The different faces of the asthma-COPD overlap syndrome

Early Features of Chronic Obstructive Pulmonary Disease in Patients with Asthma: Is there ACO before ACO?

The diagnosis of asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) is considered when a patient presents features of both asthma and COPD, usually including a component of irreversible airway obstruction (IRAO). However, some patients with asthma, particularly smokers, may have various features typical of COPD in the absence of such component of IRAO. Features of early COPD can be found at a young age in such patients even with normal spirometry. More longitudinal studies should be conducted to determine steps needed to improve clinical outcomes of these patients including the early recognition of these changes and the application of preventative/therapeutic interventions.

Metabolomic fingerprinting and systemic inflammatory profiling of asthma COPD overlap (ACO)

Background

Asthma-COPD overlap (ACO) refers to a group of poorly studied and characterised patients reporting with disease presentations of both asthma and COPD, thereby making both diagnosis and treatment challenging for the clinicians. They exhibit a higher burden in terms of both mortality and morbidity in comparison to patients with only asthma or COPD. The pathophysiology of the disease and its existence as a unique disease entity remains unclear. The present study aims to determine whether ACO has a distinct metabolic and immunological mediator profile in comparison to asthma and COPD.

Methods

Global metabolomic profiling using two different groups of patients [discovery (D) and validation (V)] were conducted. Serum samples obtained from moderate and severe asthma [n = 34(D); n = 32(V)], moderate and severe COPD [n = 30(D); 32(V)], ACO patients [n = 35(D); 40(V)] and healthy controls [n = 33(D)] were characterized using gas chromatography mass spectrometry (GC-MS). Multiplexed analysis of 25 immunological markers (IFN-γ (interferon gamma), TNF-α (tumor necrosis factor alpha), IL-12p70 (interleukin 12p70), IL-2, IL-4, IL-5, IL-13, IL-10, IL-1α, IL-1β, TGF-β (transforming growth factor), IL-6, IL-17E, IL-21, IL-23, eotaxin, GM-CSF (granulocyte macrophage-colony stimulating factor), IFN-α (interferon alpha), IL-18, NGAL (neutrophil gelatinase-associated lipocalin), periostin, TSLP (thymic stromal lymphopoietin), MCP-1 (monocyte chemoattractant protein- 1), YKL-40 (chitinase 3 like 1) and IL-8) was also performed in the discovery cohort.

Results

Eleven metabolites [serine, threonine, ethanolamine, glucose, cholesterol, 2-palmitoylglycerol, stearic acid, lactic acid, linoleic acid, D-mannose and succinic acid] were found to be significantly altered in ACO as compared with asthma and COPD. The levels and expression trends were successfully validated in a fresh cohort of subjects. Thirteen immunological mediators including TNFα, IL-1β, IL-17E, GM-CSF, IL-18, NGAL, IL-5, IL-10, MCP-1, YKL-40, IFN-γ, IL-6 and TGF-β showed distinct expression patterns in ACO. These markers and metabolites exhibited significant correlation with each other and also with lung function parameters.

Conclusions

The energy metabolites, cholesterol and fatty acids correlated significantly with the immunological mediators, suggesting existence of a possible link between the inflammatory status of these patients and impaired metabolism. The present findings could be possibly extended to better define the ACO diagnostic criteria, management and tailoring therapies exclusively for the disease.

The many faces of asthma-chronic obstructive pulmonary disease overlap

PURPOSE OF REVIEW

Asthma and chronic obstructive pulmonary disease (COPD) are common diseases that often overlap. The term asthma-COPD overlap (ACO) has been used to define this entity but there remain several speculations on its exact definition, impact, pathophysiology, clinical features, and management. We reviewed recent publications on ACO to obtain more insight of current knowledge and outline future needs.

RECENT FINDINGS

Criteria for ACO vary from one publication to another and the many variable features of these patients underline the need to reconsider the evaluation and approach of patients with overlapping features based on clinical traits and underlying biological mechanisms. Epidemiological studies reveal that ACO patients have generally an increased burden of illness and healthcare use in addition to poorer quality of life (QoL) compared with asthma and higher or equal to COPD. However, their long-term outcome seems better than patients with COPD alone. Various methods have been proposed to evaluate these patients but their usefulness compared to 'classical' investigation of obstructive lung diseases remains speculative and needs further evaluation. Furthermore, there are no formal studies that examined and compared the different treatment strategies of well-characterized patients with ACO as such patients are usually excluded from clinical trials.

SUMMARY

ACO is a common condition with variable features and a high burden of disease. There is no consensus on its definition, diagnostic, and clinical features and more research should be done on its optimal management and long-term outcomes.

