Oh! The consumption!

March 7, 2006 5:15 PM

Medfilter: Possible tuberculosis exposure. I want to know the answers to some questions that the doctor was unable to provide.

So, my girlfriend received a letter from the county health department saying that she may have been exposed to tuberculosis. It didn't give any clues as to when she may have been exposed, but we received the letter in early January.

She went to the doctor and was administered the Two-Step Mantoux Test. The first time (late January) it was complety negative. 0mm. The second time (March 6th), she got a 12mm reaction.

All the doctor would say was "the textbook says that you have to have 15mm or larger for a positive diagnosis." He wouldn't offer advice on getting loved ones tested, or modifying behavior to limit exposing others (one of our close friends has a toddler we look after occasionally). In fact, he didn't have answers to ANY of our questions.

So, I'm left with some questions. I've been googling around for the past three hours, but still haven't found what I'm looking for.

1) Is it significant that the second test was so much larger than the first? Does this indicate that she was exposed a long, long time ago, or could it mean that she was exposed too recently for the first test to produce a positive?

2) If you have a reaction to one of the shots, does that necessarily mean that you were infected with TB?

3) What does the size of the reaction really mean? The larger the reaction, the more active antibodies you have in your system, and the more active antibodies, the larger the infection?

4) She has none of the symptoms of active tuberculosis. Should she still be super-careful around other people?

5) Should I, her roommate and boyfriend, get tested?

6) Are there any other questions I should ask? :)

Thanks!

posted by anonymous to health (19 comments total)

She didn't by any chance have a foreign childhood, did she?

I got my TB vaccination in France. The vaccination they were using there, at the time I was there (1989-ish?) gives me a terrible reaction every time I get tested for TB.
posted by Jeanne at 5:34 PM on March 7, 2006

you should ask another doctor.
posted by kcm at 5:34 PM on March 7, 2006

Some people react to the TB test after being exposed but never contracting the illness in any sort of meaningful way. (I'm guessing they were slightly exposed and fought off the infection, thereby devloping the anti-TB antibodies that trigger the test, but a doctor could probably give a more correct explanation.)

For instance, my aunt was exposed to TB maybe 50 years ago in elementary school. She never contracted the disease but always reacts to the test (and gets stuck going for further testing to verify that she does not, in fact, have TB).

And yeah, go ask another doctor to make sure.
posted by clarahamster at 5:38 PM on March 7, 2006

She wasn't necessarily exposed. I'd echo what JEanne and clarahamster said. I got a TB vaccine when I was young so I always showed a reaction.

However, a few years ago, I got tested and my reaction was pretty big (~3cm) so the doctor freaked out. She x-rayed my lungs but didn't find anything. I had been exposed to TB in an airport or something. They never told my family members to get tested, but I was put on isoniazid for 9 months just in case.
posted by loulou718 at 5:49 PM on March 7, 2006

Call your local public health department, often a county facility, and ask to speak with a public health nurse or someone at the TB clinic.

1) I don't know enough about the PPD for this one.

2) No, there are several causes of false positive test results.

3) From medicinenet: A small reaction (5 mm) is considered to be positive in individuals with HIV, in individuals on steroid therapy, or in individuals in close contact with a person with active tuberculosis.
Larger reactions (greater than or equal to 10 mm) are considered positive in individuals with diabetes, renal failure and health care workers, among others. In individuals with no known risks for tuberculosis, a positive reaction requires a 15 mm or greater induration.

4) If she has no risk factors for TB, the current guidelines indicate that she doesn't have TB. (I'd be careful saying she has no symptoms of TB; non-pulmonary TB is becoming increasingly common, mostly in immunocompromised individuals.)

5) The conversions from exposure to infection and infection to active disease aren't all that high, as far as I can remember. I beileve the stats are on the CDC website.

6) Call the TB clinic, they'll know this info better.
posted by gramcracker at 6:18 PM on March 7, 2006

My friend, an health educator and outreach worker, says that an Mantoux skin test can only be used to rule out infection. It really is more a of screening test. That is, if you're negative with no significant skin reaction, you do not have TB. But, if you do have a skin reaction, that means that you either have been exposed to TB but have not contracted it, have been exposed and have contracted it, or are a false positive. When there's a skin reaction, a chest x-ray should follow. If the x-ray is clean, there is absolutely no cause for concern.

I learned this when I tested positive after recently. I had been tested several times before with no skin reaction, then I got one. I got a chest xray, and it was clean. My doctor (and my friend the outreach worker and my mother the nurse and my friend's dad the doctor and the nurse who tested me who says she see tons of cases like mine) all say not to worry about it. I could have taken isoniazid, but they said the side effects of the drug weren't worth it for something that was such a not-big-deal.

