Abstract
3 min readBackground Hand pain is common in hand osteoarthritis (OA). Previous cohort studies reported stable average pain levels on the short to midterm. Subgroups with different pain trajectories have been found in knee OA. Similar subgroups of hand OA patients may exist. Knowledge of such subgroups in hand OA patients may help inform decisions for pain treatment. Objectives To determine and characterize subgroups with different hand pain trajectories over four years in hand OA patients. Methods Data from the ongoing HOSTAS (Hand OSTeoArthritis in Secondary care) cohort were used, collected from consecutive patients at the LUMC Rheumatology outpatient clinic with primary hand OA followed for four years. Hand pain measurements were collected annually starting at baseline with the AUSCAN pain questionnaire (range 0-20). Development of pain over time was modelled using latent class growth analysis (LCGA), dividing the cohort into subgroups based on differences in pain development. The optimal model was selected based on the AIC, BIC, entropy and likelihood ratio test for models with n vs n-1 classes. LCGA requires ≥2 measurements per case, so patients with less were excluded. Associations of LCGA classes with baseline demographics and factors associated with hand pain were analyzed using multinomial logistic regression. Results Of 538 participants, 484 completed the AUSCAN at ≥2 timepoints. Data of excluded patients were missing at random. Included and excluded patients were comparable. Of included participants 86% were women, mean (SD) age was 60.8 (8.5), 29% had erosive disease, median (IQR) symptom duration was 5.2 (1.9-12.2), 91% fulfilled the ACR criteria for hand OA. Mean AUSCAN pain score was 9.3 (4.3). LCGA yielded five classes (Figure 1). Classes were characterized by different pain levels at baseline; mean level of pain remained stable over time. Classes with more pain were associated with more erosive disease, higher tender joint count, longer symptom duration, more comorbidities, worse AUSCAN function scores and worse SF-36 and HADS scores (Table 1). Figure 1. LCGA trajectories. Trajectories of AUSCAN pain identified by latent class growth analysis. Least pain to most pain, named class 1 (pink), class 2 (red), class 3 (brown), class 4 (blue) and class 5 (green). Table 1. Multinomial logistic regression for associations with 5 LCGA classes OR (95% CI) Baseline 1 (N=37) 2 (N=104) 3 (N=171) 4 (N=131) 5 (N=41) Erosive disease 1 1.20 (0.45-3.18) 1.48 (0.55-4.03) 1.23 (0.41-3.70) 1.21 (0.30-4.87) Symptom duration, years; 1 1.05 (0.97-1.13) 1.09 (1.01-1.18) 1.13 (1.04-1.22) 1.12 (1.03-1.23) KL sum score 1 1.01 (0.98-1.05) 1.01 (0.98-1.05) 1.02 (0.99-1.06) 1.03 (0.99-1.08) Tender joint count 1 1.17 (0.98-1.39) 1.20 (1.00-1.44) 1.28 (1.07-1.54) 1.29 (1.06-1.57) AUSCAN function 1 0.98 (0.90-1.08) 1.08 (0.99-1.18) 1.17 (1.06-1.30) 1.31 (1.13-1.51) SF-36 -PCS 1 0.95 (0.89-1.02) 0.90 (0.84-0.97) 0.84 (0.77-0.91) 0.81 (0.73-0.89) -MCS 1 0.98 (0.90-1.06) 0.96 (0.89-1.04) 0.95 (0.87-1.03) 0.90 (0.82-0.99) HADS -Depression 1 1.28 (0.91-1.82) 1.46 (1.02-2.09) 1.50 (1.04-2.16) 1.54 (1.04-2.28) -Anxiety 1 1.09 (0.85-1.38) 1.19 (0.93-1.54) 1.19 (0.91-1.54) 1.24 (0.92-1.65) No. Comorbidities 1 1.64 (0.77-3.47) 1.84 (0.86-3.90) 2.22 (1.01-4.88) 2.12 (0.89-5.06) Multinomial logistic regression of variables associated with LCGA classes adjusted for baseline AUSCAN pain, age, sex and BMI. Class 1 = least pain, class 5 = most pain. SF-36 = Short Form-36. MCS = Mental component scale. PCS = Physical component scale. HADS = Hospital anxiety and depression scale. SF-36 scores are standardized on age, sex and nationality with mean 50 and SD 10. Conclusion Latent class growth analysis showed five subgroups with different pain trajectories in hand OA patients, with differing baseline pain and stable pain over time. These subgroups were associated with disease characteristics, number of comorbidities, psychological distress and health-related quality of life. This knowledge can help develop treatment for hand OA patients and inform them about the disease course. Disclosure of Interests: None declared
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