Comparative Sensitivity of Various Indices in Evaluating Improvement in Mild Persistent Asthma

Asthma is traditionally diagnosed and managed based on clinical history and pulmonary function testing however in recent years there has been an effort to develop markers to aid in the diagnosis and management. The fraction of exhaled nitric oxide (eNO) and eosinophil percentage (eos%) in induced sputum are two tests which have been used in clinical practice. We compared these measurements to the concentration of sputum hyaluronan, which is an important pro-inflammatory component of the lung extracellular matrix. Several previous studies have revealed that hyaluronan is increased in lung tissue and sputum of patients with asthma. We enrolled 10 patients with mild, persistent asthma, not using controller medications and measured eNO, sputum eos% and hyaluronan concentration. We compared these markers to the clinical history, asthma control test (ACT) and FEV1% before and after 2-4 weeks of inhaled fluticasone propionate, at 220mcg 2 inhalations bid. There was a significant decrease in the level of eNO (57.3±48.7 vs 17.8±6.7;p= 0.03) and a significant increase in FEV1% (79.6±10.9 vs 85.2±10.5;p=0.02) following the treatment period. Treatment did not produce a significant decrease in mean sputum hyaluronan (240.9±348.3 vs 137.3±131.5;p=0.4), ACT (15.6±5.4 vs 19.1±4.2;p=0.7) or sputum eos% (0.7±1.1 vs 0.1±0.2;p=0.1). In mild, persistent asthmatics there was a significant decrease in eNO and an increase in FEV1% following fluiticasone treatment, however there were no significant differences in ACT score, sputum eos% or hyaluronan. eNo appears to be the most sensitive biomarker for assessing asthma control in patients with mild persistent asthma.