Introduction: Clinical practice guidelines recommend regular adjustment of treatment to achieve control of asthma. A step-up approach based on the degree of disease control should be followed.
Objective: To perform a real-life analysis of the factors that affect the success or failure of this therapeutic strategy and of the criteria applied by clinicians when applying a step-up approach in a representative sample of patients diagnosed with moderate-severe asthma.
Material and Methods: We performed a multicenter retrospective cohort study involving 226 Spanish specialist physicians (98 allergologists, 127 pulmonologists, and 1 family physician). We included 1254 patients (787 women) diagnosed with moderate-severe asthma who underwent step-up therapy during 2016.
Results: Step-up was successful in 44% of cases. The factors associated with success were presence of <2 comorbid conditions, lower grade of severity and therapy step before modification, absence of exacerbations during the previous year, fewer daytime/nighttime symptoms, and limitation in activities, as well as type of inhaled corticosteroid/ long-acting β₂-agonist combination after modification, lower body mass index, and higher fractional exhaled nitric oxide. An early increase in the maintenance dose once a lack of control was detected (≤3 months, >3 to ≤6 months, >6 to ≤12 months) was more likely to be successful.
Conclusion: The factors that determine whether or not this therapeutic strategy manages to control asthma are time since onset of clinical impairment, previous grade of severity, number of comorbid conditions, previous exacerbations, and frequency of symptoms.

Key words: Asthma, Treatment, Step up, Real-life