An algorithm to identify rheumatoid arthritis in primary care: a Clinical Practice Research Datalink study

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Müller, S., Hider, S.L., Raza, K., Stack, R.J. ORCID: 0000-0002-0516-0228, Hayward, R.A. and Mallen, C.D., 2015. An algorithm to identify rheumatoid arthritis in primary care: a Clinical Practice Research Datalink study. BMJ Open, 5 (12), e009309. ISSN 2044-6055

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Official URL: http://doi.org/10.1136/bmjopen-2015-009309

Abstract

Objective:
Rheumatoid arthritis (RA) is a multisystem,
inflammatory disorder associated with increased levels
of morbidity and mortality. While much research into
the condition is conducted in the secondary care
setting, routinely collected primary care databases
provide an important source of research data. This
study aimed to update an algorithm to define RA that
was previously developed and validated in the General
Practice Research Database (GPRD).
Methods:
The original algorithm consisted of two criteria. Individuals meeting at least one were considered to have RA. Criterion 1:≥1 RA Read code and a disease modifying antirheumatic drug (DMARD) without an alternative indication. Criterion 2:≥2RA Read codes, with at least one
'strong' code and no alternative diagnoses. Lists of codes for consultations and prescriptions were obtained from the authors of the original algorithm where these were available, or compiled based on the original description and clinical knowledge. 4161 people with a first Read code for RA between 1 January 2010 and 31 December 2012 were
selected from the Clinical Practice Research Datalink
(CPRD, successor to the GPRD), and the criteria applied.
Results:
Code lists were updated for the introduction of new Read codes and biological DMARDs. 3577/
4161 (86%) of people met the updated algorithm for
RA, compared to 61% in the original development
study. 62.8% of people fulfilled both Criterion 1 and
Criterion 2.
Conclusions:
Those wishing to define RA in the CPRD, should consider using this updated algorithm, rather than a single RA code, if they wish to identify only those who are most likely to have RA.