A TB skin test in Tucson—also called the PPD or 1-step test—places tuberculin under your skin, then a return visit 48–72 hours later reads the result.
How It Works: TB Skin Test
Walk-In
PPD Placement
Get your results when you return in 48-72 hours
What to Expect During a Tuberculosis Skin Test
The skin test uses the Mantoux method — the standard approach for intradermal TB screening.
Here's how your test unfolds:
-
Placement (Day 1): A trained technician injects 0.1 mL of PPD tuberculin solution just below the top layer of skin on your inner forearm. A small raised bubble — a wheal — forms at the site, which is completely normal.
-
Waiting period (48–72 hours): Your immune system needs 48 to 72 hours to respond. If you've been exposed to TB before, immune cells gather at the site and create a firm, raised bump known as induration. Leave the area alone during this stretch — no scratching, covering, or applying anything to it.
-
Reading (around Day 3): A technician measures the induration — the firm, raised area, not the redness.
-
The width of that induration is what determines a positive or negative result under CDC guidelines.
The PPD skin test is recommended by the CDC for TB screening in most healthy adults, and it's accepted by U.S. healthcare employers, schools, immigration authorities, and most occupational health programs.
Comparison of TB Skin Test vs. Blood Test Accuracy
Both tests detect TB exposure, but they differ in accuracy and who they're best suited for.
The TB blood test (IGRA)—like our QuantiFERON Gold—is generally preferred for higher specificity, meaning fewer false positives, especially for anyone who received the BCG vaccine, since BCG doesn't affect blood test results the way it affects the skin test. The PPD skin test remains the standard, preferred option specifically for children under 5, and it's typically less expensive than the blood test. Neither test can tell you whether TB infection is active or dormant on its own.
A positive result on either one is generally followed by a chest X-ray to determine that.
Can the BCG Vaccine Cause a False Positive?
Yes, and this is one of the most common sources of confusion with this test.
Per CDC guidelines, the BCG vaccine may cause a false-positive TB skin test reaction, and there is no reliable way to distinguish a positive reaction caused by BCG vaccination from one caused by true TB infection.
If you received the BCG vaccine (common outside the U.S., sometimes given to infants and children internationally), your skin test may read positive even without ever having TB.
Per CDC guidelines, TB blood tests (IGRA)—like our QuantiFERON Gold test—are the preferred option for anyone with a BCG vaccination history, since blood tests aren't affected by prior BCG.
If you know you received BCG, tell our staff before your test—the blood test may be the better fit for you.
Options for TB Screening If a Skin Test Is Contraindicated
A PPD skin test isn't the right choice for everyone. You should not get a skin test if:
-
You've had a previously documented positive PPD result—repeating it adds no new information and can cause a stronger local reaction
-
You have a documented history of confirmed TB disease
-
You received a live-virus vaccine within the last 6-8 weeks—including MMR, varicella, or yellow fever. The vaccine can interfere with your skin's reaction, leading to an inaccurate result
In any of these situations, our QuantiFERON Gold blood test is the right alternative—one blood draw, no interaction with prior vaccines or a past positive skin test, and no return visit needed for a reading.
Where to Get a PPD / TB Skin Test in Tucson
Right here—Quick Test Health Services of Tucson, just off the I-10 at the St. Mary's Road exit, minutes from downtown. Walk in; no appointment needed. Open at 7 AM Monday-Friday. Note: we do not place TB skin tests on Thursdays, since the test requires a return visit 48-72 hours later for an accurate reading, and we're closed over the weekend—plan your placement for Monday, Tuesday, Wednesday, or Friday instead.
We also serve Casas Adobes, Oro Valley, and Marana.
TB Skin Test FAQ
What happens if I miss the 48–72 hour reading window? The test only counts if it's read inside that window. Past 72 hours the reaction on your arm keeps shifting and can read inaccurately, so a missed reading means starting over — a fresh placement and another two-to-three-day wait. If your timeline is tight, schedule your placement on a day you're certain you can return, or choose the QuantiFERON Gold blood test instead, which is one visit with no return trip.
Can I get the injection site wet or cover it before my reading? You can shower and go about your day normally — water is fine. What you shouldn't do is scratch it, rub it, bandage it, or put lotion or ointment on it, since any of that can irritate the spot and throw off the measurement. Leave it uncovered and untouched until we read it.
What does a positive skin test actually mean — do I have TB? Not necessarily. A positive reaction means your body has been exposed to TB bacteria at some point; it doesn't confirm active, contagious disease on its own. A positive result is typically followed up with a chest X-ray and a provider evaluation to sort out latent exposure from active infection. We'll explain your result and what step comes next.
Does the $35 cover the reading too, or is that extra? Yes—the $35 covers both visits: the initial placement and the reading 48-72 hours later. There's no separate charge to come back and have it read.