Frequent exacerbators--a distinct phenotype of severe asthma

BACKGROUND

Exacerbations represent a major source of morbidity and mortality in asthma and are a prominent feature of poorly controlled, difficult-to-treat disease.

OBJECTIVE

The goal of our study was to provide a detailed characterization of the frequent exacerbator phenotype and to identify risk factors associated with frequent and seasonal exacerbations.

METHODS

Ninety-three severe asthmatics (SA) and 76 mild-to-moderate patients (MA) were screened and prospectively followed up for 1 year (NCT00555607). Medical history, baseline clinical data and biomarkers were used to assess risk factors for frequent exacerbations.

RESULTS

During the study, 104 exacerbations were recorded in the SA group and 18 in the MA. Frequent exacerbators were characterized by use of higher doses of inhaled (1700 vs. 800 μg) and oral (6.7 vs. 1.7 mg) glucocorticosteroids, worse asthma control (ACQ score 2.3 vs. 1.4), lower quality of life (SGRQ score 48.5 vs. 33.3), higher sputum eosinophils (25.7% vs. 8.2%) and a more rapid decline in FEV1 /FVC ratio (-0.07 vs. -0.01 ΔFEV1 /FVC, frequent vs. non-frequent, respectively, P < 0.05). Exhaled NO > 45 p.p.b. and a history of smoking were associated with an increased risk of frequent exacerbations (odds ratios: 4.32 and 2.90 respectively).

CONCLUSION AND CLINICAL RELEVANCE

We were able to distinguish and characterize a subphenotype of asthma subjects--frequent exacerbators--who are significantly more prone to exacerbations. Patients with FeNO > 45 p.p.b. and a history of smoking are at increased risk of frequent exacerbations and require careful monitoring in clinical practice.

Three phenotypes of adult-onset asthma

RATIONALE

Adult-onset asthma differs from childhood-onset asthma in many respects. It is more heterogeneous, often severe and frequently associated with loss of lung function. To identify underlying mechanisms of adult-onset asthma and to capture predictors of disease progression, detailed characterization and phenotyping is necessary.

OBJECTIVES

To characterize adult-onset asthma and identify subphenotypes of adult-onset asthma.

METHODS

A cohort of 200 patients with adult-onset (>18 year) asthma (age 54 (26-75) year) was recruited from one academic and three nonacademic pulmonary outpatient clinics in Amsterdam, the Netherlands. These patients were fully characterized with respect to clinical, functional and inflammatory markers. After data reduction, K-means nonhierarchical cluster analysis was performed to identify clusters of adult-onset asthma.

MEASUREMENTS AND MAIN RESULTS

Patients with adult-onset asthma were predominately female (61%) and nonatopic (55%). Within this group of patients were identified three clusters of adult-onset asthma. Cluster 1 (n = 69) consisted of patients with severe eosinophilic inflammation-predominant asthma and persistent airflow limitation despite high-intensity anti-inflammatory treatment, with relatively low symptom scores. The second cluster was characterized by obese women with frequent symptoms, high healthcare utilization and low sputum eosinophils. The third cluster consisted of patients with mild-to-moderate, well-controlled asthma with normal lung function and low inflammatory markers. Repeatability accuracy was 98.2%.

CONCLUSIONS

Amongst patients with adult-onset asthma, three subphenotypes can be identified with distinct clinical and inflammatory characteristics. These subphenotypes help to understand the underlying pathobiology and provide clinicians with directions for personalized management.

