Table 3 

Multinomial regression function: 'any OA' 

N 
666 

Missing 
49 



NONE 
ISOPF 
COMB 

n = 212 
n = 170 
n = 284 

aOR (95% CI)* 
aOR (95% CI)* 



Age (per year) 
0.96 (0.93, 0.99) 
1 
1.04 (1.01, 1.07) 
Female gender 
2.87 (1.79, 4.59) 
1 
1.56 (0.99, 2.47) 
BMI (per kg/m^{2}) 
0.94 (0.89, 0.99) 
1 
1.04 (0.99, 1.09) 
Whole leg pain 
2.12 (1.10, 4.08) 
1 
0.74 (0.37, 1.50) 
Difficulty descending stairs 
0.45 (0.27, 0.73) 
1 
1.15 (0.74, 1.80) 
Intercondylar gap > 0 cm 
1.38 (0.75, 2.57) 
1 
2.34 (1.32, 4.14) 
Knee effusion† 
0.82 (0.49, 1.35) 
1 
2.42 (1.55, 3.77) 
Fixed flexion deformity 
0.20 (0.04, 0.93) 
1 
2.31 (1.13, 4.77) 
Coarse crepitus‡ 
0.64 (0.40, 1.02) 
1 
1.57 (1.03, 2.41) 
Knee flexion ROM (per degree) 
0.99 (0.96, 1.01) 
1 
0.96 (0.94, 0.98) 


Nagelkerke's Pseudo R^{2} 
0.41 

Pearson goodnessoffit 
P = 0.45 

Pretest probability 
0.32 
0.26 
0.43 


Correctly classified on 'balance of probabilities' 
136 (64%) 
36 (21%) 
220 (77%) 
Correctly classified on 'confident diagnosis' (probability ≥0.8) 
18 (8%) 
0 
79 (28%) 


* odds ratio with 95% confidence interval, adjusted for all other covariates in model. aOR is interpreted as the odds relative to the ISOPF group (for example, compared to those people with ISOPF, people with COMB have 2.4 times the odds of having knee effusion; compared with ISOPF, those with no ROA have 0.45 times the odds of difficulty descending stairs, that is, lower risk). †Mild/Moderate/Gross ‡Possible/definite 

Peat et al. Arthritis Research & Therapy 2012 14:R63 doi:10.1186/ar3779 