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Nitroblue tetrazolium test
Definition
The nitroblue tetrazolium test looks to see if certain immune system cells can change a colorless chemical called nitroblue tetrazolium (NBT) into a deep blue color.
Alternative Names
NBT test
How the test is performed
Blood is typically drawn from a vein, usually from the inside of the elbow or the back of the hand. The site is cleaned with germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm.
Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.
In the laboratory, the chemical NBT is added to a sample of white blood cells. The laboratory specialist looks at the cells under a microscope and determines if the NBT made them turn blue.
How to prepare for the test
If your child is to have this test performed, it may be helpful to explain how the test will feel, and even demonstrate on a doll. Explain the reason for the test. Knowing the "how and why" may reduce the anxiety your child feels.
How the test will feel
When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.
Why the test is performed
This test is done to screen for chronic granulomatous disease.
Normally, white blood cells called neutrophils make special oxygen compounds that kills bacteria. In chronic granulomatous disease, these compounds are missing. These compounds causes NBT to change from clear to deep blue. If they are missing, the white blood cells will not change color when NBT is added.
Nitro Blue tetrazolium assay Images
