Approach to positive PPD?

[Saman49]

---

Members do not see this ad.

Can somebody help me with this Question?

I know previous BCG vaccine will cause false positive PPD.
Approach is if pt have reactive PPD take X-ray and culture to rule out Active. If it is not active then Tx for latent T.B is 9 month INH.

So my Q is if somebody had vaccine and is false positive for PPD without X-ray manifestation should get 9 m INH???

That just doesn't make sense 🙁

 

[Lacktherof]

Can somebody help me with this Question?

I know previous BCG vaccine will cause false positive PPD.
Approach is if pt have reactive PPD take X-ray and culture to rule out Active. If it is not active then Tx for latent T.B is 9 month INH.

So my Q is if somebody had vaccine and is false positive for PPD without X-ray manifestation should get 9 m INH???

That just doesn't make sense 🙁

I believe in this case it would be based on whether or not the person had recent exposure, especially if the pt is immunocompromised (i.e. HIV+). Someone correct me if I'm wrong

 

[StrangerX]

You use the same guidelines for BCG vaccinated patients as for non-vaccinated patients. Here in the US of A we don't trust the BCG vaccine because it is variable in efficacy and can cause false positives...so we don't give it. You wouldn't know it was false positive unless you used the gold standard test.

It may become tricky if they include a quantiferon assay as an answer choice as I'm not sure whether you would pick that to rule out the possibility of a false positive. I suppose the morbidity of the 9 month therapy would be outweighed by potentially narrowing down the population who you treat, so it could be justified to do it.

 

[futuredoctor10]

It may become tricky if they include a quantiferon assay as an answer choice as I'm not sure whether you would pick that to rule out the possibility of a false positive. I suppose the morbidity of the 9 month therapy would be outweighed by potentially narrowing down the population who you treat, so it could be justified to do it.

Right as Stranger X mentioned, we ignore the fact that a patient is vaccinated with BCG in the US with regards to PPD screening.

If the patient has a positive PPD and had a BCG vaccine in the past, and the question asks for next best step and offers the interferon-γ release assay, then I think you could pick that as the choice to "rule out" false positive.

Otherwise if that is not an option, you ignore the BCG vaccine and basically assume & 'treat this as a positive PPD.

 

[mvenus929]

The problem with patients who have received BCG vaccines is that they also lived in an area where TB was endemic, so they are at a higher risk of acquiring TB in the first place. Combined with the fact that the vaccine isn't very effective, it's impossible to say without doing a quantiferon whether it's a false positive or not.

The policy at my hospital is that we just assume that they were exposed, and provide the treatment. Then they're covered whether the vaccine was effective or not. I'm not sure how the USMLE would write the question, but in practice, you certainly would not be wrong in treating them.

 

[evilbooyaa]

As an example, I had a friend who received the BCG vaccine, and when he needed a PPD for med school, it was positive, he had a negative CXR, and still had to get INH for 9 months.

 

[CDI]

My micro may need work but IIRC, BCG vax is to fight against disseminated TB (extrapulmonary). Not that useful in those who are immunocompetent otherwise.

Makes sense you treat everyone, regardless of vaccine status for that very reason. Someone who has been "vaccinated", can still get pulm TB.

If it was truly that effective, the US would have made it mandatory. (As its clearly not eradicated.)

 

[drk]

One of the textbooks I read in Med school said the efficacy of BCG ranges from 0 to 88% 😛

 

[Saman49]

Thank you everyone 🙂

 

[CDI]

One of the textbooks I read in Med school said the efficacy of BCG ranges from 0 to 88% 😛

Well, we did study in the same country.