Testing
The TB blood test, and what a positive result actually means
The tuberculosis screen is the part of the exam applicants worry about most. It is also the part most often misunderstood, because a positive result is not a refusal.
Why a blood test and not a skin test
For many years the tuberculosis screen was a PPD skin test, the small injection in the forearm that you returned to have read a couple of days later. CDC technical instructions now require an Interferon Gamma Release Assay (IGRA) blood test for applicants aged 2 and older, and the PPD skin test is no longer accepted as the initial screen.
Practically, this is good news: it is a single blood draw with no return visit to have a result read, and it is not affected by prior BCG vaccination the way a skin test can be.
How it fits into your appointment
The order is written at your visit and you are directed to the collection site. The sample is processed by an outside laboratory, and results typically return within 3 to 5 business days along with the rest of your required laboratory work.
If your result comes back positive
This is the part worth reading carefully, because the fear is usually worse than the reality.
A positive IGRA does not mean you have active tuberculosis, and it does not disqualify you. It means your immune system has encountered the bacterium at some point. Very often that is a latent infection that has never made you ill and never will.
What it does mean is that two further steps are required before your Form I-693 can be completed:
- A chest X-ray.
- An evaluation for active tuberculosis.
We coordinate the imaging locally and walk you through each step. It adds time to your timeline, not an obstacle to your application.
If you have been tested or treated before
Bring the records. Prior TB testing, prior treatment, and any earlier chest X-ray reports are all useful, and they can change what is needed now. This is one of the eight items on our appointment checklist for exactly that reason.
Children under two
The IGRA requirement applies from age 2. For younger children the tuberculosis assessment is handled differently, and the civil surgeon will explain what applies to your child at the visit.
Questions we get about this
Will a BCG vaccination make my result positive?
The IGRA blood test is not affected by prior BCG vaccination in the way a PPD skin test can be. That is one of the reasons it is now the required initial screen.
Do children under two need the blood test?
The IGRA requirement applies from age 2. For younger children the tuberculosis assessment is handled differently, and the civil surgeon will explain what applies at the visit.
Where do I go for the blood draw?
The order is written at your appointment and you are told exactly which collection site to use, so you are not left to arrange it yourself.
This page is general information about a USCIS form, published by a medical practice. It is not legal advice, and NY MedCare is not affiliated with U.S. Citizenship and Immigration Services. Requirements and guidance change, so verify anything date-specific against uscis.gov or with your immigration attorney before you file.