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The PPD is a skin test that screens for the presence of antibodies against
tuberculosis proteins.
Tests are normally negative. A positive test indicates current active
infection, previous infection, or enough previous exposure (without clinical
infection) to develop antibodies against tuberculosis.
The test is read 48-72 hours after intradermal injection. The diameter of
induration (the "zone") is measured.
A variety of factors can lead to false positives or false negatives
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Normal Values*
| |
Zone diameter |
| Negative |
< 5 mm |
| Intermediate |
5-10 mm |
| Positive |
>10 mm |
*These are general values taken from a variety of
sources. The actual normal values may vary from lab to lab and from one
type of testing protocol to another.
Watch a video
showing the administration and reading of a PPD skin test
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Source:
Operational Medicine 2001, Health
Care in Military Settings, NAVMED P-5139, May 1, 2001, Bureau
of Medicine and Surgery, Department
of the Navy, 2300 E Street NW, Washington, D.C., 20372-5300
OB-GYN 101:
Introductory Obstetrics & Gynecology
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Brookside Associates, LLC
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