Deep sequencing of antiviral T-cell responses to HCMV and EBV in humans reveals a stable repertoire that is maintained for many years

CD8⁺ T-cell responses against latent viruses can cover considerable portions of the CD8⁺ T-cell compartment for many decades, yet their initiation and maintenance remains poorly characterized in humans. A key question is whether the clonal repertoire that is raised during the initial antiviral response can be maintained over these long periods. To investigate this we combined next-generation sequencing of the T-cell receptor repertoire with tetramer-sorting to identify, quantify and longitudinally follow virus-specific clones within the CD8⁺ T-cell compartment. Using this approach we studied primary infections of human cytomegalovirus (hCMV) and Epstein Barr virus (EBV) in renal transplant recipients. For both viruses we found that nearly all virus-specific CD8⁺ T-cell clones that appeared during the early phase of infection were maintained at high frequencies during the 5-year follow-up and hardly any new anti-viral clones appeared. Both in transplant recipients and in healthy carriers the clones specific for these latent viruses were highly dominant within the CD8⁺ T-cell receptor Vβ repertoire. These findings suggest that the initial antiviral response in humans is maintained in a stable fashion without signs of contraction or changes of the clonal repertoire.

Several viruses have found ways to evade the human immune system and cause latent infections. Examples include HIV and herpes-viruses. Most humans carry these herpes-viruses. The human immune system mounts continuous responses against these viruses to prevent them from causing disease. If this balance is disturbed, these viruses can cause extensive pathology. We do not know how the immune response against these viruses evolves over time. Understanding this response might help to understand why the immune system does not clear these viruses and might help in preventive and therapeutic strategies. Here we used a new technology that allowed us to track virus specific immune cells (CD8⁺ T cells) over time in a quantitative manner. When we used this technology to study the evolution of latent responses against herpes-viruses (from infection until 5 years later) we found that immune responses were very rigid and did not evolve over time. Collectively our data shows that – for these herpes-viruses – the initial immune response is maintained despite the fact that this does not result in clearance of the virus. Therefore, if a virus survives the initial response, it will not be cleared in the future. This is an important consideration in understanding latent infection and for vaccination-design.

Non-atopic males with adult onset asthma are at risk of persistent airflow limitation

BACKGROUND

Patients with asthma have on average a more rapid decline in FEV (1) as compared with the general population. Recent cluster analysis has revealed different asthma phenotypes that can be distinguished by age of onset and reversibility of airflow limitation.

OBJECTIVE

This study aimed at detecting risk factors associated with persistent airflow limitation in patients with the adult onset asthma phenotype.

METHODS

We recruited 88 patients with adult onset (≥ 18 years) asthma from an academic pulmonary outpatient clinic in the Netherlands. The associations of age, age of asthma onset, asthma duration, gender, race, atopy, smoking pack-years, BMI, use of oral corticosteroids with post-bronchodilator FEV (1) /FVC were investigated.

RESULTS

Multiple linear regression analysis showed an association of absence of atopy (r = -0.27, B = -0.26, P = 0.01) and male gender (r = 0.31, B = 0.30, P = 0.004) with post-bronchodilator FEV (1) /FVC. Multiple logistic regression analysis showed that male patients were 10.8 (CI: 2.6-45.2) times the odds than women to have an FEV (1) /FVC < 0.7, and non-atopic patients were 5.2 (CI: 1.3-20.3) times the odds to have an FEV (1) /FVC < 0.7 than atopic patients.

CONCLUSIONS AND CLINICAL RELEVANCE

We conclude that in patients with adult onset asthma, male gender and absence of atopy are associated with persistent airflow limitation. This might suggest that amongst patients with adult onset asthma, non-atopic male patients are at increased risk of accelerated decline in lung function.

Deficient alpha-1-antitrypsin phenotypes and persistent airflow limitation in severe asthma

BACKGROUND

Persistent airflow limitation is common among patients with severe asthma, but its pathogenesis has not been fully clarified. Severe alpha-1-antitrypsin (AAT) deficiency is a risk factor of chronic airflow limitation and emphysema, and partially deficient phenotypes have been associated with an accelerated decline in lung function. We hypothesized that partial deficiency of AAT (non-PiM AAT phenotype) is a risk factor of persistent airflow limitation in asthma.

