immune response whenever injected with anything it recognizes as a bacterium. That doesn't mean the bacteria are present in your system.
posted by halogen at 9:34 AM on October 7, 2009 [3 favorites]

While IANAD I have just had a lecture on TB. What OmieWise says is completely true; if you don't progress from primary TB to post-primary TB (post-primary TB being what most people think of when they think of TB) immediately, your chance of doing so later is around 10% (possibly as low as 5%).

If you've had primary TB, then the foci of that infection is now a wee calcified lump in your lung, neatly sealed off. It's not going to infect anyone. In active TB, there are cavities in the lung breeding more TB to spread around: TB is airborne, and spread by droplets from the person coughing or sneezing (occasionally by spitting, singing and other sorts of projecting activities). So if you don't have a cough, it's both less likely that you have active TB, and even if you did, you're spreading it less.

In summary: it is highly unlikely that you will progress to post-primary TB. In the unlikely event that you do progress, the likelihood is that you'll have obvious symptoms, like a cough and enlarged lymph nodes. So the simplest thing to do is avoid contact with your friend when you feel ill, especially respiratory ill (which would probably be a good idea anyway), and if your symptoms linger then get them checked out.

If you get treatment, for the love of god take it for the full six months. We really don't need any more multi-drug resistant TB.
posted by Coobeastie at 9:38 AM on October 7, 2009

Because my grandfather was in an iron lung, I've tested positive for TB since the day I was born.

That sentence makes no sense. An iron lung was a general treatment modality, not a specific one. He may have had active (catchable) TB, but he might have had any number of other diseases.

Maybe you had a BCG. BCG invalidation of TB skin tests is usually null after childhood. (BCG protection usually is too.) If you're in the US, you probably didn't, though; it's very rare here since the US is considered a low-risk country.

The current suggestion for someone in your case is not to do anything, as:
1. You have no real known risk factors because you do not know what disease you were exposed to - and if he was in an iron lung, I don't know how exposed you even would have been. As you describe yourself as a healthy-normal, so unless you're not telling us about the months you spent in prison, then you have no risk factors.

2. You have no symptoms.

If you end up working in healthcare or prison or some other case where they want to do a skin test, ask if they can do a Quantiferon (blood) test instead.

The US, versus most countries, does like to treat for latent TB, but it's 9 months of daily, liver-hurty, meds (and 9 months dry, as a result.) The reactivation rate is relatively low, and that's IF you have latent TB at all. You don't really know for sure, not with what seems to me to be a distant memory of 'always positive'. We don't even treat latent in the general population unless the Mantoux (not tine) is > 10 mm, and in your case, they might not even recommend it.

You sholdn't cough on your immunocompromised friends anyway, but LATENT TB DOES NOT SPREAD. If we had to treat everyone who came into contact with a latent case, well, then, we'd all be treated all the time.
posted by cobaltnine at 9:42 AM on October 7, 2009

Thanks for your replies! Sorry for not being more clear: my grandfather had ACTIVE TB that was so bad, he almost died and he had to be hospitalized for a long, long time in an iron lung. We're talking years. My mother contracted it from him, and she passed it in utero to all her children. That's what I was told, hence the question. I know latent TB doesn't spread, I'm just concerned about it going active one of these days without me knowing it. Thanks again!
posted by aquafortis at 10:28 AM on October 7, 2009

Please ignore just about everything that was posted above. I am an academic pulmonologist, and can assure that if nothing else, the advice you are receiving here is largely counter to the standard of medical care as recommended by the latest guidelines of the American Thoracic Society, Infectious Disease Society of America, and Centers for Disease Control.

A few points to correct:

1. The tuberculin skin test has varying cut-points depending on risk stratification. That does NOT mean that a positive test if interpreted appropriately in a low-risk patient is a false positive.

2. Latent tuberculosis infection (LTBI) IS treated in the United States.

3. Treatment of LTBI rarely does cause liver problems, but this is an exceedingly rare and overstated complication that leads to even more exceedingly rare failure to recover completely with appropriate follow-up.

4. In an adult, prior BCG (which you probably did not receive) as a child is essentially irrelevant in the interpretation of TB skin tests in adults.

5. A patient in an iron lung with tuberculosis is just as contagious as someone who wasn't in an iron lung.

6. It's true that the highest risk of activation in the setting of LTBI is within the first year or so of exposure, and that the overall lifetime risk of developing active TB may well be 10% or less. That doesn't necessarily mean that treatment for LTBI isn't warranted both at the level of the patient and as a public health issue. If you do develop active TB, the therapy is significantly more arduous, and you will place many people (including loved ones and coworkers) at high risk of developing active disease. That's why the IDSA, ATS, and CDC guidelines reflect the belief that in general, the risks and inconvenience of therapy for LTBI are outweighed by the benefits of therapy.

In summary, you need to talk to your doctor about this and not the internet.
posted by drpynchon at 10:47 AM on October 7, 2009 [11 favorites]

Oh, hey, good, a qualified person showed up. Yeah, people giving medical advice over the internet would be well advised to remember that 10% of a lot of people is still a lot of people. Also, um,

My mother contracted it from him, and she passed it in utero to all her children.

This sounds kind of crazy. My understanding is that congenital TB is very, very rare.
posted by molybdenumblue at 11:19 AM on October 7, 2009

Yeah, people giving medical advice over the internet would be well advised to remember that 10% of a lot of people is still a lot of people.

People giving statistical advice over the internet should probably check their work: 1) one individual having a 10% lifetime chance of developing active TB is not the same as 10% of people with latent TB developing active TB. 2) I'm not sure where the "lot of people" number comes from, but the case rate for active TB in the US is <5>
I won't argue with drpynchon, but I will point out that my ppd converted while I ran an HIV clinic. I got a clear xray, and I was advised that taking the prophylactic measures was entirely my own decision by the very strict infection control officers at the hospital to which we were attached.
posted by OmieWise at 2:57 PM on October 7, 2009

should read: "the case rate for active TB in the US is less than 5 per 100,000.
posted by OmieWise at 3:04 PM on October 7, 2009

1) one individual having a 10% lifetime chance of developing active TB is not the same as 10% of people with latent TB developing active TB.

Well, of course we can't say that 10% of all people with latent TB will develop active disease (although the number is based on studies where just that did more or less happen), but I don't see where I said that. I just wanted to point out that 10% is actually a pretty significant risk. That's not too far off the lifetime risk of breast cancer, so let's nobody worry about getting mammograms?

2) I'm not sure where the "lot of people" number comes from, but the case rate for active TB in the US is [less than 5 per 100,000.]

"Estimated LTBI prevalence was 4.2%; an estimated 11,213,000 individuals had LTBI."
posted by molybdenumblue at 6:21 PM on October 7, 2009

Well, of course we can't say that 10% of all people with latent TB will develop active disease (although the number is based on studies where just that did more or less happen), but I don't see where I said that.

10% of a lot of people is still a lot of people
From your cite: Conclusions: In addition to basic TB control measures, elimination strategies should include targeted evaluation and treatment of individuals in high-prevalence groups, as well as enhanced support for global TB prevention and control.

Such a great opportunity to recommend across the board treatment for latent TB, and it wasn't taken. The internet is such a strange place.
posted by OmieWise at 7:09 PM on October 7, 2009