Biomarker-based asthma phenotypes of corticosteroid response

BACKGROUND

Asthma is a heterogeneous disease with different phenotypes. Inhaled corticosteroid (ICS) therapy is a mainstay of treatment for asthma, but the clinical response to ICSs is variable.

OBJECTIVE

We hypothesized that a panel of inflammatory biomarkers (ie, fraction of exhaled nitric oxide [Feno], sputum eosinophil count, and urinary bromotyrosine [BrTyr] level) might predict steroid responsiveness.

METHODS

The original study from which this analysis originates comprised 2 phases: a steroid-naive phase 1 and a 28-day trial of ICSs (phase 2) during which Feno values, sputum eosinophil counts, and urinary BrTyr levels were measured. The response to ICSs was based on clinical improvements, including a 12% or greater increase in FEV1, a 0.5-point or greater decrease in Asthma Control Questionnaire score, and 2 doubling dose or greater increase in provocative concentration of adenosine 5'-monophosphate causing a 20% decrease in FEV1 (PC20AMP). Healthy control subjects were also evaluated in this study for comparison of biomarkers with those seen in asthmatic patients.

RESULTS

Asthmatic patients had higher than normal Feno values, sputum eosinophil counts, and urinary BrTyr levels during the steroid-naive phase and after ICS therapy. After 28-day trial of ICSs, Feno values decreased in 82% of asthmatic patients, sputum eosinophil counts decreased in 60%, and urinary BrTyr levels decreased in 58%. Each of the biomarkers at the steroid-naive phase had utility for predicting steroid responsiveness, but the combination of high Feno values and high urinary BrTyr levels had the best power (13.3-fold, P < .01) to predict a favorable response to ICS therapy. However, the magnitude of the decrease in biomarker levels was unrelated to the magnitude of clinical response to ICS therapy.

CONCLUSION

A noninvasive panel of biomarkers in steroid-naive asthmatic patients predicts clinical responsiveness to ICS therapy.

Predicting steroid responsiveness in patients with asthma using exhaled breath profiling

BACKGROUND

Exhaled breath contains disease-dependent volatile organic compounds (VOCs), which may serve as biomarkers distinguishing clinical phenotypes in asthma. Their measurement may be particularly beneficial in relation to treatment response.

OBJECTIVE

Our aim was to compare the performance of electronic nose (eNose) breath analysis with previously investigated techniques (sputum eosinophils, exhaled nitric oxide (FeNO) and airway hyperresponsiveness) to discriminate asthma from controls and identify steroid responsiveness in steroid-free patients. Trial registration ACTRN12613000038796.

METHODS

Twenty-five patients with mild/moderate asthma had their inhaled steroid treatment discontinued until loss of control or 28 days. They were subsequently treated with oral prednisone 30 mg/day for 14 days. Steroid responsiveness was defined as an increase of either > 12% FEV1 or > 2 doubling doses PC20 AMP. Steroid-free assessment of sputum eosinophils, FeNO and exhaled breath VOCs were used to construct algorithms predicting steroid responsiveness. Performance characteristics were compared by ROC analysis.

RESULTS

The eNose discriminated between asthma and controls (area under the curve = 0.766 ± 0.14; P = 0.002) with similar accuracy to FeNO (0.862 ± 0.12; P < 0.001) and sputum eosinophils (0.814 ± 0.15; P < 0.001). Steroid responsiveness was predicted with greater accuracy by VOC-analysis (AUC = 0.883 ± 0.16; P = 0.008) than FeNO (0.545 ± 0.28; P = 0.751) or sputum eosinophils (0.610 ± 0.29; P = 0.441).

CONCLUSIONS AND CLINICAL RELEVANCE

Breath analysis by eNose can identify asthmatic patients and may be used to predict their response to steroids with greater accuracy than sputum eosinophils or FeNO. This implies a potential role for breath analysis in the tailoring of treatment for asthma patients.

Asthma phenotypes: consistency of classification using induced sputum

BACKGROUND AND OBJECTIVE

Asthma can be classified as eosinophilic or non-eosinophilic based on the cell profile of induced sputum. This classification can help determine whether corticosteroid treatment is indicated. We assessed the stability of these phenotypes over time and with different treatment regimens.

