How Long Is a Tuberculosis (TB) Test Good For?

Whoever asks for a TB test decides how long it is good for, since 2023 CDC guidance sets no expiry date. Under 2023 CDC rules, a negative skin test recorded in the past 12 months can serve as step one of two-step testing. Check the exact rule with your employer or school before you book a new test¹.

How often you need a new test is a separate question. The guide to how often you need a TB test covers yearly and one-time testing.

At work, your employer and state rules decide how long a TB test is good for. CDC guidance from 2019 asks health care workers for a test at hire, with no routine yearly tests without exposure. After an exposure, a worker whose test is negative is tested again 8 to 10 weeks after the last contact². Under 2019 CDC guidance, the same type of test is preferred². CDC guidance from 2023 says its recommendations do not override or replace state regulations⁷. Under that 2023 guidance, a worker with untreated latent TB infection gets a yearly symptom check, not a new test⁷. CDC guidance from 2019 lets facilities consider repeat screening for higher-risk groups, such as pulmonologists and respiratory therapists². The same applies to settings such as emergency departments where TB has spread before². All health care personnel get TB education every year, under 2019 CDC guidance². The paperwork for a tuberculosis (TB) test for employment usually states the time limit the employer uses.

For college, a TB test is accepted if it was done within six months before you start, under ACHA guidance. ACHA also says students at low risk on the questionnaire should not be tested at all. For students who do need a test, ACHA prefers the TB blood test³. Below college level there is no national rule. Minnesota health department guidance from 2022 says screening every student and staff member is not recommended. Rules for a TB test for school are set by each state and district.

A TB blood test result, like a QuantiFERON, has no expiry date in 2024 CDC testing guidance either. It shows your status on the day of the blood draw, and the place asking sets how recent it must be. A positive blood test is not repeated to clear you later, because a positive result can stay positive⁶. CDC guidance from 2024 names the two FDA-approved TB blood tests in the US, QuantiFERON-TB Gold Plus and T-SPOT.TB⁸. Unlike a skin test, a blood test does not boost the result of a later test, under 2025 CDC guidance⁵. A CDC report from 2019 says switching between skin and blood tests in repeat testing might look like a new infection. Your QuantiFERON results report states the date of the draw, which is the date the place asking will check.

A TB skin test result is valid for as long as the asking employer or school accepts it. A skin test left unread past 72 hours is rescheduled as a new test, under 2025 CDC guidance. In two-step testing, the second step is placed 1 to 3 weeks after the first is read¹. CDC guidance from 2023 says skin tests can be repeated at any time, with no general health risk¹. Each skin test is read 48 to 72 hours after it is placed, under 2025 CDC guidance⁵. The two-step skin test is used when a skin test is the baseline test for a new job.

A two-step TB test has no CDC expiry; 2023 CDC guidance uses it for the first skin test of adults tested periodically. It lowers the chance that a boosted reaction, from an infection long ago, is read as a new infection on later tests. Under 2023 CDC guidance, a second test not read within 48 to 72 hours is placed again as soon as possible¹. That holds even if several months have passed¹. A TB blood test used as the baseline needs no second step, under the same 2023 CDC guidance¹. States can set their own rules. South Carolina law S.558, signed in 2024, covers new nursing home residents. A resident with a negative skin test in the 12 months before admission needs only a single skin test. The same law lets the facility use one TB blood test in place of the two-step test.

A chest X-ray for TB follows a positive test, and 2024 CDC testing guidance sets no fixed time it stays valid. It shows the lungs on the day it is taken, so the employer or doctor decides when a new one is needed. CDC guidance from 2023 says health care workers need no repeat chest X-ray without new reasons¹. Those reasons are TB symptoms or starting latent TB treatment¹. A chest X-ray for tuberculosis checks for active TB of the lungs, the form that is contagious⁶.

For a US green card medical exam, every applicant aged 2 or older needs a TB blood test from a civil surgeon. A chest X-ray is added if the blood test is positive or the applicant has HIV or TB symptoms. CDC instructions from 2024 say the TB tests and any X-ray are ordered and done at the time of the exam⁴. Exam parts must be less than 1 year old when the civil surgeon signs Form I-693⁴. A previous positive blood test is accepted with written documentation from a physician⁴. A previous positive skin test still needs a blood test⁴. The USCIS Policy Manual covers forms signed on or after November 1, 2023⁹. Such a Form I-693 counts while the application it was filed with is pending⁹. A form signed before that date counts for 2 years from the civil surgeon signature⁹. If the application is withdrawn or denied, a new Form I-693 is needed for any future application⁹. The civil surgeon records the results on the tuberculosis test form for the exam.

California rules depend on the job: some health facilities test every year, and school staff are reassessed at least every four years. Skilled nursing facilities must include a TB infection test in the annual health exam, under Title 22, section 72535. The California Department of Public Health table also lists at least annual testing for acute psychiatric hospitals and chemical dependency recovery hospitals. Its rows for general acute care hospitals, home health agencies and adult day health centers do not mention annual testing. Education Code section 49406, in the version in effect since January 1, 2024, covers new school employees. Each needs a TB risk assessment from the past 60 days, and an exam if risk factors are found. After a documented positive test followed by an X-ray, the risk assessment is no longer required. The employee files a certificate from the examining clinician showing they were found free from infectious TB. The school form is a risk assessment questionnaire about where you were born, travel and exposure.

In Pennsylvania schools, new staff need a TB test given within three months before the school receives their test form. Staff with a documented nonsignificant result need no further tests unless exposed or directed by the Secretary of Health. The rule covers employees, contractors, student teachers and volunteers in direct contact with students 10 or more hours a week. Students are tested on first entry to school and in grade nine, under Public School Code section 1402(a)(4). Since a November 1997 joint letter, school boards may apply to drop student testing or to test only high-risk students.

These questions cover positive results and one more state rule.