Who should approve and sign a Purified Protein Derivative (PPD) skin test?

PPD Skin Test Approval and Signature Requirements

PPD test results must be read and documented by designated, trained healthcare personnel—not by patients or healthcare workers themselves—between 48 and 72 hours after injection. 1

Who Should Read and Sign PPD Tests

Qualified Healthcare Personnel Only

• Only trained healthcare practitioners qualified through education and experience should place and interpret tuberculin skin tests. 2
• The Centers for Disease Control and Prevention explicitly states that patient or healthcare worker self-reading of PPD test results should not be accepted. 1
• Designated, trained personnel must perform the reading and document the results. 1, 3

Required Training and Qualifications

• Healthcare practitioners must be qualified as a result of formal education and clinical experience in tuberculin testing. 2
• Personnel must be trained in proper measurement technique, specifically measuring only induration (not erythema) and recording the transverse diameter in millimeters. 1, 3
• Training should include knowledge of the antigen used, immunologic basis for reactions, administration technique, and interpretation criteria. 1

Critical Reading Requirements

Timing

• The test must be read between 48 and 72 hours after injection for accurate results. 1, 3
• Reading outside this window reduces accuracy and may require repeat testing. 3

Measurement Technique

• Only induration (hardened area) should be measured, not erythema (redness). 1, 3, 2
• The transverse diameter of induration must be recorded in millimeters. 1
• Measuring erythema instead of induration leads to incorrect interpretation and inappropriate clinical decisions. 3

Common Pitfalls to Avoid

Self-Reading Is Not Acceptable

• Despite some research suggesting selected patients might accurately self-read tests 4, 5, CDC guidelines explicitly prohibit accepting patient self-readings in clinical practice. 1
• Relying on patient self-reading is unreliable and not recommended by the Centers for Disease Control and Prevention. 3
• This prohibition applies equally to healthcare workers reading their own tests. 1

Documentation Requirements

• The healthcare professional who reads the test must document the measurement in millimeters. 1
• Results should be signed or otherwise attributed to the trained personnel who performed the reading. 1
• Proper documentation is essential for serial testing programs, particularly in healthcare settings where baseline and follow-up comparisons are critical. 3

Quality Assurance Considerations

• Improper administration technique or reading can lead to false-negative results. 3
• The absence of induration with erythema greater than 10 mm in diameter may indicate the injection was made too deeply, requiring retesting. 2
• If significant leakage occurs at the injection site or the injection is administered subcutaneously, the test should be repeated immediately at another site. 2