Schick test

 

diagnostic test designed to evaluate susceptibility to diphtheria. A small amount of diphtheria toxin is injected into the skin; the injection will produce an area of redness and swelling in individuals with low levels of antibody (i.e., little immunity) against the toxin. If the individual is immune to diphtheria, the antibody in the system will neutralize the toxin and no skin reaction will occur.

The Schick test, invented between 1910 and 1911, is a test used to determine whether or not a person is susceptible to diphtheria. It was named after its inventor, Béla Schick (1877-1967), a Hungarian-born American pediatrician. The test is a simple procedure. A small amount (0.1 ml) of diluted (1/50 MLD) diphtheria toxin is injected intradermally into the arm of the person. If a person does not have enough antibodies to fight it off, the skin around the injection will become red and swollen, indicating a positive result. This swelling disappears after a few days. If the person has immunity, then little or no swelling and redness will occur, indicating a negative result.

Results can be interpreted as:

1. Positive: when the test results in a wheel of 5-10 mm diameter
2. Pseudo-positive: when there is only a red colored inflammation and it disappears rapidly
3. Negative reaction:
4. pseudo negative reaction:

References

• Taber's Cyclopedic Medical Dictionary, 20th Ed. (2005).

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