Help me out here....

Forgive me if the answer is 'no,' but is this a homework question? The reason I ask, is that it is kinda a strange question to be asking. If it not homework, why are you asking it? Not trying to sound accusatory, just looking for more context.

It's not homework. I had to request records on this person for my workplace and I was hoping they had tested the fluid, because a doc has now ordered me to collect sputum. However the patient has been on LTBI medication for three weeks so I think collecting sputum is pretty futile at this point.

a chest tube for a pneumothorax is to mainly allow air to escape and thus the lung to re-inflate... any fluid collected is not likely to be directly from the lungs and since it passes through the water seal it would be extremely diluted. I have never personally heard these fluids being tested, but guess they could be however I just don't know as I'd trust the results.

Expectorated sputum, especially from a deep cough, is the best material to test. He could be wanting to test to make sure that the meds have worked and the patient does not currently have any form of active TB.

The meds for active tb are more intense than ltbi. Even on the right active tb meds, the sputum can remain positive for weeks. I think it's still within a reasonable window for a sample collection.

It's reasonable. Those antibiotics are unlikely to impact the results and the fluid from the chest tube isn't the same as sputum but..... I thought Mexico vaccinated? If they have that vaccine scar then they'll always test positive and since I know darn well the patient has had multiple chest x-rays (and if they showed a TB issue someone would have said) then... so, it depends on if he has the vaccine scar.

a chest tube for a pneumothorax is to mainly allow air to escape and thus the lung to re-inflate... any fluid collected is not likely to be directly from the lungs and since it passes through the water seal it would be extremely diluted...

[...]

I'm curious, as I've not seen this, what type system you're using in which the water seal is between the patient and collection device.

Thanks.

any fluid collected is not likely to be directly from the lungs and since it passes through the water seal it would be extremely diluted.

Could you clarify what you mean by this?

ETA - sorry. I see the question has already been asked.

It's reasonable. Those antibiotics are unlikely to impact the results and the fluid from the chest tube isn't the same as sputum but..... I thought Mexico vaccinated? If they have that vaccine scar then they'll always test positive and since I know darn well the patient has had multiple chest x-rays (and if they showed a TB issue someone would have said) then... so, it depends on if he has the vaccine scar.

There is a theoretical risk that BCG vaccination can cause false positives on TSTs. However, BCG effect usually wears off many years before an adult pops positive on a TST. I have had BCG vaccinated patients who've had minor reactions to skin tests (5-10 mm) who were negative on a subsequent Quantiferon Gold, but if a person comes into my clinic with more than 15 mm, that's a true positive. They're infected.

The meds for active tb are more intense than ltbi. Even on the right active tb meds, the sputum can remain positive for weeks. I think it's still within a reasonable window for a sample collection.

This person is 1/4 complete on a 3HP regimen. It's not like he only took three weeks out of nine months of Isoniazid.

However, you are right the sputum can remain positive several weeks into the RIPE regimen, and even longer if you're dealing with MDR or worse.

I'm curious, as I've not seen this, what type system you're using in which the water seal is between the patient and collection device.

Thanks.

This not only shows the system in question, but how to avoid dilution.

What- are some of you guys using something else?

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This not only shows the system in question, but how to avoid dilution.

What- are some of you guys using something else?

Nope, that's exactly what I would do.