Adrenergic responsiveness: FEV1 and symptom differences in Whites and African Americans with mild asthma

Immunogenetics and pharmacogenetics of allergic asthma in Africa

Asthma is a common chronic condition in children and in an African setting is often highly prevalent in urban areas as compared to rural areas. Asthma is a heritable disease and the genetic risk is often exacerbated by unique localised environmental factors. The Global Initiative for Asthma (GINA) recommendation for the control of asthma includes inhaled corticosteroids (ICS) alone or together with short-acting β₂-agonists (SABA) or long-acting β₂-agonists (LABA). While these drugs can relieve asthma symptoms, there is evidence of reduced efficacy in people of African ancestry. Whether this is due to immunogenetics, genomic variability in drug metabolising genes (pharmacogenetics) or genetics of asthma-related traits is not well defined. Pharmacogenetic evidence of first-line asthma drugs in people of African ancestry is lacking and is further compounded by the lack of representative genetic association studies in the continent. In this review, we will discuss the paucity of data related to the pharmacogenetics of asthma drugs in people of African ancestry, mainly drawing from African American data. We will further discuss how this gap can be bridged to improve asthma health outcomes in Africa.

Uncovering Outcome Disparities of β2 Adrenergic Agonists in Blacks: A Systematic Review

PURPOSE

Outcome differences driven by variation in Blacks' biologic response to treatment may contribute to persistent racial disparities in asthma morbidity and mortality. This review assessed systematic variation in β₂ agonist treatment outcomes among Blacks compared to other groups.

METHODS

We conducted a systematic review of studies reporting differential response to β₂ agonists among Blacks, including studies identifying pharmacogenetic variants.

RESULTS

Of 3158 papers, 20 compared safety or efficacy of β₂ agonists among Blacks as compared with other subgroups. Six papers evaluating efficacy of short-acting β₂ agonists (SABA) found similar or improved results among Blacks compared with other groups, while one small study found reduced response to SABA therapy among Blacks. Reports of safety and efficacy of long-acting β₂ agonists (LABA) indicated similar results among Blacks in four papers, while four reports found reduced safety among Blacks, as compared with other groups. Four papers assessed genomic variation and relative treatment response in Blacks, with two finding significant effects of the p.Arg16Gly variant in ADRB2 on β₂ agonist response and one finding significant gene-gene IL6/IL6R interaction effects on albuterol response.

CONCLUSIONS

Evidence suggests the potential for differences in β₂ agonist outcomes among Blacks compared with other groups. This literature, however, remains small and significantly underpowered for substantive conclusions. There are notable opportunities for adequately-powered investigations exploring safety and efficacy of β₂ agonists among Blacks, including pharmacogenomic modifiers of response.

Considerations for Care: Management of Asthma in the Child with Sickle Cell Disease

Asthma is difficult to diagnose in the child with sickle cell disease because symptoms and pulmonary function abnormalities are similar to the spectrum of pulmonary manifestations in sickle cell disease. There are no published reports of controlled trials of asthma medications in children with sickle cell disease. Thus, treatment decisions should be guided by the Expert Panel Report 3: Guidelines for the Diagnosis and Management of Asthma (www.nhlbi.nih.gov/guidelines/asthma/asthgdln.pdf). However, issues specific to children with sickle cell disease should be considered. Initial strategies should focus on control of environmental triggers, as effectiveness on asthma outcomes is proven and the cost for implementation can be low. Use of short- and long-acting β₂-agonists may prolong QTc, particularly in this population of children who already have a higher prevalence of prolonged QTc than the general population. Long-acting β₂-agonist use has been associated with life-threatening asthma exacerbations with potentially higher risks in African Americans. Montelukast has been reported to increase suicidal thinking and behavior, and persons with asthma and sickle cell disease are already at risk for these events. Oral corticosteroids in the treatment of acute chest syndrome may increase risk of readmission even in children with asthma. The lack of prospective controlled trials of asthma drug treatment in children with asthma and sickle cell disease compels us to move this issue forward.

Bronchial hyperresponsiveness, word descriptors, and ethnicity: women with mild asthma

BACKGROUND

Few studies have examined the ethnic differences in symptom reporting and airway hyperresponsiveness (AHR) for women with mild asthma during a methacholine (McH) challenge.

