Non-invasive methods for monitoring airway inflammation: a comparison of expenditures, gain and clinical value]

Among the noninvasive procedures for the assessment of airway inflammation, the analysis of spontaneous sputum is currently the only method, the expenses of which are covered by health insurance in Germany. It can easily be used for semiquantitive cytological analyses by practising pneumologists. Recent data also indicate the usefulness of sputum induction, particularly in asthma diagnosis and therapy control, and demonstrate its capability of reducing total costs per patient. In contrast to sputum analysis, the measurement of exhaled nitric oxide (NO) yields a read-out without time delay. NO as associated with eosinophils also seems suitable for monitoring airway inflammation. The number of studies regarding NO, both its pathophysiological role and clinical use, is far greater than that regarding any other marker of exhaled air. Measurements are easy and fast, but the costs of analysers are still prohibitive in clinical practice. The analysis of other compounds of exhaled air, particularly those of exhaled breath condensate (EBC), offers fascinating perspectives, owing to the scope of markers that might be measured, and could enable the assessment of multivariate profiles that are useful for diagnosis and therapy control. Currently, however, the method still faces methodological questions, and data indicating its usefulness and cost-efficiency in clinical practice are scarce. Compared to NO, the expenses per measurement in clinical use are mainly due to the costs per marker detection after sampling, as well as storage and transport of samples. The on-site analysis of pH in the EBC could be a first step to circumvent this obstacle.