METHODS

Clinically stable, non-smoking, asthmatic adults were enrolled in one of two studies. In study one, induced sputum cell counts from 28 subjects were analysed after 4 weeks without corticosteroid treatment and after 6 week treatments with placebo, regular inhaled beta-agonist, inhaled corticosteroid, and combined beta-agonist and corticosteroid. In study two, sputum from 26 subjects with non-eosinophilic asthma was analysed after 12 weeks of placebo and after four 2-week corticosteroid washouts. Sputum with <2% eosinophils was classified as non-eosinophilic.

RESULTS

Sputum classification changed frequently in both studies. In study one, only one of eight participants with non-eosinophilic sputum after placebo treatment remained non-eosinophilic throughout. In study two, all of participants had at least one eosinophilic sputum sample, despite the fact that all had been non-eosinophilic at recruitment. Neutrophilic asthma was uncommon in both studies and was also inconsistent.

CONCLUSIONS

The phenotypic classification of asthma changes frequently. A diagnosis of non-eosinophilic asthma should not be based on a single sputum sample.

Simvastatin in the treatment of asthma: lack of steroid-sparing effect

BACKGROUND

Statins have anti-inflammatory actions which in theory are potentially beneficial in asthma. Small trials have failed to show a significant benefit, but a systematic study to evaluate the steroid-sparing effect of statin treatment has not been carried out.

METHODS

A randomised, placebo-controlled, crossover trial was conducted of simvastatin 40 mg at night with simultaneous stepwise reduction of fluticasone propionate dose until loss of control occurred, followed by an increase until regain of control ('minimum' dose required) in 51 patients with asthma and sputum eosinophils (steroid-free) ≥ 2%.

RESULTS

43 patients completed the study. There was no significant difference in 'minimum' inhaled corticosteroid (ICS) dose requirement between simvastatin and placebo: (median (IQR) 50 μg daily (0-250) vs 100 μg daily (0-250), p=0.931). 'Minimum' dose distribution was similar (p=0.269). The fluticasone dose at which loss of control occurred did not differ significantly between simvastatin and placebo (p=0.404). In patients with loss of control in both treatment arms, fluticasone dose at loss of control was similar with simvastatin and placebo (median (IQR) 50 μg daily (0-100) for both, p=0.620). In those patients who reached 0 μg/day (n=18), Astma Control Questionnaire (ACQ) was lower (p=0.037), forced expiratory volume in 1 s (FEV(1)) higher (p<0.01) and sputum eosinophils lower with simvastatin compared with placebo (9.5% compared with 25.4%, p=0.033).

CONCLUSIONS

Simvastatin does not have clinically important steroid-sparing effects in patients with eosinophilic asthma. In the absence of steroid, simvastatin is associated with minor improvements in symptoms and lung function, and a reduction in sputum eosinophils. Clinical trial number ACTRN12606000531516.

Long term performance characteristics of an electrochemical nitric oxide analyser

BACKGROUND

The NIOX MINO(®) is a nitric oxide (FE(NO)) analyser based on electrochemical technology. It includes a replaceable sensor. Quality control procedures are recommended, but regular calibration is not possible. We aimed to evaluate the performance characteristics of the NIOX MINO(®) to identify if reproducibility changed over time, or with different sensors. Also, there are reports that reproducibility of FE(NO) may be reduced in patients with high FE(NO): our secondary aim was to address this issue.

METHODS

Reproducibility in 24 separate sensor-analyser units was calculated on three occasions over two months in 17 patients. These included 9 patients whose FE(NO) was high (mean 80 ppb) and 8 in whom FE(NO) was low (mean 16 ppb).

RESULTS

One device failed quality control testing. For the remaining 23 sensor-analyser combinations, the mean coefficient of variation was 4.0% (range 1.2-7.2%) at baseline, 3.6% (range 2.0-7.0) at one month, and 3.6% (range 1.6-7.6%) at two months. The 95% C.I. for the mean limits of agreement for FE(NO) was ± 4.2 ppb (range 0.9-9.6 ppb), ± 3.8 ppb (range 1.6-6.9 ppb) and ± 3.2 ppb (range 1.2-6.8 ppb) respectively (NS). The limits of agreement exceeded the manufacturer's specifications (± 5 ppb) in 0 devices at baseline, 3 (13%) at one month, and 5 (22%) at two months.

