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how to do ppd skin test

how to do ppd skin test

3 min read 30-12-2024
how to do ppd skin test

Meta Description: Learn the proper procedure for administering a PPD skin test, also known as a Mantoux tuberculin skin test. This comprehensive guide covers preparation, injection technique, and reading the results, ensuring accurate tuberculosis screening. This detailed guide covers everything from preparation and injection to interpreting results, ensuring accurate TB screening.

Understanding the PPD Skin Test

The purified protein derivative (PPD) skin test, also known as the Mantoux tuberculin skin test, is a crucial tool for screening individuals for tuberculosis (TB) infection. It doesn't directly diagnose active TB disease but detects the presence of antibodies indicating past or current exposure to Mycobacterium tuberculosis. A positive result doesn't automatically mean active TB; further testing is needed to confirm.

What You'll Need:

  • Tuberculin PPD solution: A standardized concentration, typically 5 TU (tuberculin units) per 0.1 mL, is used.
  • Tuberculin syringe: A 1 mL tuberculin syringe with a 27-gauge needle is recommended for precise injection.
  • Alcohol swabs: For disinfecting the injection site.
  • Gauze pads: For cleaning up any excess solution.
  • Gloves: To maintain sterility and protect the healthcare professional.
  • Measuring device (ruler or caliper): For accurate measurement of induration (hardening) at the injection site.
  • Patient record: To document the test date, time, and results.

Step-by-Step Guide to Administering a PPD Skin Test

1. Patient Preparation:

  • Confirm patient identity: Verify the patient's identity using two identifiers (e.g., name and date of birth).
  • Explain the procedure: Clearly explain the purpose, procedure, and potential risks and benefits of the test to the patient. Answer any questions.
  • Identify the injection site: The inner aspect of the forearm is the preferred site. The site should be clean and free from any lesions or scars.

2. Preparing the Injection Site:

  • Cleanse the area: Thoroughly clean the injection site with an alcohol swab, using a circular motion from the center outwards. Allow the area to air dry completely. Avoid touching the cleaned area.

3. Administering the PPD Injection:

  • Prepare the syringe: Draw up the appropriate dose of PPD solution (0.1 mL) into the tuberculin syringe. Carefully expel any air bubbles.
  • Intradermal injection: Insert the needle bevel up at a 15-degree angle into the cleaned skin. Inject the PPD solution slowly, creating a small bleb (raised wheal) approximately 6-10 mm in diameter. You should see a slightly raised, pearly white wheal. Avoid injecting into subcutaneous tissue.
  • Remove the needle: Withdraw the needle quickly and smoothly. Do not massage the injection site.

4. Post-Injection Care:

  • Document the injection: Record the date, time, site of injection, and lot number of the PPD solution in the patient's chart.
  • Instruct the patient: Instruct the patient to leave the injection site uncovered and avoid scratching or rubbing it.

Reading the PPD Skin Test Results

The PPD skin test is read 48-72 hours after injection. It's crucial to measure only the induration (firm, raised area), not the erythema (redness).

1. Measurement:

  • Use a ruler or caliper to measure the transverse diameter of the induration in millimeters. Measure the area of induration perpendicular to the long axis of the forearm.

2. Interpretation:

  • Negative: Induration less than 5 mm.
  • Indeterminate: Induration between 5 and 9 mm (requires further evaluation based on risk factors and clinical presentation).
  • Positive: Induration of 10 mm or greater. Interpretation depends on individual risk factors (e.g., recent contact with a TB patient, immunocompromised status, recent immigration from a high-prevalence area).

Important Note: Interpretation of PPD skin test results should be done in conjunction with a thorough medical history, clinical evaluation, and possibly other diagnostic tests like chest X-ray and/or sputum culture. The results should be interpreted by a healthcare professional experienced in diagnosing tuberculosis.

Precautions and Considerations

  • Proper training: Only trained healthcare professionals should administer PPD skin tests.
  • Sterile technique: Maintaining strict sterile technique is crucial to prevent infection.
  • Allergic reactions: Although rare, allergic reactions can occur. Monitor the patient for any signs of adverse reactions.
  • False-positive results: Various factors can lead to false-positive results (e.g., previous BCG vaccination, non-tuberculous mycobacterial infections).
  • False-negative results: False-negative results are possible, especially in immunocompromised individuals.

This detailed guide provides a comprehensive overview of PPD skin test administration. Always follow established protocols and guidelines, and consult relevant resources for updated information. Accurate interpretation of results necessitates collaboration with experienced medical professionals. This information is for educational purposes and should not replace professional medical advice.

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