So, yeah, tell her to see a different doctor who is more willing to explain such things. IANAD, and my explanation probably doesn't quite do the trick.
posted by lalalana at 6:21 PM on March 7, 2006

(whoa... typo city in that post! Apologies!)
posted by lalalana at 6:22 PM on March 7, 2006

go see another doc.

1) not necessarily her situation, but the significance of a boosted second reaction from a second test given within a year of the first could indeed mean a person was "exposed a long, long time ago."

2) see here. note that exposure to TB germs (inactive TB) does not necessarily equate to active TB ("the consumption"). also could be due to a false positive.

3)"Larger the size of induration, higher is the probability of it being due to tuberculous infection." also "The size of the induration reaction correlates to some extent with the probability of TB." The cutoffs for indurations indicating positive is different for people under different conditions, too.

4)...dunno. Can't she ask for a chest x-ray to rule out active tb? That way you can assauge all these fears y'all have.

5) you're probably fine, but why not? If you've got insurance, they should cover a ppd test. If not, it should be cheapish (around $20-$30)

6) ask your doc to not blow off your concerns. jeepers, that was rude of him.
posted by neda at 6:32 PM on March 7, 2006

1) Nope, it's note a problem as soon as it's not bigger than 15 mm, it's just a normal that she got. And the diagnosis of tuberculosis is never based just on the Mantoux Test at all, the patient must have other symptoms (Diaphoresis, anorexia, amenorhe, respiratory symptoms, etc...)

2) Nope, it may and it is most of the time just a natural reaction to a foreign antigen

3) That's the point, if it's very large, it means that the patient have a lot of antibodiees against this antigen and that means (if we have other symptoms) that it may be tuberculosis, it's not enough for diagnosis anyway, other tests are needed

4) not at all, tuberculosis is not like aids or malaria, everyone can get in contact with it but only the weakest ones get the disease (diabetes, aids, extreme stress, infections...), so if your girlfriend have no anorexia and no other symptoms it's not tuberculosis

5) I don't know why, if you have money to give Doctors go ahead

6) Are some doctors stupid ? :)
posted by zouhair at 6:35 PM on March 7, 2006

Go here, a lot of info on all medical conditions
posted by zouhair at 6:37 PM on March 7, 2006

1) No. Not necessarily. These things aren't useful in predicting anything.

2) No. Although it most likely means that you've been exposed to it.

3) No. Think of reality as a Boolean - true (exposure), false (no exposure) - and the test as a crappy analog approximation of a Boolean. 12mm is "pretty likely true exposure."

4) Insufficient data to answer this question.

5) Insufficient data to answer this question.

6) I'm glad you asked. A 12mm PPD following a 'notice of exposure' isn't something to blow off. If I saw a patient in this setting, there'd be some more tests to do. If I were in this position myself, I'd call the Dept. of Health and ask them to recommend a doctor known to be up on the latest guidelines.
posted by ikkyu2 at 7:02 PM on March 7, 2006

Also, to gramcracker:

Kudos for "thinking Bayesian," as you're trained to do. But I think this scenario is perhaps the most eloquent demonstration of where Bayesian thinking falls all to shit.

First of all, you and I can't know the pre-test probability here. Given privacy regulations, it may be that no one is ever allowed to know.

Secondly, look where Bayesian has gotten us in this case. It's produced jarring, terrifying uncertainties about a stigmatizing diagnosis, fears of contagion, and general mayhem among, not only the patient, but her boyfriend, roommates, co-workers, and God knows who else. Bayesian is fine for writing scholarly papers and guiding clinical decision making - inside your own head. When you let it out of that little box and onto your patient, who is a human being with worries, concern, and a vested interest in the outcome, it produces nothing but heartburn.
posted by ikkyu2 at 7:09 PM on March 7, 2006

Friend of mine actually just tested pos for TB (he's a mental health worker in a very rural area . . apparently it's not that uncommon). According to what he told me, if either of you is actually positive (or might be positive) for TB, then you need to use condoms to limit your partner's exposure. I have no other information to back this up, but that's my second hand information. Other than that, talk to another doctor about the TB test. A doctor should be more willing to talk to you than that.
posted by Medieval Maven at 7:10 PM on March 7, 2006

OH, god, somehow my whole stinkin response got wiped out. Here's the short of it:

Yes, she's had a positive reaction. An increase of equal to or greater than 10mm between two tests within two years is a positive reaction.