CONCLUSIONS

Reproducibility of FE(NO) using the NIOX MINO(®) was within clinically acceptable limits (± 10 ppb) and was generally stable. However, with time, a proportion of individual sensor-analyser combinations yielded variability outside the manufacturer's specifications.

Exercise-induced wheeze: Fraction of exhaled nitric oxide-directed management

BACKGROUND AND OBJECTIVE

Exercise-induced wheeze (EIW) is common. Several treatment options exist. Patients with low fraction of exhaled nitric oxide (F(E)NO) are unlikely to be steroid-responsive and might benefit from non-steroidal therapies. We assessed: the efficacy of cromoglycate, formoterol and montelukast in patients with EIW and low F(E)NO (<35 ppb) in a randomized cross-over trial, and the efficacy of inhaled corticosteroid in a high F(E)NO (>35 ppb) group.

METHODS

Patients had EIW and airway hyperresponsiveness (AHR) to mannitol and/or exercise. Those with low F(E)NO (n = 19) received cromoglycate (20 mg inh. bd + before challenge tests), formoterol (12 microg inh. bd + before challenge tests) and montelukast (10 mg p.o. od), each for 2 weeks. Those with high F(E)NO (n = 20) took inhaled fluticasone (500 microg) daily for 4 weeks. Primary end-points were: 50% reduction in maximum FEV(1) %fall (clinical protection) and decrease in AHR to mannitol.

RESULTS

In patients with low F(E)NO, cromoglycate, formoterol and montelukast significantly decreased AHR to mannitol in 63%, 61% and 47% of patients, respectively. In this group, the magnitude of exercise-induced bronchoconstriction (EIB) was significantly reduced with montelukast and formoterol; between-treatment differences were not significant. Of 6/19 with low F(E)NO and EIB, protection occurred in 67% (cromoglycate), 83% (formoterol) and 50% (montelukast), respectively. In the high F(E)NO group, AHR to mannitol and EIB decreased significantly with fluticasone (P < 0.001, P = 0.005, respectively), and protection occurred in 7/8 (88%) with EIB.

CONCLUSIONS

In patients with EIW and low F(E)NO, the number of 'responders' to cromoglycate, formoterol and montelukast was similar. In a high F(E)NO population the response to inhaled corticosteroid was highly significant and comparable to previous studies.

Effects of steroid therapy on inflammatory cell subtypes in asthma

RATIONALE Airway inflammation in asthma is heterogeneous with different phenotypes. The inflammatory cell phenotype is modified by corticosteroids and smoking. Steroid therapy is beneficial in eosinophilic asthma (EA), but evidence is conflicting regarding non-eosinophilic asthma (NEA). OBJECTIVES To assess the inflammatory cell phenotypes in asthma after eliminating potentially confounding effects; to compare steroid response in EA versus NEA; and to investigate changes in sputum cells with inhaled corticosteroid (ICS). METHODS Subjects undertook ICS withdrawal until loss of control or 28 days. Those with airway hyper-responsiveness (AHR) took inhaled fluticasone 1000 microg daily for 28+ days. Cut-off points were > or = or <2% for sputum eosinophils and > or = or <61% for neutrophils. RESULTS After steroid withdrawal (n=94), 67% of subjects were eosinophilic, 31% paucigranulocytic and 2% mixed; there were no neutrophilic subjects. With ICS (n=88), 39% were eosinophilic, 46% paucigranulocytic, 3% mixed and 5% neutrophilic. Sputum neutrophils increased from 19.3% to 27.7% (p=0.024). The treatment response was greater in EA for symptoms (p<0.001), quality of life (p=0.012), AHR (p=0.036) and exhaled nitric oxide (p=0.007). Lesser but significant changes occurred in NEA (ie, paucigranulocytic asthma). Exhaled nitric oxide was the best predictor of steroid response in NEA for AHR (area under the curve 0.810), with an optimum cut-off point of 33 ppb. CONCLUSIONS After eliminating the effects of ICS and smoking, a neutrophilic phenotype could be identified in patients with moderate stable asthma. ICS use led to phenotype misclassification. Steroid responsiveness was greater in EA, but the absence of eosinophilia did not indicate the absence of a steroid response. In NEA this was best predicted by baseline exhaled nitric oxide.