Background/Purpose: Back pain exerts significant economic burden and in its inflammatory form is the main clinical symptom of axial spondylarthritis. We evaluated differences in patient history between males and females presenting with back pain. We also evaluated the association between sex and axial spondylarthritis (axSpA).

Methods: A retrospective study was conducted in adult (age 21 & up) members belonging to Kaiser Permanente Southern California health plan. Between 01/2009-12/2013, we included patients who presented with either a diagnosis or chief compliant of back pain during a face-to-face encounter with a provider. Patients were followed until 12/2020 to see if they subsequently developed axSpA. We evaluated differences between male and female patient’s history (in the 3 years prior to back-pain diagnosis) of: pain medication use (non-steroidal anti-inflammatory drugs (NSAIDs), opioid drugs, non-opioid drugs, corticosteroids, biologic and synthetic disease-modifying antirheumatic drugs (DMARDs)); imaging tests (X-ray, computed tomography, magnetic resonance imaging, ultrasound etc.); and laboratory tests for inflammation (erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP)). Differences between sex in patient history were evaluated by multivariable logistic regression model adjusting for socio-demographic factors (age, race, ethnicity, insurance type, education, and income), modifiable risk factors (smoking status and obesity) and prevalence of Elixhauser comorbidity conditions. A proportional hazards model adjusting for socio-demographic factors, modifiable risk factors and comorbid conditions was used to evaluate the association between sex and axSpA. Loss to follow-up due to death or health plan disenrollment was right censored in the proportional hazards model.

Results: The sample (N= 107,598) was predominantly made up of females (52%). The majority (36%) age category was 21-45 years, while the majority (45%) of patients had 2 or more Elixhauser comorbidity conditions. Female sex was associated with significantly (all P< 0.001) higher odds of history of pain medication use [NSAIDs (odds ratio (OR) 1.40 (95% CI 1.36-1.44)), opioids (OR 1.25 (1.22-1.29)), non-opioids (OR 1.49 (1.38-1.60)), corticosteroids (OR 1.11 (1.07-1.15)) and synthetic DMARDs (OR 1.65 (1.48-1.83))]. Female sex was also associated with nearly 4-fold higher odds of history of imaging test orders (OR 3.81 (3.68-3.93)) and 38% higher odds of history of inflammation detection laboratory test orders (OR 1.38 (1.34-1.42)). Lastly, female sex was associated with 36% higher hazard of future axSpA diagnosis (hazard ratio 1.36 (1.20 -1.54))).

Conclusion: In this retrospective study, female sex was found to be disproportionately associated with higher odds of pain medication use, history of imaging tests and laboratory tests for inflammation, observed prior to back pain. We also observed higher hazard of future axSpA diagnosis in females presenting with back pain. More studies are needed to better understand the natural history of back pain and if it predominantly relates to non-radiographic axSpA in females.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/differences-between-male-vs-female-presenting-with-back-pain-in-an-integrated-delivery-system/