Definition of index case in English:

index case

(also index patient)

noun

Medicine
  • The first identified case in a group of related cases of a particular communicable or heritable disease.

    • ‘The fifth cluster of infection was the family of the index patient.’
    • ‘Public health departments aren't likely to be the ones diagnosing and identifying an index case of smallpox.’
    • ‘Almost all positive index cases identified through the screening programme were confirmed to have been successfully treated.’
    • ‘Their infection may not be related to the index case, but may reflect the prevalence of the infection in the local community.’
    • ‘There were 72 index cases of tuberculosis, 46 of whom had positive sputum smears for acid-fast bacilli.’
    • ‘The numbers are large because we were unable to identify the index case.’
    • ‘We found no studies comparing index patients given chemoprophylaxis with those who were not.’
    • ‘All participating subjects gave written, informed consent and were interviewed about exposure to the index case and BCG vaccination status.’
    • ‘Four of his family members developed the infection; the brother of the index patient had the earliest date of onset.’
    • ‘Influenza A was confirmed in 510 index patients; 395 (77 percent) of these completed the household contact follow-up protocol.’