The Dick test assesses susceptibility to scarlet fever. This skin test, developed in 1924, determines immunity by injecting scarlet fever toxin and observing skin reactions.​

Correct Answer

(B) scarlet fever
The Dick test involves intradermal injection of diluted scarlet fever toxin from Streptococcus pyogenes. A positive reaction (redness >10 mm after 24 hours) indicates susceptibility due to lack of antibodies, while no reaction shows immunity.​

Option Analysis

• (A) Diphtheria: Incorrect. The Schick test assesses diphtheria susceptibility using Corynebacterium diphtheriae toxin. A positive reaction (redness after 3-4 days) signals lack of immunity.​

• (B) Scarlet fever: Correct. This test specifically detects susceptibility to scarlet fever toxin, guiding immunization in the pre-vaccine era.​

• (C) Typhoid fever: Incorrect. The Widal test diagnoses typhoid via serum agglutinins against Salmonella typhi, not susceptibility assessment.​

• (D) Tuberculosis: Incorrect. The tuberculin skin test (Mantoux) detects TB exposure or latent infection via induration to purified protein derivative.​

Dick Test Susceptibility Scarlet Fever: Essential Guide for CSIR NET Aspirants

The Dick test susceptibility scarlet fever question frequently appears in competitive exams like CSIR NET Life Sciences, testing knowledge of diagnostic immunology. Developed by George and Gladys Dick in 1924, this intradermal skin test revolutionized scarlet fever management by identifying susceptible individuals before outbreaks.​

How the Dick Test Works
A small dose (0.1 ml) of scarlet fever toxin, produced by Streptococcus pyogenes, is injected under the skin. Read after 24 hours:

• Positive (redness/swelling >10 mm): Susceptible—no antitoxin antibodies present.

• Negative: Immune from prior infection or vaccination.​
  This mirrored the Schick test for diphtheria but targeted erythrogenic toxin specific to scarlet fever.​

Why Not Other Options?

• Diphtheria uses Schick test for toxin reaction.​

• Typhoid relies on Widal for antibodies, not pre-immunity.​

• Tuberculosis employs Mantoux for latent infection.​

Historical Relevance for Exams
Pre-antibiotic era, the Dick test enabled targeted antitoxin use, reducing scarlet fever mortality. Today, vaccination has obsolete it, but understanding remains key for CSIR NET topics in immunology and microbiology. Practice similar MCQs to master susceptibility tests!​