AbstractObjectiveTo summarize evidence on the relationship between early treatment (definition based on symptom/disease duration or radiographic damage) and treatment clinical response in patients with SpA.MethodsA systematic literature review was conducted in studies on SpA patients treated with NSAIDs or biological/targeted synthetic DMARDs addressing the impact of symptom/disease duration or presence of radiographic damage on treatment response assessed by any disease activity outcome. For categorical outcomes, relative risk, relative risk ratio and number needed to treat were calculated, and for continuous outcomes, differences in differences, to compare groups stratified based on symptom/disease duration or the presence of radiographic damage.ResultsFrom the 8769 articles retrieved, 25 were included and 2 added by hand-search, all in axial SpA (axSpA), most of them with low risk of bias. Twenty-one studies compared groups based on symptom duration (n = 6) or disease duration (n = 15) and seven studies based on absence/presence of radiographic damage (two studies used two comparisons). When early axSpA was defined by symptom duration (<5 years) in randomized controlled trials, early treatment was associated with better outcomes in patients with non-radiographic axSpA [n = 2, ASAS40 relative risk ratio 5.24 (95% CI 1.12, 24.41) and 1.52 (0.60, 3.87)] but not in radiographic axSpA (n = 1) [ASAS20 0.96 (0.53–1.73)]. When early axSpA was defined based on disease duration or radiographic damage, no differences were found between groups.ConclusionEvidence towards better outcomes in early axSpA is very limited and restricted to non-radiographic axSpA and <5 years symptom duration. When early axSpA is defined based on disease duration or radiographic damage, no differences in response to treatment are found.