OBJECTIVE

The purpose of this sub-analysis was to determine: (1) whether AHR to McH varied by the ethnicity of women with mild asthma and (2) whether ethnic word descriptors (EWDs) varied by the ethnicity during induced bronchoconstriction.

METHODS

Specific inclusion criteria included the following: FEV(1) (forced expiratory volume in 1 second) ≥ 70% predicted normal, PC(30) ≤ 8 mg/McH, β(2) inhaler only, and self-reported ethnicity of African American (AFAM), Mexican American-Hispanic-Latino (MexAMLat), Asian-Pacific Islander (Asian PI), or white. Serial pulmonary function testing (PFT) and Borg, visual analogue scale (VAS), and EWDs were collected.

RESULTS

A total of 44 women, mean age of 31.3 years old, with a mean baseline FEV(1) of 2.85 L comprised this sub-analysis. Ethnic-racial diversity included: 12 AFAMs, 5 MexAMLat, 13 Asian-PIs, and 14 whites. All had atopy ≥ 2 pinprick responses of 3 mm. At PC(30), Asian-PI women required a significantly (p < .05) smaller mean dose of McH 1.9 mg/mL. MexAMLat women required an McH dose of 1.6 mg/mL. At PC(30), McH dose was 2.9 mg/mL for AFAMs and 3.0 mg/mL for whites, respectively. Asian-PIs who used only upper airway EWDs at PC(30) vere itchy throat, itchy chin, and constricted throat (p < .001). AFAMs significant EWDs were itchy throat, itchy chin/face, and tight throat (p < .01). Lower airway EWD was used by both MexAMLat and whites. Significant EWD for Whites were tight chest (p < .01) and hard to inhale/lungs tight (p < .001).

CONCLUSION

Asian-PI women required a significantly smaller dose (p < .05) of McH to induce a PC(30). AFAM and whites required a comparable dose of Mch at PC(30). Asian-PI and AFAM women used only upper airway EWD. Asian-PI women may be at a greater risk for acute asthma episodes that are not recognized or treated due to their upper airway symptom reporting.

Asthma in sickle cell disease: implications for treatment

Objective. To review issues related to asthma in sickle cell disease and management strategies. Data Source. A systematic review of pertinent original research publications, reviews, and editorials was undertaken using MEDLlNE, the Cochrane Library databases, and CINAHL from 1947 to November 2010. Search terms were [asthma] and [sickle cell disease]. Additional publications considered relevant to the sickle cell disease population of patients were identified; search terms included [sickle cell disease] combined with [acetaminophen], [pain medications], [vitamin D], [beta agonists], [exhaled nitric oxide], and [corticosteroids]. Results. The reported prevalence of asthma in children with sickle cell disease varies from 2% to approximately 50%. Having asthma increases the risk for developing acute chest syndrome , death, or painful episodes compared to having sickle cell disease without asthma. Asthma and sickle cell may be linked by impaired nitric oxide regulation, excessive production of leukotrienes, insufficient levels of Vitamin D, and exposure to acetaminophen in early life. Treatment of sickle cell patients includes using commonly prescribed asthma medications; specific considerations are suggested to ensure safety in the sickle cell population. Conclusion. Prospective controlled trials of drug treatment for asthma in patients who have both sickle cell disease and asthma are urgently needed.

Descriptors of breathlessness in children with persistent asthma

BACKGROUND

In adult patients, the consistent use of language to describe dyspnea enhances patient-provider communication and contributes to diagnostic and therapeutic decisions. The objective of this research was to determine whether pediatric patients similarly display consistency in the language used to describe "uncomfortable awareness of breathing."

METHODS

One hundred children between the ages of 8 and 15 years with moderate to severe persistent asthma enrolled in an asthma education research program completed questionnaires regarding descriptors of asthma on each of two occasions. In addition to the breathlessness questionnaires, demographic information, self-reported asthma severity, ED visits, missed school days, anthropometrics, and spirometry were obtained for each participant.

RESULTS

Children were reliable in their choice of the descriptors that they applied to their breathing discomfort across two occasions, and they selected the same descriptors that were used by adults with asthma in previous studies. Children with greater self-reported asthma severity endorsed more descriptors to characterize breathing discomfort than did children with less severe asthma, but no differences were found among children based on demographic or anthropometric variables.

