Induced sputum cell counts: their usefulness in clinical practice

Abstract

Airway inflammation is fundamental to the aetiology and persistence of asthma and other airway conditions. The presence and type of airway inflammation can be difficult to detect clinically, delaying the introduction of appropriate treatment. Induced sputum cell counts are a relatively noninvasive, safe and reliable method of identifying airway inflammation. They can accurately discriminate eosinophilic airway inflammation from noneosinophilic airway inflammation, and help guide therapy. Eosinophilic airway inflammation is steroid responsive whilst noneosinophilic (usually neutrophilic) inflammation generally is not. Macrophages containing haemosiderin can be useful in detecting left ventricular dysfunction and macrophages containing lipid are suggestive of oropharyngeal reflux with microaspiration, both of which can complicate or confuse assessment of airway disease. To date, studies using induced sputum are primarily observational. Management studies based on examination of induced sputum are now needed to validate the clinical utility of this test.

The rise of the phoenix: the expanding role of the eosinophil in health and disease

“…Correlating which compartment is the most relevant for clinical response to therapy will also be important. evaluating asthmatics has now evolved from the research arena to clinical management (89,90).…”

Noninvasive methods to measure airway inflammation: future considerations

“…Regardless of the difficulties to get the costs of measurements reimbursed, a number of centres have already implemented sputum induction into clinical practice. Some of the advantages of this approach have been described in Part I of this series by JAYARAM et al [5]. This paper provides two figures which show in detail how the method of induced sputum can be well incorporated into the diagnostic decision tree for difficult asthma and chronic cough.…”

“…During infections and in patients with COPD, also the total cell count per mL sputum and the proportion of neutrophils can provide relevant information [5]. Owing to their usually low numbers, lymphocytes have seldom been used as a marker, except in patients with sarcoidosis [6].…”

COPD: Eine entzündliche Erkrankung der Atemwege?

“…Da der Anteil dieser Zelltypen im Sputum aber sehr variabel ist, lassen sich selten diagnostische Rückschlüsse ziehen. Eine gleichzeitig deutlich erhöhte Gesamtzellzahl/mL Sputum deutet auf eine infektive Bronchitis hin [26]. Eine Subpopulation von Patienten mit COPD kann jedoch auch vermehrt eosinophile Granulozyten im Sputum aufweisen [27].…”