A positive Tuberculosis (TB) skin test (Mantoux test) appears as a firm, raised, and hardened area (induration) at the injection site. This bump is usually measured between 48 and 72 hours after the initial placement. It is important to note that a positive result is determined by the diameter of the hard swelling in millimeters, not by redness, itching, or skin discoloration.
At Sahara West Urgent Care, we specialize in professional TB testing and reading. While a small red mark is common, a provider must physically palpate the area to determine if the reaction meets the clinical threshold for a positive result based on your specific health risk factors.
Key Characteristics of a Positive Reaction
If you are wondering what does a tb test look like if its negative versus positive, look for these signs of a reaction:
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Induration: A hard, dense, and raised bump that you can feel with your fingertips.
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Size Requirements: Generally, a bump of 15mm or more is positive for anyone; 10mm or more is positive for healthcare workers or travelers; and 5mm or more is positive for immunocompromised individuals.
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Redness (Erythema): While often present, redness alone without a hard bump is typically considered a negative reaction.
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Blistering: In rare, severe reactions, a small blister (vesicle) may form, which is usually interpreted as a positive result.
The Diagnostic Process: Why a Professional Reading is Required
You cannot accurately read your own TB test at home. A precise measurement is required to ensure you receive the correct follow-up care. At our urgent care in Las Vegas, our medical team follows a strict protocol for TB screening:
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Physical Palpation: Feeling the margins of the induration to find the exact edges of the swelling.
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Millimeter Measurement: Using a specialized ruler to measure across the forearm (perpendicular to the long axis).
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Risk Factor Assessment: Comparing the measurement against CDC guidelines based on your medical history.
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Follow-up Coordination: If a test is positive, we can coordinate the next steps, such as a chest X-ray or a blood test (IGRA).
Why Choose Sahara West Urgent Care for Your TB Testing?
Sahara West Urgent Care provides reliable, efficient TB testing for employment, school, or travel requirements. We prioritize accuracy to prevent “false positives” that can occur from self-reading. If your test returns positive, we offer the necessary guidance and referrals to ensure you receive the appropriate chest imaging or specialist care quickly and conveniently.
Need a TB test or a professional reading of your current skin test? Book your appointment online or walk into Sahara West Urgent Care today for expert clinical services.
