PT  - JOURNAL ARTICLE
AU  - Sara Muller
AU  - Samantha L Hider
AU  - Karim Raza
AU  - Rebecca J Stack
AU  - Richard A Hayward
AU  - Christian D Mallen
TI  - An algorithm to identify rheumatoid arthritis in primary care: a Clinical Practice Research Datalink study
AID  - 10.1136/bmjopen-2015-009309
DP  - 2015 Dec 01
TA  - BMJ Open
PG  - e009309
VI  - 5
IP  - 12
4099  - http://bmjopen.bmj.com/content/5/12/e009309.short
4100  - http://bmjopen.bmj.com/content/5/12/e009309.full
SO  - BMJ Open2015 Dec 01; 5
AB  - 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: ≥2 RA 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.