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Table 5 Main factors associated with participation in research clinics compared with observed target population.

From: The Knee Clinical Assessment Study – CAS(K). A prospective study of knee pain and knee osteoarthritis in the general population: baseline recruitment and retention at 18 months

  Reported knee pain in last 12 months Attended research clinic OR (95%CI)
N* 3106 819  
Practice    
   A (ref.) 1227 302 1
   B 1251 330 1.10 (0.92, 1.31)
   C 628 187 1.30 (1.05, 1.61)
Age (years):    
   50–59 (ref.) 898 236 1
   60–69 964 312 1.34 (1.10, 1.64)
   70–79 822 222 1.04 (0.84, 1.29)
   80+ 422 49 0.37 (0.26, 0.51)
Gender:    
   Female (ref.) 1832 440 1
   Male 1274 379 1.34 (1.14, 1.57)
Marital status:    
   Married (ref.) 1985 599 1
   Divorced/separated 219 45 0.60 (0.43, 0.84)
   Widowed 705 137 0.56 (0.45, 0.69)
   Single 153 27 0.50 (0.32, 0.76)
Higher education:    
   Yes (ref.) 327 117 1
   No 2685 684 0.61 (0.48, 0.78)
Occupational class†:    
   Non-manual (ref.) 736 301 1
   Manual 1904 420 0.41 (0.34, 0.49)
Baseline HAD Anxiety:    
   None (0–7) (ref.) 1656 500 1
   Possible (8–11) 842 217 0.80 (0.67, 0.97)
   Probable (12+) 508 85 0.46 (0.36, 0.60)
Baseline HAD Depression:    
   None (0–7) (ref.) 2198 663 1
   Possible (8–11) 593 102 0.48 (0.38, 0.61)
   Probable (12+) 221 37 0.47 (0.32, 0.67)
  1. * – individual items may not add to totals due to missing data
  2. † – non-manual consists of higher managerial, higher professional, lower managerial/professional, and intermediate occupations; manual consists of lower supervisory/technical, semi-routine, and routine occupations. Self-employed have been excluded.