Association between asthma control and asthma cost: Results from a longitudinal study in a primary care setting.

Background and objective Asthma control can be assessed with the Asthma Control Test (ACT) and a score of 20 or higher indicates good asthma control. Patients pay for their consultation and treatment in the fee-for-service primary healthcare system in Singapore. We hypothesized that achieving asthma control would result in lower asthma costs through reduced acute exacerbations, fewer physician consultations and lower lost productivity. The study compared the healthcare costs of patients who achieved asthma control and those with suboptimal asthma control based on ACT scores. Factors influencing asthma control and healthcare expenditure over time were also examined. Methods A total of 736 patients were enrolled into an asthma care programme in two polyclinics during 2008 and 2013. Direct costs of asthma management were derived from the frequency of polyclinic consultations, medication costs and hospitalization. Indirect costs were estimated from lost workdays due to exacerbations. The generalized estimating equation (GEE) approach was used to longitudinally model the factors associated with total healthcare expenditure. Results Patients with asthma control spent S$48 (US$36) more per doctor visit on asthma drugs (P < 0.01) but incurred S$65 (US$48) less per doctor visit in total costs (P < 0.01) than those with suboptimal asthma control. The savings from achieving asthma control for obese patients were greater than for normal-weight patients (S$42 or the equivalent of US$31; P < 0.05). Conclusion Optimal asthma control was associated with reduced healthcare costs. An effective treatment regimen should also consider other modifiable factors such as weight control to achieve asthma control and eventually reduce asthma costs.