Comparison of two referral strategies for diagnosis of axial spondyloarthritis: the Recognising and Diagnosing Ankylosing Spondylitis Reliably (RADAR) study.
OBJECTIVE
To determine which of two referral strategies, when used by referring physicians for patients with chronic back pain (CBP), is superior for diagnosing axial spondyloarthritis (SpA) by rheumatologists across several countries.


METHODS
Primary care referral sites in 16 countries were randomised (1 : 1) to refer patients with CBP lasting >3 months and onset before age 45 years to a rheumatologist using either strategy 1 (any of inflammatory back pain (IBP), HLA-B27 or sacroiliitis on imaging) or strategy 2 (two of the following: IBP, HLA-B27, sacroiliitis, family history of axial SpA, good response to non-steroidal anti-inflammatory drugs, extra-articular manifestations). The rheumatologist established the diagnosis. The primary analysis compared the proportion of patients diagnosed with definite axial SpA by referral strategy.


RESULTS
Patients (N=1072) were referred by 278 sites to 64 rheumatologists: 504 patients by strategy 1 and 568 patients by strategy 2. Axial SpA was diagnosed in 35.6% and 39.8% of patients referred by these respective strategies (between-group difference 4.40%; 95% CI -7.09% to 15.89%; p=0.447). IBP was the most frequently used referral criterion (94.7% of cases), showing high concordance (85.4%) with rheumatologists' assessments, and having sensitivity and a negative predictive value of >85% but a positive predictive value and specificity of <50%. Combining IBP with other criteria (eg, sacroiliitis, HLA-B27) increased the likelihood for diagnosing axial SpA.


CONCLUSIONS
A referral strategy based on three criteria leads to a diagnosis of axial SpA in approximately 35% of patients with CBP and is applicable across countries and geographical locales with presumably different levels of expertise in axial SpA.
Medical Department I, Rheumatology, Charite Campus Benjamin Franklin, Berlin, Germany. joachim.sieper@charite.de
Joachim
J
Sieper
Shankar
S
Srinivasan
Omid
O
Zamani
Herman
H
Mielants
Denis
D
Choquette
Karel
K
Pavelka
Anne Gitte
AG
Loft
Pál
P
Géher
Debashish
D
Danda
Tatiana
T
Reitblat
Fabrizio
F
Cantini
Codrina
C
Ancuta
Shandor
S
Erdes
Helena
H
Raffayová
Andrew
A
Keat
J S H
JS
Gaston
Sonja
S
Praprotnik
Nathan
N
Vastesaeger
D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D001416:Back Pain / Q000209:etiology; D059350:Chronic Pain / Q000209:etiology; D005260:Female; D020022:Genetic Predisposition to Disease; D015796:HLA-B27 Antigen / Q000032:analysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011320:Primary Health Care / Q000458:organization & administration; D012017:Referral and Consultation / Q000458:organization & administration*; D058566:Sacroiliitis / Q000209:etiology; D025241:Spondylarthritis / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy / Q000235:genetics
D000894:Anti-Inflammatory Agents, Non-Steroidal; D015796:HLA-B27 Antigen