Background Disease activity and comorbidity are known to predict functional disability in early inflammatory polyarthritis (IP) in Europe and North America; however predictors in Asian patients are not well described.
Objectives To examine the predictors of functional disability at first presentation in a prospective, multi-ethnic, Asian inception cohort of patients with early IP.
Methods We prospectively recruited all adult patients with inflammatory arthritis affecting ≥2 peripheral joints and symptom onset after September 1, 2012 from the only two hospitals serving Western Singapore. Baseline data on demographics, rheumatoid factor (RF) and anti-citrullinated peptide antibody (ACPA) positivity, body mass index (BMI), smoking status, comorbidity, disease activity score in 28 joints (DAS28) and its components, and physical function (modified Health Assessment Questionnaire, mHAQ) were collected by face to face interview, chart review and assessment by a trained nurse. mHAQ ≥1 was defined as high functional disability. Predictors of high mHAQ were determined by univariate logistic regression and those with p value <0.3 were entered into a multivariable model. Missing values (<1%) were ignored. Results are expressed as odds ratios (OR) and 95% confidence intervals (CI).
Results We recruited 130 patients, of which 112 (86%) had physician-diagnosed rheumatoid arthritis, 14 (11%) had psoriatic arthritis and 4 (3%) had undifferentiated IP. The median (IQR) age was 51.3 (41.0, 59.9) years and 71.5% were women. 61.5% were Chinese, 18.5% Malay and 13.1% were Indian. Median (IQR) disease duration from diagnosis was 3.6 (0, 20.7) weeks and median (IQR) delay from symptom onset to first rheumatologist review was 16.1 (9, 24.7) weeks. 58.5% were positive for RF and/or ACPA. Patients had moderately active disease, with median (IQR) DAS28 at baseline of 4.1 (2.6, 5.4) but low functional disability with median (IQR) mHAQ score of 0.25 (0, 0.75). 20.1% had high functional disability (mHAQ ≥1). Patients with high mHAQ had a shorter delay to first rheumatologist review (median 12.6 vs. 17.6 weeks, p=0.01, Wilcoxon-Mann-Whitney). Polyarticular onset (≥5 joints), high ESR and large joint involvement did not predict high mHAQ independent of DAS28. Age, sex, race, DAS28, BMI and Charlson comorbidity index were significant at p<0.3 on univariate analysis while smoking status and positivity for RF or ACPA were not. On multivariate analysis, only Malay race and DAS28 were independent predictors of mHAQ ≥1 (Figure).
Conclusions Disease activity (DAS28) and Malay race, but not comorbidity were the main predictors of functional disability in this relatively young Asian cohort with low prevalence of comorbidity. High functional disability in Malay patients may suggest immunogenetically more severe disease and should be studied further.
Acknowledgements The Chapter of Rheumatologists, College of Physicians, Academy of Medicine, Singapore.
All patients and rheumatologists at the National University Hospital and Alexandra Hospital (Juronghealth).
Disclosure of Interest None declared
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