Impact of Age and Administration Regimens on the Suppressive Effect of Inhaled Glucocorticoids on Eosinophil Markers in Children with Asthma

Blood eosinophils as a marker of likely corticosteroid response in children with preschool wheeze: time for an eosinophil guided clinical trial?

Childhood wheezing is common particularly in children under the age of 6 years and in this age group is generally referred to as preschool wheezing. Particular diagnostic and treatment uncertainties exist in these young children due to the difficulty in obtaining objective evidence of reversible airways narrowing and inflammation. A diagnosis of asthma depends on the presence of relevant clinical signs and symptoms and the demonstration of reversible airways narrowing on lung function testing, which is difficult to perform in young children. Few treatments are available and inhaled corticosteroids are the recommended preventer treatment in most international asthma guidelines. There is, however, considerable controversy about its effectiveness in children with preschool wheeze and a corticosteroid responder phenotype has not been established. These diagnostic and treatment uncertainties in conjunction with the knowledge of corticosteroid side effects, in particular the reduction of growth velocity, have resulted in a variable approach to inhaled corticosteroid prescribing by medical practitioners and a reluctance in carers to regularly administer the treatment. Identifying children who are likely responders to corticosteroid therapy would be a major benefit in the management of this condition. Eosinophils have emerged as a promising biomarker of corticosteroid responsive airways disease, and evaluation of this biomarker in sputum has successfully been employed to direct management in adults with asthma. Obtaining sputum from young children is time consuming and difficult, and it is hard to justify more invasive procedures such as a bronchoscopy in young children routinely. Recently, in children, interest has shifted to assessing the value of less invasive biomarkers of likely corticosteroid response and the biomarker 'blood eosinophils' has emerged as an attractive candidate. The aim of this review was to summarize the evidence for blood eosinophils as a predictive biomarker for corticosteroid responsive disease with a particular focus on the difficult area of preschool wheeze.

Saliva and serum eosinophil cationic protein in asthmatic children and adolescents with and without allergic sensitization

Saliva eosinophil cationic protein (ECP) is higher in asthmatic adults than in healthy ones. However, its relationship with asthma severity, other atopic conditions and allergic sensitization have not been reported. Saliva collection is painless, readily acceptable to children and parents, and can be a potentially useful body fluid to measure asthma biomarkers. We recruited 102 physician-diagnosed young asthmatic subjects from outpatient clinics with change in FEV(1) > or = 12% with inhaled salbutamol and collected data on asthma severity, concurrent allergic rhinitis (AR) and atopic dermatitis (AD), and medication used (bronchodilator and corticosteroid). We measured whole saliva and serum ECP and performed skin prick tests (SPT) for three dust mites (Dermatophagoides pteronyssisinus, Dermatophagoides farinae and Blomia tropicalis) and two cockroaches (Periplaneta americana and Blatella germanica). Median salivary ECP was 84.6 microg/l (inter-quartile range [IQR]: 40.9-147.9) and median serum ECP was 14.7 microg/l (IQR: 6.4-32.1). Serum ECP was only higher in children whose sleep was disturbed by asthma in the past year than those who were not (geometric mean [GM]: 18.9 vs. 11.1 microg/l, relative mean difference [RMD]: 1.71 [95%CI: 1.09-2.69]). Serum ECP was increased among asthmatic children on inhaled corticosteroid than those not using them (GM: 15.6 vs. 8.1 microg/l, RMD: 1.93 [95%CI: 1.11-3.39]). Salivary ECP was not associated with asthma severity, concurrence of atopic conditions, medications used, or any SPT parameter. Saliva ECP did not correlate with serum ECP (r(s) = 0.032, p = 0.790). Salivary and serum ECP did not correlate with wheal size for any skin prick test.

Eosinophil cationic protein: is it useful in asthma? A systematic review

INTRODUCTION

Eosinophil cationic protein (ECP) has been widely investigated as a potential biomarker of airway inflammation.

METHOD

A systematic review was performed using Medline with key terms eosinophil cationic protein and asthma, limiting the search to titles or abstracts. Out of 688 potential papers found, abstracts were reviewed based on the following criteria: (1) ECP was used as a biological marker, (2) asthma was the index disease studied, (3) it was a controlled clinical study and (4) ECP was assessed as a diagnostic, assessment or management tool. One hundred and sixty-nine articles satisfied the selection criteria and their full-text versions were reviewed. Only 53 papers were found to provide clinically useful information.

RESULTS

ECP has been measured in serum, plasma, sputum, saliva and broncho-alveolar lavage fluids but serum and sputum are the most established. Levels of ECP in normal and asthmatic subjects in various body fluids were identified. ECP correlates well with airway inflammation but not airway hyper-responsiveness. It is raised in other atopic diseases and hence is not diagnostic for asthma. However, it has been shown to be useful in assessing asthma severity, compliance with anti-inflammatory asthma therapy and as a guide to tailing down inhaled corticosteroid therapy. Although there is some evidence that ECP levels are affected by age, smoking, circadian rhythm and seasonal variation, only smoking appears to be of clinical significance.

DISCUSSION

Despite its limitations, ECP remains potentially useful in asthma management. Future research on ECP should focus on using serial measurements and combining it with other markers of asthma which may increase its clinical usefulness.