Longitudinal comparison of outcomes in patients with smoking-related asthma-COPD overlap and in non-smoking asthmatics with incomplete reversibility of airway obstruction

Background

There is a need to characterize the impact of the smoking status on the clinical course of asthmatics with incomplete reversibility of airway obstruction (IRAO).

Objective

To compare longitudinal health care use, symptom control, and medication needs between smoking and non-smoking asthmatics with IRAO.

Materials and methods

This was a 12-month follow-up of a cross-sectional study comparing asthmatics with IRAO according to their tobacco exposure. One group had a tobacco exposure ≥20 pack-years and was considered to have asthma-COPD overlap (ACO) and the second with a past tobacco exposure <5 pack-years was considered as non-smokers with IRAO (NS-IRAO). Study participants were contacted by telephone every 3 months to document exacerbation events and symptom control.

Results

A total of 111 patients completed all follow-up telephone calls: 71 ACO and 40 NS-IRAO. The number of exacerbations per patient over the 12-month follow-up was similar in both groups. However, ACO reported worse symptom control throughout the follow-up as compared to NS-IRAO, although no significant variations within a group were observed over the study period.

Conclusion

Although asthma control scores were poorer in ACO patients over 1 year compared to NS-IRAO, exacerbation rate was similar and low in both groups of asthmatics. These observations suggest that poorer asthma control in ACO was not driven by the number of exacerbations but may reflect the influence of chronic airway changes related to the COPD component.

Epidemiology and risk factors of asthma-chronic obstructive pulmonary disease overlap in low- and middle-income countries

BACKGROUND

Asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) represents the confluence of bronchial airway hyperreactivity and chronic airflow limitation and has been described as leading to worse lung function and quality of life than found with either singular disease process.

OBJECTIVE

We aimed to describe the prevalence and risk factors for ACO among adults across 6 low- and middle-income countries (LMICs).

METHODS

We compiled cross-sectional data for 11,923 participants aged 35 to 92 years from 4 population-based studies in 12 settings. We defined COPD as postbronchodilator FEV₁/forced vital capacity ratio below the lower limit of normal, asthma as wheeze or medication use in 12 months or self-reported physician diagnosis, and ACO as having both.

RESULTS

The prevalence of ACO was 3.8% (0% in rural Puno, Peru, to 7.8% in Matlab, Bangladesh). The odds of having ACO were higher with household exposure to biomass fuel smoke (odds ratio [OR], 1.48; 95% CI, 0.98-2.23), smoking tobacco (OR, 1.28 per 10 pack-years; 95% CI, 1.22-1.34), and having primary or less education (OR, 1.35; 95% CI, 1.07-1.70) as compared to nonobstructed nonasthma individuals. ACO was associated with severe obstruction (FEV₁ %, <50; 31.6% of ACO vs 10.9% of COPD alone) and severe spirometric deficits compared with participants with asthma (-1.61 z scores FEV₁; 95% CI, -1.48 to -1.75) or COPD alone (-0.94 z scores; 95% CI, -0.78 to -1.10).

CONCLUSIONS

ACO may be as prevalent and more severe in LMICs than has been reported in high-income settings. Exposure to biomass fuel smoke may be an overlooked risk factor, and we favor diagnostic criteria for ACO that include environmental exposures common to LMICs.

Asthma-chronic obstructive pulmonary disease overlap syndrome: a controversial concept

PURPOSE OF REVIEW

To illustrate the scant evidence and the shortcomings of the concept of 'asthma-COPD overlap syndrome' (ACOS) in terms of clinical utility.

RECENT FINDINGS

Asthma and chronic obstructive pulmonary disease (COPD) are considered as two distinct and heterogeneous diseases. For many years, physicians have been aware that asthma and COPD can coexist in some patients. Recently, the term ACOS has been applied when a person has clinical features of both asthma and COPD. However, the lack of an accurate diagnosis has led to inconsistent data regarding reported prevalence, prognosis and therapeutics. Even today, it has not been possible to establish a phenotypic characterization of ACOS, although it is part of the overall complexity and heterogeneity of COPDs. No high quality data exist on which to base treatment recommendations for ACOS. Consequently, in clinical practice, treatment is extrapolated from the available evidence on asthma and COPD.

SUMMARY

The current concept of ACOS seems clinically irrelevant because it has no influence on the prognosis and treatment of these patients. The authors concluded that the term ACOS should be avoided in the case of patients with features of both asthma and COPD.

