LAUSR

Axial spondyloarthritis (SpA) is an umbrella term encompassing a number of inflammatory conditions involving the axial skeleton. A substantial delay between disease onset, diagnosis and treatment often occurs, related in part to under-recognition of SpA symptoms. Although several studies have investigated since the publication of the ASAS classification criteria in 2009, the prevalence and incidence of axial SpA in the general population and in patients with SpA-related conditions, the actual prevalence of SpA in many countries (including Argentina) is unknown.To estimate the prevalence of axial SpA and the amount of undiagnosed axial SpA in people under 45 years of age that contacted the health care system for chronic low back pain.The setting was a university hospital-based health management organization with a population distribution similary to that of Buenos Aires. All electronic medical records of patients < 45 years of age at the time of onset of symptoms (as per the ASAS 2009 criteria) and chronic low back pain for 3 or more months) seen at the university hospital-based health management organization between 2009 and 2019, were reviewed. If the patient fulfilled the ASAS criteria, was classified as having axial SpA [ankylosing spondylitis (AS) or non-radiographic axial SpA (nr-axSpA)]. Among this group, if the diagnosis was already established in the medical records by the treating physicians, these patients were also classified as diagnosed with axial SpA; if not, they were classified as undiagnosed with axial SpA. We are reporting the results of descriptive analysis.A total of 796 patients were included (Table 1), 426 were women (53.52%, 95% CI 50.1-57) with a median age of 34 years (IQR 29-40) at initiation of low back pain with a median follow up of 77.7 months (IQR 35.7-136.4). The prevalence of axial SpA among patients with chronic low back pain was 5.78% (n= 46, 95% CI 4.2-7.4). 22 patients had AS (2.76%, 95% CI 1.6-3.9) with a median lag time between the onset of low back pain and diagnosis of 58.7 months (IQR 33.5 - 92). All AS cases were already diagnosed. 24 patients had nr-axSpA (3.02%, 95% CI 1.8 - 4.2). Of those, 14 were diagnosed by treating physicians with a lag time median of 23.2 months (IQR 13.1 - 36.5) between the onset of low back pain and diagnosis. Ten patients fulfilled the ASAS criteria (41.7%, CI 95% 22 - 61.4) but were not diagnosed by the treating physicians (22%, 95% CI 9.82-33.66) among the patients with axial SpA.Table 1.Demographic, clinical features and therapeutic characteristics of patients with chroniclow back pain stratified by diagnosisAxial spondyloarthritisN=46Ankylosing spondylitisN=22Diagnosednr-axSpAN=14Undiagnosednr-axSpAN=10OtherdiagnosisN=749Female, n (%, CI)18(39.13%, 25.04-53.23)4(18.18%, 2.06-34.29)10(71.42%,47.76-95.09)4(40%, 9.63-70.36)407(54.34,50.77-57.9)Age at chronic LBP initiation, years, median (IQR)36(29.25-40)32(32-40)38(22-36.75)39(35.25-41.5)34(29-40)Follow up, median months (IQR)88(33.43-148.66)33.67(23.38-90.34)16.73(7.64-24.02)64.77(11.21-164.7)77.69(35.83-135.32)Inflammatory chronic LBP by any criteria n (%)44 (95.7)21 (95.5)13 (92.8)10 (100)56 (7.5, 5.6-9.4)Seen by a Rheumatologist, n (%)42 (91.3)22 (100)14 (100)6 (60)36 (5.1)Lag time between first LBP to SpA diagnosis, months, median (IQR)34.6 (22.6-63.2)58.7 (33.5 – 92)23.1 (13.1-36.5)--bDMARDs treatment n, (%, CI)15(33; 19.5–48)10(45; 24.4–67.8)5(36; 13–64.9)--Lag time between NSAIDs failure and first bDMARDs, months, median (IQR)2.66(2.05-4.63)2.76(2.07-11.3).2.66(2.04-3.25)--CI: 95% confidential interval, IQR: interquartile range, bDMARDs: biologic disease modifying anti-rheumaticdrugs, LBP: low back painIn our cohort, 5.78% of the patients < 45 years with chronic low back pain had axial SpA (AS: 2.76%; and nr-axSpA: 3.02%). Approximately, one in every five patients had undiagnosed axial SpA. Original manuscript made in collaboration with Novartis Argentina S.AMayra Alejandra Tobar Jaramillo: None declared, Nicolas Marin Zucaro: None declared, Javier Rosa: None declared, Josefina Marin: None declared, Maria Laura Acosta Felquer: None declared, LEANDRO FERREYRA: None declared, JOHN FREDY JARAMILLO GALLEGO: None declared, Josefina Marcos Employee of: Novartis, Vanesa Duarte Employee of: Novartis, Enrique Soriano Speakers bureau: AbbVie, Amber, Bristol-Myers Squibb, Eli Lilly, Novartis, Pfizer Inc, Roche, Consultant of: AbbVie, Eli Lilly, GlaxoSmithKline, Novartis, Pfizer Inc, Sandoz, Grant/research support from: AbbVie, Eli Lilly, GlaxoSmithKline, Novartis, Pfizer Inc, Sandoz.