How to Read Tuberculin Skin Test?

Step 1

Measure the induration, not the redness

Step 2

Read the test 48 to 72 hours after placement

Step 3

Use a ruler to measure the widest transverse diameter of the indurated area in millimeters

Step 4

Do not measure erythema

Step 5

Interpret 5 mm as positive in:

Step 6

HIV infection

Step 7

Recent close contact with active TB

Step 8

Chest X-ray evidence of prior TB

Step 9

Organ transplant recipients

Step 10

Immunosuppressed patients

Step 11

Interpret 10 mm as positive in:

Step 12

Recent immigrants from high TB prevalence countries

Step 13

Injection drug users

Step 14

Residents and employees of high-risk congregate settings

Step 15

Mycobacteriology laboratory workers

Step 16

People with certain medical conditions that increase TB risk

Step 17

Children younger than 5 years

Step 18

Infants, children, and adolescents exposed to adults in high-risk categories

Step 19

Interpret 15 mm as positive in people with no known risk factors

Step 20

Record the exact size of induration in millimeters

Step 21

If no induration is present, record 0 mm

Step 22

If the test is read after 72 hours, repeat the test if needed

More like this