Background/Purpose: Average delay between symptom onset and diagnosis of ankylosing spondylitis (AS) has been reported as 8–12.8 years^1,2. This study assessed delay in AS diagnosis following diagnosis of back pain (BP), and sought to identify factors affecting time from BP diagnosis to rheumatologist referral in AS patients (pts).

Methods: This longitudinal study used claims data from the large US MarketScan^® commercial insurance claims databases (total number of pts n = 127,137,195 between Jan 2000–Dec 2012). Pts aged 18–64 years with diagnosis of BP in a non-rheumatology setting followed by AS diagnosis in any setting were selected. Pts with a rheumatologist visit on/before AS diagnosis were considered to have been referred. A time-dependent Cox proportional hazard model was used to determine factors associated with referral time after adjusting for age, sex, comorbidities, physician specialty, drug therapy and imaging procedures.

Results: Out of 3,336 pts diagnosed with AS after a diagnosis of BP, 1,244 (37%) were referred to and diagnosed by rheumatologists; remaining were diagnosed in a primary care (PCP; 25.7%), chiropractor/physical therapy (7%), orthopedic (3.8%), pain (3.6%), acute care (3.4%) or other (19.2%) setting. More referred pts were prescribed NSAIDs, DMARDs, corticosteroids and anti-TNF prior to diagnosis of AS, suggesting potentially more severe AS (Table 1). In the time between the diagnoses of BP and AS, 75 (6%) of referred patients were prescribed anti-TNF therapy by rheumatologists and 42 (2%) of non-referred patients were prescribed anti-TNFs by PCPs. Referred pts were also more likely to have had spinal/pelvic imaging procedures (x-ray, MRI, CT scan). Median time from BP diagnosis to rheumatologist referral was 307 days and median time from first rheumatologist visit to AS diagnosis was 28 days. Referred pts were more likely to be younger, male, diagnosed with uveitis, referred by PCPs, prescribed NSAIDs, DMARDs, and anti-TNF prior to referral, and to have had spinal/pelvic x-ray (Table 2).

Conclusion: During 2000–2012, the majority of AS patients who presented with BP were diagnosed without rheumatologist referral. Among those referred, there was a delay of approximately 10 months before a rheumatologist referral was made. After a rheumatologist visit, diagnosis of AS generally followed within a month. Predictors of referral time included young age, male sex, presence of uveitis, use of drug therapy and imaging procedures, and referring physician specialty.

References:

1.      Collantes E et al. Rheumatology 2007;46:1309-15.

2.      Kiltz U et al. Ann Rheum Dis. 2012;71:1207-11.