Page 60 - SPONDYLOARTHRITIS IN COLOMBIA -

Table 4. Association of demographic and SpA disease characteristics that independently prompt to ordering HLA-B27. Results from a multivariable logistic regression model.
Explanatory variables
Male gender (male vs female)
Number of symptoms at presentation (per additional symptom)
Disease duration (per year)
Chronic back pain (yes vs. no) Inflammatory back pain (yes vs. no) Arthritis (yes vs. no)
Enthesitis (yes vs. no)
Uveitis (yes vs. no)
Psoriasis (yes vs. no)
Infection history (yes vs. no)
Diagnostic subtype
HLA-B27 ordered
OR (95% CI) p Value
0.85 (0.53-1.36) 1.45 (1.24-1.71)
1.26 (0.77-2.04) 0.96 (0.53-1.73) 1.14 (0.70-1.85) 1.15 (0.70-1.89) 0.89 (0.58-1.38) 3.19 (0.94-10.87) 0.71 (0.27-1.83) 11.01 (0.61-1.64) 0.85 (0.63-1.15)
0.50
≤0.001
0.34 0.90 0.58 0.55 0.62 0.06 0.48 0.96 0.30
DISCUSSION
The result of this study confirm that rheumatologists working in clinical practice order additional tests such as SI-MRI and HLA-B27 cautiously (not in all patients), and base their diagnostic behaviour on clinical clues. Characteristics associated with the decision to order SI-MRI and/or HLA-B27 in clinical practice, were the presence of IBP, enthesitis, the number of symptoms at presentation and uveitis. Of note, gender, disease duration, the presence of peripheral arthritis and/or psoriasis did not independently determine the behaviour of rheumatologists to request SI-MRI and/or HLA-B27 testing.
Apparently certain clinical manifestations are important. ‘Clinical clues’ make intuitive sense since they may convey the highest probability on a positive test result (either sacroiliitis on MRI or HLA- B27 positivity) and therefore increase efficiency, optimize usage and save costs. This is true especially for AS 21, a disease that has a reportedly strong association with HLA-B27 and is related to the presence of axial manifestations. In contrast, clinicians apparently know that patients presenting with non-inflammatory mechanical back pain, peripheral arthritis or psoriasis for
58