METHODS

In 122 patients with severe asthma (86 females; age (median (range)): 44.0 yr (18-75)) postbronchodilator FEV1 and FEV1/VC were measured and the AAT phenotype was determined. Persistent airflow limitation was defined as postbronchodilator FEV1 or FEV1/VC < 75% pred. with TLC > 75% pred.

RESULTS

Six patients (4.9%) had a non-PiM phenotype (1 MF, 3 MS, 1 MZ and 1 SZ). Of the 58 patients with persistent airflow limitation only 1 patient (1.7%) had a non-PiM phenotype vs. 7.8% among the patients without persistent airflow limitation (P = 0.21). Postbronchodilator FEV1/VC (% pred.) was higher in the non-PiM patients than in the PiM patients (P = 0.02), the other lung function parameters were not different. Linear regression analysis showed no association between AAT phenotype and FEV1% predicted (P = 0.26).

CONCLUSIONS

AAT heterozygoty does not seem to be an important risk factor of persistent airflow limitation in patients with asthma. Although confirmation by longitudinal follow-up studies with larger sample sizes is needed, these results suggest that routine assessment of the AAT phenotype is not indicated in asthmatic patients even if they exhibit fixed airflow limitation.

Risk factors of frequent exacerbations in difficult-to-treat asthma

Recurrent exacerbations are a major cause of morbidity and medical expenditure in patients with asthma. Various exogenous and endogenous factors are thought to influence the level of asthma control, but systematical data on the involvement of these factors in the recurrence of asthma exacerbations are scarce. In this study, 13 clinical and environmental factors potentially associated with recurrent exacerbations were investigated in 136 patients with difficult-to-treat asthma. Patients with more than three severe exacerbations (n = 39) in the previous year were compared with those with only one exacerbation per year (n = 24). A systematic diagnostic protocol was used to assess 13 potential risk factors. Factors significantly associated with frequent exacerbations included: severe nasal sinus disease (adjusted odds ratio (OR) 3.7); gastro-oesophageal reflux (OR 4.9); recurrent respiratory infections (OR 6.9); psychological dysfunctioning (OR 10.8); and obstructive sleep apnoea (OR 3.4). Severe chronic sinus disease and psychological dysfunctioning were the only independently associated factors (adjusted OR 5.5 and 11.7, respectively). All patients with frequent exacerbations exhibited at least one of these five factors, whilst 52% showed three or more factors. In conclusion, the results show that recurrent exacerbations in asthma are associated with specific co-morbid factors that are easy to detect and that are treatable. Therapeutic interventions aimed at correcting these factors are likely to reduce morbidity and medical expenditure in these patients.

Factors associated with persistent airflow limitation in severe asthma

Persistent airflow limitation can develop in nonsmoking patients with asthma. However, the prevalence and risk factors for airways obstruction with incomplete reversibility in asthma are unknown. We assessed the prevalence of persistent airflow limitation (defined as postbronchodilator FEV(1) or FEV(1)/VC < 75% predicted) in 132 nonsmoking outpatients with severe asthma visiting chest physicians in general hospitals in The Netherlands. They had used inhaled corticosteroids (> or = 1,600 microg/d) and/or daily oral prednisone and long-acting bronchodilators for > 1 yr. In addition, we examined whether persistent airways obstruction in these patients was associated with specific clinical characteristics (age at onset, smoking history, atopic status, bronchodilator reversibility, provocative concentration of histamine causing a 20% decrease in FEV(1) [PC(20)histamine]) or markers of inflammation (exhaled nitric oxide [NO], blood eosinophils, total IgE; and eosinophilia or neutrophilia in induced sputum). Multiple logistic regression analyses were used to calculate adjusted odds ratios (OR). Persistent airflow limitation was observed in 49% of the patients in the study, and apart from older age and longer asthma duration, was strongly associated with a sputum eosinophils percent > or = 2% (OR = 7.7; confidence interval [CI]: 2.4 to 25), PC(20)histamine < or = 1.0 mg/ml (OR = 3.9; CI: 1.2 to 13), and adult onset (> or = 18 yr) of asthma (OR = 3.3; CI: 1.2 to 9). Only sputum eosinophilia appeared to be independently associated with persistent airflow limitation (OR = 8.9; CI: 1.3 to 59). In conclusion, persistent airflow limitation is common in adult patients with severe asthma, and is associated with adult onset of the disease, airway hyperresponsiveness, and most importantly, sputum eosinophilia. These findings suggest that eosinophilic airway inflammation contributes to persistent airflow limitation in severe asthma. Whether reduction of sputum eosinophils with more vigorous treatment leads to a better prognosis in severe asthma is still an open question.

