ObjectivesTo evaluate the burden of residual disease in patients with axial spondyloarthritis (axSpA) or psoriatic arthritis (PsA) who achieved low disease activity (LDA) status.MethodsWe used baseline data from a clinic registry of SpA in a tertiary hospital in Singapore. For axSpA, LDA was defined as Ankylosing Spondylitis (AS) Disease Activity Score based on erythrocyte sedimentation rate (ASDAS-ESR) < 2.1 or Bath AS Disease Activity Index (BASDAI) < 3/10. For PsA, LDA was defined by achieving 5/7 cutoffs in the minimal disease activity (MDA) or Clinical Disease Activity Index for Psoriatic Arthritis (cDAPSA) ≤ 13.ResultsIn 262 cases of axSpA (21% women; mean ± standard deviation (SD) age 42 ± 14 yrs), 33% and 43% of patients achieved ASDAS-ESR and BASDAI LDA states, respectively, while in 142 cases of PsA (49% women, mean age 51 ± SD 14 yrs), 35% and 63% achieved MDA and cDAPSA LDA, respectively. Both axSpA and PsA patients with LDA had pain scores ranging from 14.0 to 21.4/100 and fatigue scores ranging from 3.1 to 3.6/10. Substantial burden in physical disability and mental well-being were observed, with low physical and mental component summary scores on the 36-item Short Form Health Survey. AxSpa patients in BASDAI LDA had higher ESR and lower disability than those in ASDAS-ESR LDA. cDAPSA classified nearly twice as many PsA patients into LDA than MDA. Compared to PsA patients in MDA LDA, those in cDAPSA LDA had higher active joint counts, dactylitis, enthesitis, pain scores, and patient global assessment.ConclusionDespite being in LDA, patients with axSpA and PsA experienced substantial residual burden in pain, poorer physical function, and mental well-being.