To rule out or not rule out: the TB rule-out

The US is very, very lucky to only have approximately 9,000 cases of TB yearly. But TB can be a “great masquerader” with such serious public health consequences that we have to be constantly vigilant. After all, about ONE-THIRD OF THE WORLD POPULATION is infected with Mycobacterium tuberculosis.

Definitely tuberculosis.

Who needs to be ruled out for TB?

Someone who has clinical +/- epidemiological features of pulmonary TB. Only active pulmonary TB is infectious, so extra-pulmonary TB does not require quarantine. However, extra-pulmonary TB can be infectious if you’re directly biopsying or handling samples from infected lesions.

If the patient in question doesn’t really fit the above features, or you have a strong suspicion for an alternative diagnosis (plain old bacterial pneumonia, pulmonary infarct, DAH, vasculitis, pulmonary sarcoidosis, etc.) then you’re not required to do a rule out. But you better be DAMN SURE because if it turns out the patient does have TB, you could be putting a lot of people at risk of infection.

Who should be put in a negative pressure room “just in case?”

This is a 1999 multicenter, prospective study of a decision instrument to predict who would be at very low risk of TB and would not require isolation. Not surprisingly, people at low risk included those who were not homeless, did not have recent exposure to TB, were not incarcerated, and did not have suspicious x-ray findings. It stands to reason that you might want to be more cautious with people who do have the risk factors outlined above.

Does everyone getting ruled out for TB require hospitalization?

Theoretically, someone can be ruled out for TB at home if they stay away from other family members and don’t go out into the community. This EM:RAP article has a protocol for setting up outpatient TB rule-out. But because YOU CAN’T TRUST ANYONE (and perhaps because the ED doesn’t want to be held liable if something at home goes wrong), I’ve had even very low-public health risk cases admitted for rule-out. If a patient refuses to be admitted, you cannot legally hold them against their will just for TB rule-out, even if they are a public health hazard. Try to convince them of the merits of being admitted, and if they still refuse and leave AMA, call your local health department, who do have the authority to search for elopers and strong-arm them into getting admitted.

What are the possible outcomes for someone exposed to TB?

Can you rule out someone with a PPD or a quantiferon gold?

It would be so much easier than AFB x3 q8H +/- direct sampling! Alas. PPD and quant golds do not distinguish between latent and active TB. A negative PPD or quant gold could be reassuring, but a positive result doesn’t change management. Plus, up to 25% of people with active pulmonary TB will have a negative test result for these two tests.