Differences between asthma-COPD overlap syndrome and adult-onset asthma

Differences between asthma-COPD overlap syndrome (ACOS) and adult-onset asthma are poorly understood. This study aimed to evaluate these differences in a clinical cohort of patients with adult-onset asthma, as a part of the Seinäjoki Adult Asthma Study (SAAS).188 patients were diagnosed with adult-onset asthma and re-evaluated 12 years after diagnosis. They were divided into three groups based on smoking history and post bronchodilator spirometry values: 1) never- and ex-smokers with <10 smoked pack-years; 2) non-obstructive (forced expiratory volume in 1 s (FEV₁)/forced vital capacity (FVC) ≥0.7) patients with ≥10 pack-years; and 3) ACOS patients with ≥10 pack-years and FEV₁/FVC <0.7.ACOS patients had lower diffusing capacity (D_LCO/V_A 86% predicted versus 98 or 96% predicted; p<0.001), higher blood neutrophil levels (4.50 versus 3.60 or 3.85×10⁹ L^-1; p=0.008), and higher IL-6 levels (2.88 versus 1.52 or 2.10 pg·mL^-1, p<0.001) as compared to never- and ex-smokers with <10 pack-years, or non-obstructive patients with ≥10 pack-years smoking history, respectively. ACOS patients also showed reduced lung function, higher remaining bronchial reversibility and a higher number of comorbidities.This study shows distinct differences in diffusing capacity, blood neutrophil and IL-6 levels, bronchial reversibility, lung function and comorbidities between ACOS and adult-onset asthma. The present findings should be considered in the comprehensive assessment of adult asthma patients.

Concurrent physician-diagnosed asthma and chronic obstructive pulmonary disease: A population study of prevalence, incidence and mortality

OBJECTIVE

We conducted a population-based cohort study to estimate trends in prevalence, incidence, and mortality of concurrent physician-diagnosed asthma and chronic obstructive pulmonary disease (COPD).

STUDY DESIGN AND SETTING

Two validated health administrative case definitions were used to identify asthma and COPD among all individuals aged 35 years and older living in Ontario, Canada. Annual asthma, COPD, and concurrent asthma and COPD prevalence, incidence, and mortality, standardized for age and sex, were estimated, and compared from 2002 to 2012, using generalized linear models.

RESULTS

Standardized prevalence of concurrent asthma and COPD increased by 10.5%, from 2.9% in 2002 to 3.2% in 2012 overall, but more prominently in women compared to men. Overall, standardized incidence decreased by16%, from 2.5 to 2.1 per 1000 individuals, but increased significantly in young adults. All-cause mortality among patients with concurrent asthma and COPD decreased by 11.2%, from 2.6% to 2.2%. Being diagnosed with both diseases was significantly associated with higher all-cause mortality compared to asthma (OR = 1.56, 95% CI: 1.50-1.58), but not compared to COPD (OR = 0.97, 0.96-0.98), except in young adults aged 35 to 49 years where people with asthma and COPD had higher mortality (OR = 1.21, 1.15-1.27).

CONCLUSIONS

In a large North American population, the burden of concurrent physician-diagnosed asthma and COPD is increasing, particularly in women and young adults.

Identifying possible asthma-COPD overlap syndrome in patients with a new diagnosis of COPD in primary care

The asthma-chronic obstructive pulmonary disease (COPD) overlap syndrome (ACOS) remains poorly characterised. Our aim was to describe an algorithm for identifying possible ACOS in adults with newly diagnosed COPD in primary care. General practitioners (n=241) consecutively recruited subjects ⩾35 years, with tobacco exposure, at least one respiratory symptom and no previous diagnosis of obstructive lung disease. Possible ACOS was defined as chronic airflow obstruction, i.e., post-bronchodilator (BD) forced expiratory volume 1/forced vital capacity (FEV₁/FVC) ratio<0.70, combined with wheeze (ACOS wheeze) and/or significant BD reversibility (ACOS BD reversibility). Of 3,875 (50% females, mean age 57 years) subjects screened, 700 (18.1%) were diagnosed with COPD, i.e., symptom(s), tobacco exposure and chronic airflow obstruction. Indications for ACOS were found in 264 (38%) of the COPD patients. The prevalence of ACOS wheeze and ACOS BD reversibility was 27% (n=190) and 16% (n=113), respectively (P<0.001), and only 6% (n=39) of the COPD patients fulfilled both criteria for ACOS. Patients with any ACOS were younger (P=0.04), had more dyspnoea (P<0.001), lower FEV₁%pred (67% vs. 74%; P<0.001) and lower FEV₁/FVC ratio (P=0.001) compared with COPD-only patients. Comparing subjects fulfilling both criteria for ACOS with those fulfilling criteria for ACOS wheeze only (n=151) and those fulfilling criteria for ACOS BD reversibility only (n=74) revealed no significant differences. Irrespective of the applied ACOS definition, no significant difference in life-time tobacco exposure was found between ACOS- and COPD-only patients. In subjects with a new diagnosis of COPD, the prevalence of ACOS is high. When screening for COPD in general practice among patients with no previous diagnosis of obstructive lung disease, patients with possible ACOS may be identified by self-reported wheeze and/or BD reversibility.