The use of sputum cell counts to evaluate asthma medications

Corticosteroid resistance in asthma: Cellular and molecular mechanisms

Inhaled glucocorticoids (GCs) are drugs widely used as treatment for asthma patients. They prevent the recruitment and activation of lung immune and inflammatory cells and, moreover, have profound effects on airway structural cells to reverse the effects of disease on airway inflammation. GCs bind to a specific receptor, the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily and modulates pro- and anti-inflammatory gene transcription through a number of distinct and complementary mechanisms. Targets genes include many pro-inflammatory mediators such as chemokines, cytokines, growth factors and their receptors. Inhaled GCs are very effective for most asthma patients with little, if any, systemic side effects depending upon the dose. However, some patients show poor asthma control even after the administration of high doses of topical or even systemic GCs. Several mechanisms relating to inflammation have been considered to be responsible for the onset of the relative GC resistance observed in these patients. In these patients, the side-effect profile of GCs prevent continued use of high doses and new drugs are needed. Targeting the defective pathways associated with GC function in these patients may also reactivate GC responsiveness.

Reproducibility of sputum differential cell counts is not affected by squamous epithelial cells

OBJECTIVE

Induced sputum is used to assess markers of inflammation in asthmatic individuals, and sputum cell differential counts provide an outcome to evaluate the presence, type, and degree of inflammation in the airways. Contamination of sputum slides with squamous epithelial cells (SECs) has been reported to adversely affect the reproducibility of sputum cell differential counts; however, this has not been studied in a controlled manner. Excluding sputum slides because of excessive squamous cell contamination can be problematic resulting in under-powering of studies. The aim of this study is to evaluate the effect of SEC contamination and cell dispersion on the reproducibility of differential counts of sputum cells prepared on glass slides.

STUDY DESIGN

A total of 33 sputum samples were induced from 11 subjects with mild asthma under baseline conditions and following an allergen inhalation challenge. Mucoid and salivary portions of each sample were divided and processed in parallel. To evaluate the effect of increasing the proportion of SEC and to evaluate the effect of increasing the number of leukocytes per high power field (HPF), four slides with varying leukocyte numbers and SEC percentages were prepared from each sample by combining and adjusting the volume of cell suspensions derived from mucous and saliva. The four slides were prepared to fall in the following categories: (A) 50 cells/HPF and <20% SEC; (B) 50 cells/HPF and >20% SEC; (C) 100 cells/HPF and <20% SEC; and (D) 100 cells/HPF and >20% SEC. All slides were blinded and counted twice by an experienced observer, and twice by an inexperienced observer.

RESULTS

The differential cell counts for eosinophils, macrophages, and neutrophils were highly reproducible under all conditions when enumerated by an experienced observer (ICC > 0.9), and furthermore, SEC contamination did not affect ICC when differential counts were enumerated by an inexperienced observer (ICC > 0.8).

CONCLUSION

Our results demonstrate that slides containing SECs, up to 40% in this study, have reproducible differential cell counts.

Introduction to the Canadian Scientific Advisory Committee on Respiratory and Allergy Therapies: in vivo evaluation for clinical testing in COPD and asthma therapy using generics

BACKGROUND

Health Canada posted a guidance for in vivo testing of subsequent market entry (SME) inhaled corticosteroids (ICS) for treatment of asthma and published proceedings regarding SME products for chronic obstructive pulmonary disease (COPD). This manuscript reviews these recommendations and outlines their rationale.

METHODS

The Scientific Advisory Committee on Respiratory and Allergy Therapies (SAC-RAT) met between 2007 and 2009. The committee reviewed approval processes for SME ICS for asthma treatment and a draft guidance was posted by Health Canada. SAC-RAT also reviewed SME long-acting beta agonists (LABA) and fixed drug dose combinations (FDDC) for COPD treatment.

RESULTS

SAC-RAT concluded that measuring airway eosinophils in mild, stable, steroid-naive, subjects was reproducible and measurable. Study duration could be reduced to only 3 weeks using this inflammatory outcome to establish therapeutic equivalence between SME ICS and Canadian reference product. A placebo limb of the trial was added to establish biological activity of the products. The committee recommended that LABA SME products be tested in a clinically stable, representative population with GOLD stage 2 and/or 3 COPD. There was not agreement regarding the extent of allowed FEV(1) reversibility in this population. The FEV(1) area under the curve (AUC) was recommended as a primary endpoint. For equivalence, both AUC and the shape of the curve (assessed by the peak and trough) over a 12-h period should be different from placebo but similar for the SME and reference products. Secondary endpoints were not recommended.

CONCLUSIONS

Clinical presentations of asthma and COPD may overlap but prespecified disease phenotypes can separate the populations. ICS therapeutic equivalence can be assessed by reduction in eosinophil counts tested in steroid naive subjects. Increases in FEV(1) define LABA effects in moderate to severe COPD. When designing trials to assess therapeutic equivalence, the anticipated mechanism of action of the drug should be used to determine outcome measures.

The role of measuring airway hyperresponsiveness and inflammatory biomarkers in asthma

Asthma is characterized by inflammation and airway hyperresponsiveness, which results in episodic airflow obstruction. It is diagnosed once a compatible clinical history plus objective evidence of diurnal variability in peak expiratory flow or significant reversibility to inhaled bronchodilator is documented. In accordance with current guidelines, measures of airway calibre and symptoms allow patients and clinicians to assess the degree of asthma control and titrate pharmacotherapy. However, these parameters fail to reflect the extent of underlying endobronchial inflammation and airway hyperresponsiveness, which in turn suggests that additional measures of asthma control may be of benefit. This evidence-based review highlights ways by which inflammation and airway hyperresponsiveness can be assessed and how they may provide additional useful information in the diagnosis and management of asthmatic patients.

