Page last updated April 2020

This is a FREE resource designed to support the medical profession in their care of women made possible by over 750 expert clinicians who are generously providing their contributions without any remuneration and by the publishers who have paid personally for the creation of this site in the memory of their daughter, Abigail.

Current Authors


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

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.