Sputum induction in severe asthma by a standardized protocol: predictors of excessive bronchoconstriction

Sputum induction is a noninvasive method to evaluate airway inflammation. We investigated whether it can be safely and successfully performed in patients with severe, difficult-to-control asthma, and whether the patients at risk can be identified. Ninety-three severe asthmatics were included, all symptomatic despite inhaled corticosteroids (> or = 1,600 microg/d) and long-acting beta(2)-agonists > 1 yr. Patients with a postbronchodilator FEV(1) < 1 L and < 50% predicted were excluded from participation. Sputum induction was performed according to a strict protocol, using 0.9%, 3.0%, and 4.5% NaCl inhalation. In 74% (CI: 64 to 83%) of patients an adequate sputum sample could be obtained. Twenty-two percent (CI: 14 to 33%) developed excessive bronchoconstriction (decrease in FEV(1) > 15% from baseline) despite the continuing use of long-acting bronchodilators and pretreatment with 400 microg salbutamol. The decrease in FEV(1) was associated with increased use of rescue short-acting beta(2)-agonists in the previous 2 d (r(s) = 0.51, p = 0.002), lower postbronchodilator FEV(1) (r(s) = -0.31, p = 0.004), and lower provocative concentration of histamine causing a 20% reduction in FEV(1) (PC(20)) (r(s) = -0.52, p < 0.001). Recent use of short-acting beta(2)-agonist increased the risk for excessive bronchoconstriction 10.2-fold (CI: 1.2 to 109.8). In conclusion, sputum induction can be safely and successfully performed in patients with severe, difficult-to-control asthma if a standardized protocol is used. However, severe bronchoconstriction may occur despite regular use of long-acting beta(2)-agonist and pretreatment with salbutamol 400 microg. In particular, patients who have used additional short-acting beta(2)-agonists as rescue medication during the days preceding the induction, are at high risk.

The juxtamembrane lysine and arginine residues of surfactant protein C precursor influence palmitoylation via effects on trafficking

Surfactant protein (SP)-C propeptide (proSP-C) becomes palmitoylated on cysteines 5 and 6 before mature SP-C is formed by several proteolytic steps. To study the structural requirements for the palmitoylation of proSP-C, his-tagged human proSP-C (his-proSP-C) and his-proSP-C mutants were expressed in Chinese hamster ovary cells and analyzed by metabolic labeling with [(3)H]palmitate and immunocytochemistry. Substitution of cysteines 5 and 6 by serines showed that these were the only two cysteine residues palmitoylated in his-proSP-C. Substitution of the juxtamembrane basic residues lysine and arginine by uncharged glutamines led to a large decrease in palmitoylation level of proSP-C. The addition of brefeldin A nearly abolished this decrease for the lysine and double mutant; the palmitoylation of the arginine mutant increased also, but not to wild-type (WT) levels. Fluorescence immunocytochemistry showed that WT proSP-C was localized in punctate vesicles throughout the cell, whereas the mutant lacking the juxtamembrane positive charges was found more perinuclear, probably in the endoplasmic reticulum (ER). This indicates that the two basic juxtamembrane residues influence palmitoylation of proSP-C by preventing the transport of proSP-C out of the ER, implying that proSP-C becomes palmitoylated normally in a compartment distal to the ER.

