TB test readings

Have you taken a class through ALA? That would be your best bet.

A positive test not only depends on the size of the induration, but on the person being tested.

Here, I grabbed this off the 'net:

A small reaction, called an induration, at the site of the test (5 to 9 mm of firm swelling) is a positive result in people who:

• take steroids
  
• have HIV
  
• have received an organ transplant
  
• have a weakened immune system
  
• have been in close contact with someone who has active TB
  
• have changes on a chest X-ray that appear to be the result of a previous TB infection
  

Members of this high-risk group may require treatment, but a positive result doesn't always mean that they have active tuberculosis. More tests are necessary to confirm the diagnosis.

Larger reactions (10 mm of swelling or more) are a positive result in people who:

• have had a negative PPD skin test in the past two years
  
• have diabetes, kidney failure, or other conditions that increase their TB risk
  
• are healthcare workers
  
• are intravenous drug users
  
• are immigrants who have come from a country that's had a high TB rate in the past five years
  
• are under age 4
  
• are infants, children, or adolescents who have been exposed to high-risk adults
  
• live in certain group settings, such as prisons, nursing homes, and homeless shelters
  

For people without a known risk factor for TB, a 15 mm or larger firm swelling at the injection site indicates a positive reaction.

We used to take an ink pen and mark the outside of the induration (the raised area) and measure from one pen mark to the other. The important thing is to be sure that you measure from the widest points, because the induration isn't always a nice little circle. It may only be 4 mm across one way, but 12 mm if measured at the widest point. It's not rocket science, but it does take practice. Oh, and make sure you only measure the induration. Sometimes the red mark is huge but the induration is tiny or non-existent.