Schick test

A boy receives an injection of diluted toxin for the Schick test in 1915.

The Schick test, invented between 1910 and 1911^[1] is a test used to determine whether or not a person is susceptible to diphtheria.^[2] 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 an 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 wheal 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:

The test was created when immunizing agents were scarce and not very safe, however as newer and safer toxoids were made available there was no more requirement for susceptibility tests.

References

1. ^ Schick B (1913). "Die Diphtherictoxin-Hautreaktion del Menschen als Vorprobe der prophylaktischen Diphtherie-heilseruminjection". Münchener medizinische Wochenschrift 60: 2608–2610. 
2. ^ Barile MF, Kolb RW, Pittman M (September 1971). "United States standard diphtheria toxin for the Schick text and the erythema potency assay for the Schick text dose". Infect. Immun. 4 (3): 295–306. PMID 4949493. PMC: 416303. http://iai.asm.org/cgi/pmidlookup?view=long&pmid=4949493. 

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