Psychopathology in patients with severe asthma is associated with increased health care utilization

Severe asthma accounts for the majority of health costs for this disease, which is mainly related to the treatment of failed control. Several psychosocial factors have been associated with poor asthma control, but the question remains whether psychiatric disorder in patients with severe asthma predisposes for increased health care utilization. In the present study we compared outpatients with severe asthma with and without psychological dysfunctioning with respect to health care utilization. All patients used high dose inhaled corticosteroids and long-acting bronchodilators for more than 1 yr, and had difficult-to-control asthma, requiring one or more courses of corticosteroids during the past year or maintenance therapy with prednisone. Medical history was taken and health care utilization questionnaires were completed. The General Health Questionnaire (GHQ) was used to identify psychiatric cases (GHQ-12 score of > or = 6). There were no differences between the psychiatric cases (n = 21) and the noncases (n = 77) with respect to demographic and objective disease characteristics. However, the psychiatric cases had increased odds ratios (OR) for frequent visits to GP (OR = 5.9), frequent emergency visits (OR = 5.3), frequent exacerbations (OR = 12.4), and frequent hospitalizations (OR = 4.8) as compared with the nonpsychiatric patients. The present findings suggest that the morbidity and costs of asthma might be related to the level of psychological dysfunctioning in patients with severe asthma rather than to asthma severity per se, thereby identifying an area of potential intervention.

Persistent airflow limitation in adult-onset nonatopic asthma is associated with serologic evidence of Chlamydia pneumoniae infection

BACKGROUND

Persistent airflow limitation may develop in patients with asthma, particularly in adults with nonatopic (intrinsic) disease. Although the underlying mechanisms are still unknown, respiratory infections might be involved.

OBJECTIVE

We investigated the annual loss of lung function in relation to seropositivity to Chlamydia pneumoniae in different subgroups of patients with severe asthma according to age at onset of asthma and atopic status.

METHODS

One hundred one nonsmoking outpatients with a pulmonologist's diagnosis of severe asthma (32 men and 69 women; mean age, 46.0 years; range, 18-75 years) were included in a cross-sectional study. C pneumoniae-specific serum IgG and IgA were measured by means of ELISA. The estimated decline in lung function was calculated from the relationship between postbronchodilator FEV(1)/vital capacity (percent predicted) and the duration of asthma and expressed as the slope of the regression line.

RESULTS

Patients with adult-onset nonatopic asthma and positive IgG antibodies to C pneumoniae had a significantly steeper slope of the regression line compared with the other subgroups of asthmatic patients (P =.001), being indicative of a 4-fold greater estimated decline in postbronchodilator FEV(1)/vital capacity (2.3% vs 0.5% predicted per year of asthma duration).

CONCLUSION

These results suggest that C pneumoniae infection might promote the development of persistent airflow limitation in patients with nonatopic adult-onset asthma. It remains to be established whether viable pathogens that are accessible for therapeutic intervention are still present in the lower airways.

Similar psychological characteristics in mild and severe asthma

OBJECTIVE

Psychological factors have been implicated as potentially contributing to asthma severity. In the present study, we investigated whether patients with mild and severe asthma differ with regard to several psychological characteristics.

METHODS

Ninety outpatients with severe asthma (74% female, mean [S.D.] age: 46.5 [13.7] years) and 37 outpatients with mild asthma (73% female, age: 39.4 [13.9] years) were compared with respect to general psychological health, anxiety sensitivity, hyperventilation symptoms, personality, and locus-of-control orientation, all measured by well-validated self-report questionnaires. Analysis of (co)variance (ANCOVA) was used to assess between-groups differences.

RESULTS

No significant differences in psychological characteristics were found between patients with mild and severe asthma. Only on the subscale for external locus-of-control orientation, severe asthmatic patients differed from those with mild disease (P=.005) in showing less trust in physicians and medication with regard to influencing their asthma.

