If a new job, a school placement or a caregiving role has asked for TB clearance, you probably have two questions: which test should you get, and how many trips will it take? This guide to getting a TB test in National City explains how the TB blood test and skin test differ, who each one fits, and what a positive result means.
Why TB Testing Matters in South San Diego County
Tuberculosis is not a disease of the past in San Diego. In its most recent TB fact sheet, the County of San Diego reported 265 new active TB diagnoses, a rate of 8.0 per 100,000 residents and the fifth straight year of increases. The County's South and Central regions have the highest numbers of people diagnosed.
Risk follows exposure. Over the County's most recent five-year period, the TB rate was 2.8 per 100,000 among people born in the United States, 22.3 among people born in Mexico and 41.7 among people born in the Philippines. Those numbers reflect how common TB is where people were born or lived, not anything about a family. For National City's Spanish-speaking and Filipino communities and working families with ties abroad, testing is a practical health step.
Most new cases can be prevented. The County estimates that about 85% of new active TB diagnoses come from long-standing latent TB infection, and its TB elimination fact sheet notes that about 175,000 San Diegans live with latent TB, with only about a quarter aware of it.
Latent TB vs Active TB
TB bacteria spread through the air when a person with active TB in the lungs or throat coughs, speaks or sings. Many people who breathe in the germs never get sick. Instead, the bacteria stay inactive, which the CDC calls inactive or latent TB.
- Latent TB: no symptoms, you do not feel sick, and you cannot spread TB to others.
- Active TB disease: the germs are multiplying and causing illness, and TB in the lungs can spread to others.
Latent TB still matters. Without treatment, about 1 in 10 people with inactive TB will develop active TB disease. Common symptoms of active TB include a cough lasting 3 weeks or longer, chest pain, coughing up blood or phlegm, fatigue, weight loss, fever, chills and night sweats.
When to Go to the ER or Call 911
A TB test is a screening step, not emergency care. Call 911 or go to the nearest emergency room if you cough up more than a few teaspoons of blood, or if coughing up blood comes with chest pain, dizziness or severe shortness of breath, as MedlinePlus advises. If you have had a cough for 3 weeks or more, fever, night sweats or weight loss, tell the clinician before testing. California TB guidance is clear that a negative skin test or blood test does not rule out active TB disease.
TB Blood Test vs Skin Test: Visits, Accuracy and BCG
Both tests look for TB infection. Per CDC clinical guidance, a positive result usually means infection, and more tests are needed to rule out TB disease.
TB Blood Test (IGRA)
The blood test, called an interferon-gamma release assay or IGRA, uses a standard blood draw. The two TB blood tests used in the United States are QuantiFERON-TB Gold Plus and T-SPOT.TB. It takes one visit, and results can be available within 24 hours or take several days, depending on the laboratory.
TB Skin Test (TST)
A small amount of testing fluid is placed under the skin of the forearm. You must return in two to three days (48 to 72 hours) so a trained health care worker can read the reaction. Miss that window and the test has to be repeated, one reason the CDC favors the blood test for people who may struggle to return.
Why BCG Vaccination Matters
BCG is a TB vaccine given to young children in countries where TB is common, and it is not generally used in the United States. BCG can cause a false positive skin test but does not affect the blood test, so the CDC lists the blood test as the preferred test for people age 5 and older who received BCG. California's school TB guidance adds that most people born outside the United States have been vaccinated with BCG.
Who Needs a TB Test for Work, School or Caregiving
MedlinePlus notes that TB screening may be needed when starting a new job or school, after contact with someone who has active TB, and for health care workers. The CDC lists higher exposure risk for people born in or often traveling to countries where TB is common, and for people who work in hospitals, nursing homes, shelters and correctional facilities.
- TB test for employment: if a health care, nursing home or home care employer asks for TB clearance, check the onboarding form for the accepted test and deadline.
- Schools and child care: California law requires a TB risk assessment for K-12 and private school employees, child care center teachers, student transportation contractors, volunteers with frequent student contact and community college employees. If risk factors are found, a TB test and exam follow.
- Volunteering and family caregiving: ask the program what it requires. Children under 5 and people with HIV, diabetes or severe kidney disease have a higher risk of developing TB disease once infected.
What a Positive Result Means and Next Steps
A positive test usually means TB germs are in your body. It does not mean you are contagious. As the CDC explains, additional tests, such as a chest X-ray and a test of the phlegm you cough up, show whether the infection is inactive or active.
- Rule out active TB. Your clinician reviews symptoms and arranges a chest X-ray.
- Discuss latent TB treatment. Once active TB is ruled out, treatment can keep latent TB from becoming disease. The CDC prefers short-course regimens of 3 to 4 months, such as weekly isoniazid plus rifapentine for 3 months or daily rifampin for 4 months, because they are effective, safe and more often completed.
- Keep your records. Save copies of your result and chest X-ray report for future work or school forms.
Getting a TB Test in National City
Palm Urgent Care in National City, at 101 N Highland Ave, Suite F, offers physical exams and lab testing. TB test options can vary, so confirm which TB test this location offers through the National City clinic page or our contact page before you come in. To keep visits to a minimum:
- Bring your employer, school or program form and a photo ID.
- Check whether the form names a specific test (blood or skin) and a deadline.
- Bring past TB test results, chest X-ray reports or BCG history if you have them.
Frequently Asked Questions
Which TB test is better if I had the BCG vaccine?
The CDC prefers the TB blood test for people age 5 and older who received BCG. The vaccine can cause a false positive skin test, but it does not affect the blood test.
How many visits does a TB test take?
The blood test takes one visit. The skin test takes two, because it must be read 48 to 72 hours after placement.
What happens after a positive TB test?
You will need tests to rule out active TB, usually a symptom review and chest X-ray, sometimes a sputum test. If active TB is ruled out, your clinician may recommend a 3 to 4 month course of latent TB treatment.
Does a negative TB test rule out active TB?
No. A negative skin or blood test does not rule out active TB disease. If you have a lasting cough, fever, night sweats or weight loss, get a full evaluation.
Planning a TB test in National City for a new job, a school role or caregiving? Visit the Palm Urgent Care National City page for directions, hours and contact options, and confirm which test your form requires before you come in.
This article is for general information and is not a substitute for medical advice from a licensed clinician.