Simplified detection of eosinophils in induced sputum

OBJECTIVE AND DESIGN

The induction of sputum is a safe, noninvasive method of studying airway inflammation in asthma, but the method of analyzing the samples is laborious and requires well-trained technicians using highly specialized laboratory equipment. We introduce a shorter and simpler modification of the process for identifying eosinophilic inflammation from induced sputum (IS) samples.

MATERIAL

Samples of 81 patients referred for IS assessment of respiratory diseases were studied. Four different assessment approaches were studied in comparison with the conventional method of selecting plugs proposed by the European Respiratory Society/American Thoracic Society task force.

RESULTS

One modification of the conventional method of IS processing emerged as simpler to execute and less technologically demanding than the original one (13.0 ± 18.2 vs. 15.4 ± 22.4% eosinophils, P = 0.19).

CONCLUSION

The simpler approach should now encourage the use of IS as a convenient procedure for evaluating eosinophilic inflammation in less sophisticated laboratories.

Revisiting asthma control: how should it best be defined?

Management guidelines for asthma emphasize a stepwise approach in treating this disease based on daytime symptoms, nighttime symptoms, and lung function assessed by peak expiratory flow or forced expiratory volume at 1s (FEV(1)). Although improvement of lung function is a key goal in managing asthma, clinicians often see patients who may have achieved a normal FEV(1) with guideline-recommended treatment but continue to experience limitations in their daily activities. In such situations, focusing the assessment solely on pulmonary function (e.g. FEV(1)) is often inadequate and may lead to undertreatment. Alternate assessment measures are therefore often needed to assess asthma control and achieve a successful treatment outcome. This review will provide practical guidance relevant to the clinical assessment of asthma control.

Step-down compared to fixed-dose treatment with inhaled fluticasone propionate in asthma

BACKGROUND

Inhaled corticosteroids (ICSs) are an effective treatment of asthma even when administered at a low dose. Once asthma is controlled, current guidelines recommend that the dose of ICS be reduced to the lowest possible and effective dose. Although the most appropriate strategy for the stepping down has not yet been defined, quantification of sputum eosinophils and bronchial hyperresponsiveness (BHR) are indeed measures of asthma control.

OBJECTIVE

To compare the efficacy of step-down and fixed-dose strategies in the control of BHR to methacholine and eosinophilic inflammation patients with mild-to-moderate asthma.

METHODS

We performed a double-blind, randomized study to compare inhaled fluticasone propionate (FP), 1,000 microg/d, then reduced to 200 microg/d (group 1; n = 18) to a fixed dose of FP, 200 microg/d (group 2; n = 17) administered for 6 weeks and then 8 weeks in reducing the provocative dose of methacholine causing a 20% fall in FEV1 (PD20) and sputum eosinophils in 35 patients. The duration of the efficacy was also followed subsequently after 8 weeks of placebo treatment.

RESULTS

PD20 remarkably increased with both treatment strategies, but differences between groups were not significant. Sputum eosinophils (median values, percentage) at baseline and after each treatment period were not different (group 1, 16.4 to 1.0 to 2.7%; group 2, 16.7 to 2.8 to 2.8%, respectively). The percentages of patients in whom sputum eosinophilia was normalized (< or = 3%) were as follows: group 1, 69% and 60%; group 2, 50% and 57%. After placebo treatment, sputum eosinophils were still "normalized" in approximately one third of patients.

CONCLUSION

Step-down and fixed-dose strategies with FP improved PD20 and sputum eosinophilia to a similar degree. The effect on sputum eosinophils persisted longer than that on methacholine.

Effects of low dose fluticasone/salmeterol combination on surrogate inflammatory markers in moderate persistent asthma

BACKGROUND

Noninvasive surrogate markers provide valuable information on the asthmatic inflammatory process. We wished to examine the effects of low dose fluticasone/salmeterol combination on different commonly used inflammatory markers in moderate persistent asthma.

METHODS

Twenty-five moderate persistent atopic asthmatics were enrolled of whom 20 completed an open label study. Following an initial 4 week steroid washout period in which patients took salmeterol 50 microg dry powder inhaler 1 puff BD, they received the addition of fluticasone as fluticasone 100 microg/salmeterol 50 microg combination dry powder inhaler 1 puff BD for the next 2 weeks. Exhaled nitric oxide, spirometry, methacholine PD20, sputum/blood eosinophils and sputum/serum eosinophil cationic protein (ECP) were measured following the salmeterol only and fluticasone/salmeterol combination treatment periods.

RESULTS

Compared to salmeterol alone (i.e. after the steroid washout), the use of fluticasone/salmeterol combination conferred significant improvements (P < 0.05) in all surrogate markers of inflammation apart from serum ECP. Geometric mean fold changes were 4.3-fold/1.3-fold for sputum/blood eosinophils, 2.2-fold/1.2-fold for sputum/serum ECP, 2.3-fold for methacholine PD20 and 1.8-fold for exhaled nitric oxide.

CONCLUSIONS

Surrogate markers apart from serum ECP may be used as a guide to evaluate the anti-inflammatory effects of low dose inhaled corticosteroids. Sputum markers tend to be more sensitive than blood when assessing the anti-inflammatory response.