CONCLUSION

The results suggest that mild and severe asthmatic patients cannot be differentiated on the basis of psychopathology or personality. Whether or not the observed lack of confidence in the influence of physicians or medication on asthma course is cause or consequence of disease severity, remains to be established.

Effects of an interleukin-5 blocking monoclonal antibody on eosinophils, airway hyper-responsiveness, and the late asthmatic response

BACKGROUND

Interleukin-5 (IL-5) is essential for the formation of eosinophils, which are thought to have a major role in the pathogenesis of asthma and other allergic diseases. We aimed to assess the effects of monoclonal antibody to IL-5 on blood and sputum eosinophils, airway hyper-responsiveness, and the late asthmatic reaction to inhaled allergen in patients with mild asthma.

METHODS

We did a double-blind randomised placebo-controlled trial, in which a single intravenous infusion of humanised (IgG-K) monoclonal antibody to IL-5 (SB-240563) was given at doses of 2.5 mg/kg (n=8) or 10.0 mg/kg (n=8). The effects of treatment on responses to inhaled allergen challenge, sputum eosinophils, and airway hyper-responsiveness to histamine were measured at weeks 1 and 4 with monitoring of blood eosinophil counts for up to 16 weeks.

FINDINGS

Monoclonal antibody against IL-5 lowered the mean blood eosinophil count at day 29 from 0.25x10(9)/L (95% CI 0.16-0.34) in the placebo group to 0.04x10(9)/L (0.00-0.07) in the 10 mg/kg group (p<0.0001), and prevented the blood eosinophilia that follows allergen challenge. After inhaled allergen challenge, 9 days after treatment, the percentage sputum eosinophils were 12.2% in the placebo group and lowered to 0.9% (-1.2 to 3.0; p=0.0076) in the 10 mg/kg group, and this effect persisted at day 30 after the dose. There was no significant effect of monoclonal antibody to IL-5 on the late asthmatic response or on airway hyper-responsiveness to histamine.

INTERPRETATION

A single dose of monoclonal antibody to IL-5 decreased blood eosinophils for up to 16 weeks and sputum eosinophils at 4 weeks, which has considerable therapeutic potential for asthma and allergy. However, our findings question the role of eosinophils in mediating the late asthmatic response and causing airway hyper-responsiveness.

Is leg length discrepancy associated with the side of radiating pain in patients with a lumbar herniated disc?

STUDY DESIGN

The association between leg length discrepancy and the side of the radiating pain in lumbar disc herniation was investigated in a case series.

OBJECTIVES

To investigate whether pain tends to radiate into the longer or shorter leg in patients with a lumbar herniated disc.

SUMMARY OF BACKGROUND DATA

No previous studies have investigated the association between leg length discrepancy and side of radiating pain in patients with a herniated disc. Results of studies of low back pain with radiation and leg length discrepancy are inconsistent concerning this association.

METHODS

Of 132 consecutive patients admitted to a district hospital for surgical management of a lumbar herniated disc, leg length discrepancy was assessed using the indirect method as described by Calliet.

RESULTS

Seventy-three patients (55%) were men, and 59 (45%) were women. The mean age was 40 years, and 99% of all herniated discs appeared at L4-L5 (n = 60) or L5-S1 (n = 71). In 64 (62%) of the 104 patients with a leg length discrepancy of 1 mm or more, the pain radiated in the shorter leg (P = 0.02). In subgroups of patients with larger leg length discrepancies, similar results were found but because of smaller sample sizes, these findings did not each statistical significance. In 32 of the 57 men (56.1%), the pain radiated to the shorter leg (P = 0.43); this was observed in 33 of the 47 women (70.2%; P = 0.01).

CONCLUSION

The results of this study showed a statistically significant association between leg length discrepancy and the side of radiating pain in a case series of patients with lumbar herniated discs. The relation was more pronounced and statistically significant in women only.