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Updated: Feb 12, 2026

Comparing Eye-tracking Data of Children with High-functioning ASD, Comorbid ADHD, and of a Control Watching Social Videos
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Comparing Eye-tracking Data of Children with High-functioning ASD, Comorbid ADHD, and of a Control Watching Social Videos

Published on: December 7, 2018

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The Charlson Comorbidity Index in Registry-based Research

Nele Brusselaers, Jesper Lagergren

    Methods of Information in Medicine
    |March 28, 2018
    PubMed

    Insights

    The Charlson Comorbidity Index has many versions, requiring clear reporting for reproducible research. The Royal College of Surgeons

    Area of Science:

    • Medical Informatics
    • Health Services Research
    • Epidemiology

    Background:

    • Comorbidities significantly impact patient survival and prognosis.
    • Comorbidity scores are crucial for assessing prognosis in clinical studies.
    • The Charlson Comorbidity Index (CCI) is widely used, but various adaptations exist with differing International Classification of Diseases (ICD) coding.

    Purpose of the Study:

    • To evaluate the optimal ICD coding for quantifying comorbidity within the Charlson Comorbidity Index.
    • To determine the best coding strategy for registry-based research, especially when using older ICD versions.

    Main Methods:

    • A systematic literature search identified adult CCI adaptations using ICD coding.
    • Back-translation of ICD codes to ICD-8 and ICD-9 was performed using Statistics Sweden's converter.
    • Verification of translated codes against previous CCI versions was conducted.

    Main Results:

    • Sixteen studies reporting ICD adaptations of the CCI were identified.
    • The Royal College of Surgeons (RCS) developed an updated, integrated version suitable for research.
    • The RCS ICD-10 codes were successfully back-translated to ICD-9 and ICD-8 and validated.

    Conclusions:

    • Clear reporting of CCI version, ICD coding, and weighting is essential for research transparency and reproducibility.
    • The RCS version is recommended for registry-based research due to its up-to-date and user-friendly nature, particularly for surgical patients.
    Abstract

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