No, she does not need to isolate herself unless she has signs or symptoms of active TB. She does, however, need to get a chest x-ray to rule out active disease. If the x-ray is negative, she'd be on a prolonged course of treatment for latent TB.

Ok, lemme try this again:

1) Is it significant that the second test was so much larger than the first? Does this indicate that she was exposed a long, long time ago, or could it mean that she was exposed too recently for the first test to produce a positive?
Maybe, maybe, and maybe. But the bottom line is that she's had a positive test. An increase of 10mm between two tests within two years is positive, regardless of baseline.

2) If you have a reaction to one of the shots, does that necessarily mean that you were infected with TB?
No. False positives are a possibility.

3) What does the size of the reaction really mean? The larger the reaction, the more active antibodies you have in your system, and the more active antibodies, the larger the infection?
Just has to do with immune response to antigens, in this case, the protein involed with the test. If you google up "delayed hypersensitivity" or "Mantoux reaction," you can read about the physiology of the reaction.

4) She has none of the symptoms of active tuberculosis. Should she still be super-careful around other people?
No. But she should watch for any symptoms.

5) Should I, her roommate and boyfriend, get tested?
If you want. I'd say no. If you're going bananas thinking about it, go for it. But keep in mind that you can have false positive and negative results, that you have no signs of active TB, that you're not even sure if you have any risk factors of exposure as your girlfriend may not have an active infection.

6) Are there any other questions I should ask? :)
Yes. Ask the health department what the nature of exposure was. This helps stratify risks and provides a good bit of history. Regardless, it doesn't change what must be done.

So the short version:
- Yes, she's positive.
- No, she doesn't need to isolate herself.
- She should get a chest x-ray.
- She should watch out for symptoms.


If she exhibits any signs or symptoms of active TB, or if the chest x-ray is positive, she must isolate herself, give some sputum samples, and start treatment. If the sputum tests are negative and/or she responds to treatment favorably, isolation can be discontinued.

If the chest x-ray is negative, again, she'll have to be on a prolonged course of treatment for latent TB. During this time, she does not have to isolate herself.
posted by herrdoktor at 7:25 PM on March 7, 2006

Condoms? I'd be more concerned about a face mask then condoms with somebody who has TB than a condom. The whole reason that the letter was sent out was that it could be quite contagious as an airbourne virus.
I'm actually quite surprised that he didn't order an x-ray after a reaction post-exposure. I wonder if cost was an issue with this. I would definately see another doctor to at least get some answers as to why they feel it wasn't necessary to take any other measures. Perhaps, was the area just 12mm of redness?
posted by Iamtherealme at 7:37 PM on March 7, 2006

Due respect to those above, Pulmonology is my bread and butter.

1) It likely means that she was exposed too recently for the delayed-type hypersensitivity reaction of the skin test to manifest itself. And indeed, a 10mm increase between successive tests over 2 years is considered a positive result.

2) If you have a reaction, it means that you’ve quite likely been exposed to TB and your body has mounted an immune response to the bacterium. There are however rare false positives. You may or may not have ongoing latent TB as in the majority of people the immune system eradicates the bug. That said, approximately 10% of patients with a positive skin test ultimately develop active TB, and half of those develop it within 2 years of skin test conversion.

3) This is a difficult question to answer, however in the case of your girlfriend, based on a known recent exposure, 5mm really should be the cutoff. Your doctor appears to have misinterpreted the CDC’s recommendations regarding risk stratification for PPD tests. Moreover, depending on where you’re from many local health departments set stricter cutoffs depending on the prevalence of TB. In many of these areas, Los Angeles for example, anyone with indurations greater the 10mm may be considered positive. Let me also note that many people, doctors even, don’t know how to properly read a PPD test, and if your doctor can’t interpret the results he may likely be one of these people.

4) No. If she has no symptoms, she isn’t contagious. Right now at least.

5) No. Not unless you guys also were exposed to someone with active TB.

6) Yes. You should ask that she get treated for latent tuberculosis, as this is what the CDC recommends. Treatment reduces the risk of developing active TB by approximately 2/3 to 3/4.

Also, the value of a chest x-ray in an asymptomatic person is actually quite minimal in that it probably won't alter the appropriate medical management of such a patient. But a baseline x-ray, for reference sake is probably a good idea.

In short, see another doctor, a Pulmonologist or Infectious Disease specialist if you can't find a general practitioner who knows the appropriate guidelines.
posted by drpynchon at 11:59 PM on March 7, 2006

Drpynchon, you're a great guy, and if I had TB, I'd want you on my case. But how do you know the person in question's really asymptomatic, or even knows what the typical symptoms are? For that matter, how do you know she doesn't have Behcet disease and what was read as a 12mm PPD wasn't just pathergy?

