Assessing diagnostic accuracy for asthma with home spirometry in primary care

The aim was to evaluate the diagnostic accuracy of lung function measurements for asthma in primary care, including trial treatment. Undiagnosed patients seeking care for asthma-like symptoms were assessed at primary healthcare centers in Sweden. Participants underwent remote or in-clinic spirometry with bronchodilator responsiveness testing (BDR), remote diurnal variability testing of forced expiratory volume in 1 s (FEV₁) and peak expiratory flow (PEF) over 2-4 weeks using a home spirometry system; and if necessary, three-months trial treatment with inhaled corticosteroids. Overall, 71/123 (58%) were diagnosed with asthma. When comparing patients by asthma diagnosis, sensitivity and specificity for documented diagnosis were 9% (95% CI 3-17) and 100% (93-100) for BDR; 61% (48-72) and 58% (43-71) for FEV₁; and 76% (64-85) and 69% (55-81) for PEF. Diurnal variability testing via home spirometry showed the strongest balance among sensitivity and specificity for asthma.