Fast track sputum monitoring in severe asthma

Sputum eosinophil monitoring has become a powerful tool in severe asthma management, due to the role of eosinophils as markers of airway inflammation steroid-responsiveness. However, sputum processing is very time consuming which has impaired its uptake in many clinical settings. Aims: To reduce the time “from expectoration to Differential Cell count” (DCC). We compared 2 different methods of sputum processing to see if a fast track method would yield the same clinical decision outcome for patients. After expectoration, sputum samples were treated with DTT for 15 min following an established protocol (Thorax 1997;52:498–501). Following PBS, filtration and centrifugation, the cell pellet was resuspended in PBS. This cell suspension was then split in two: one half following the regular established protocol with cell viability before cytospinning, the other half diluted until the experienced operator deemed the opacity of the suspension good enough for cytospinning. Both cytospins were then dried (although the air drying time for the fast track sample was reduced), fixed, and stained with Rapid Diff before 400 non-squamous cells were counted. DCC for both methods were compared using Bland-Altman plots. The fast track method yielded a DCC in 60 min, whereas the traditional method took twice as long. Bland-Altman plots of the preliminary results show that the DCC obtained using the fast track method are comparable to those using the traditional method for all cell types. This improved processing time has enabled patients to attend their clinic appointment one hour after their sputum appointment with physicians having reviewed the laboratory results. This has cut repeated visits to the hospital for additional tests.