If someone goes to a doctor and "asks to be treated for latent tuberculosis," that doctor might just write a scrip for 9 months of isoniazid. And prophylactic isoniazid killed a friend of mine, a medical resident with a brilliant future ahead of him, via its notorious and not terribly uncommon side effect of fulminant hepatic failure.

This internet thing isn't a doctor's office. Be careful what you do, and I'm addressing that comment to anyone - any doc, any patient - who cares to read this.
posted by ikkyu2 at 1:22 AM on March 8, 2006

It's a fair point ikkyu2. I can't say for certain whether the person in question has active TB. That said, the person just received notice of exposure, went to see a doctor based on this notice and was once evaluated (granted by someone may not be up-to-date on PPD testing), and there are no comments on symptoms. Indeed, if she has symptoms consistent with active TB she should be treated as such, and I can't know that for sure. So anon, be sure that a physician or at least someone from the health department has evaluated her for symptoms consistent with TB. It's probably presumptuous to assume similar management elsewhere, but for what it's worth, at least in LA county, reported cases of TB lead to a pretty thorough contact investigation by the county which is aimed in part at finding other active cases.

Now, to address the second issue (and this is purely academic and probably more than the asker was asking for but). Fulminant hepatitis can indeed be a fatal complication to INH as you well know. That said, the latest studies have suggested that the concerns over this matter were overblown on an epidemiological level, so much so that the CDC no longer recommends potentially deferring treatment for latent TB in those over 35 (as was previously the practice). The latest research estimates that combined with routine follow-up, the incidence of INH hepatitis is approximately 0.1% over a full course. In all-comers, with severe INH hepatotoxicity, the prior quoted mortality rate was 10%, and in the study I just referred to by Nolan et al in JAMA in 1999, in over 11,000 patients, 11 developed clinically significant hepatitis, only 1 required hospitalization, and there were no deaths (again in the setting of the appropriate recommended followup).

At this time, the only true contraindications to treatment with INH (and these are deemed "relative" per the CDC) are active hepatitis or end-stage liver disease. With all patients on long term INH, the CDC recommends monthly evaluation and followup, but even so the CDC doesn't recommend routine monitoring of liver enzymes unless the patient has suggestions of liver disorder on initial evaluation, has HIV, is pregnant, or is in the immediate post-partum period.

In the case of someone who has Behcet's disease, I still believe after a known exposure, followed by conversion on skin test over 6 months, the CDC (and I personally) would still strongly recommend empiric treatment. As a sidenote, while positive pathergy may theoretically mimic the induration found with PPD testing, I suppose, it generally tends to have a different appearance -- classically papulopustular as opposed to the induration with surround erythema one typically finds following positive PPD placement. I've probably examined pathergy on about 15 patients with Behcet's and none looked quite like a positive PPD response. Behcet's pathergy also has a component of tenderness less notable with PPDs. As a learning point to other readers, the essential part of reading PPDs is the induration or well demarcated area of firmness at the site -- not the redness. Moreover with PPDs the diameter should be measured across and not along the arm. If you see a nurse measuring redness or along the arm, ask for someone else to read your PPD.

I'm sad to hear about your friend. I can tell you that I've treated 2 people with fulminant INH hepatitis in-house who both survived, and have read about and heard of a fair number of other severe cases. It's obviously no solice to someone who's lost a friend this way, but virtually all cases of this sort of severe reaction (which I should again stress to other readers is exceedingly rare) were due to either lack of follow-up (as may be inferred from Nolan's work) and continued use of INH in the setting of progressive jaundice or pregnancy.

You're right that "asking that she get treated" is probably too strong. But in all likelyhood it is the case, and I'd hope that no doctor would write a nine month script for INH without follow-up based on some advice a patient got on the internet. Let me reiterite to those reading, implicit in treatment for latent TB is regular scheduled follow-up with a physician. With the appropriate follow-up this treatment is quite safe, but without it one runs a significantly increased risk of developing a complication.

The long-and-short of it is again, anon, your girlfriend probably doesn't have active TB (though I can't be sure), but she certainly hasn't gotten the appropriate medical management. She needs to see someone else about this.
posted by drpynchon at 5:15 AM on March 8, 2006

Now we're on exactly the same page, DrP.

Yeah, this guy should've known better. He apparently didn't discontinue his fairly heavy alcohol use with the INH like he was supposed to, either, so by the time the hepatitis was diagnosed his liver was pretty much toast.
posted by ikkyu2 at 10:53 PM on March 8, 2006