CONCLUSIONS

Children with moderate to severe persistent asthma are reliable in their choice of descriptors of breathlessness. Knowledge of their experience of symptoms may be helpful clinically in the assessment and management of asthma.

Ethnic differences in methacholine responsiveness and word descriptors in African Americans, Hispanic-Mexican Americans, Asian-Pacific Islanders, and Whites with mild asthma

OBJECTIVE

There is little asthma research that compares ethnic differences in airway responsiveness and word descriptors among African Americans, Hispanic-Mexican Americans, Asian-Pacific Islanders, and Whites. Thus, identifying ethnic differences in symptom descriptors and airway responsiveness may improve health outcomes by educating health professionals about treatment decisions that are culturally and ethnically sensitive.

METHODS

Specific Inclusion criteria-forced expiratory volume in one second (FEV(1)) >or= 70% predicted normal; provocative concentration causing a 30% fall in FEV(1) (PC(30)) <or= 8 mg/ml for methacholine (MCh), using only a beta(2)- inhaler, and self-reported ethnicity of African American, Hispanic-Mexican American, Asian-Pacific Islander, or White. Serial pulmonary function test (PFT) and Borg, Visual Analogue Scale (VAS), and Ethnic Word Descriptors (EWDs) were collected.

RESULTS

One hundred eighteen consented, 106 completed procedures, and 90 had a positive PC(30) and were enrolled. Asian-Pacific Islanders had significantly greater airway responsiveness (p <.02). Baseline FEV(1), MCh dose, and PC(30) correlated with race (p <.001); baseline FEV(1) and ethnicity predicted airway responsiveness (p <.001). EWDs differed significantly by ethnicity. Upper airway EWDs for Asian-Pacific Islanders: itchy throat (p < .04), itchy (p <.02), itchy back throat (p <.04), voice tight, tight throat (p <.001), and cough (p <.04). Upper airway EWDs for African Americans: add itchy throat (p <.002), itchy neck (p <.001), tight throat (p <.003), voice tight (p <.02), and cough (p <.04). Hispanic-Mexican Americans used both upper and lower airway EWDs; Whites used only lower airway EWDs.

CONCLUSION

This study provides new insights about ethnic differences in airway responsiveness and EWDs. Asian-Pacific Islanders required a significantly smaller dose of MCh to achieve a PC(30) compared to the other three ethnic groups. The upper airway EWDs used by African Americans, Asian-Pacific Islanders, and Hispanic-Mexican Americans indicate a shared language of symptoms. A new language of breathlessness that incorporates both cultural and ethnic differences is needed to address the present disparity in the management of asthma symptoms.

Population pharmacodynamic model of bronchodilator response to inhaled albuterol in children and adults with asthma

BACKGROUND

Because interpatient variability in bronchodilation from inhaled albuterol is large and clinically important, we characterized the albuterol dose/response relationship by pharmacodynamic modeling and quantified variability.

METHODS

Eighty-one patients with asthma (24% African American [AA]; 8 to 65 years old; baseline FEV1, 40 to 80% of predicted) received 180 microg of albuterol from a metered-dose inhaler (MDI), and then 90 microg every 15 min until maximum improvement or 540 microg was administered; all then received 2.5 mg of nebulized albuterol. FEV1 was measured 15 min after each dose. The population cumulative dose/response data were fitted with a sigmoid maximum effect of albuterol (Emax) [maximum percentage of predicted FEV1 effect] model by nonlinear mixed-effects modeling. The influence of covariates on maximum percentage of predicted FEV1 reached after albuterol administration (Rmax) and cumulative dose of albuterol required to bring about 50% of maximum effect of albuterol (ED50) and differences between AA and white patients were explored.

RESULTS

ED50 was 141 microg, and Emax was 24.0%. Coefficients of variation for ED50 and Emax were 40% and 56%, respectively. Ethnicity was a statistically significant covariate (p < 0.05). AA and white patients reached 82.4% and 91.9% of predicted FEV1, respectively (p = 0.0004); and absolute improvement in percentage of predicted FEV1 was 16.6% in AA patients vs 26.7% in white patients (p < 0.0003). There were no baseline characteristic differences between AA and white patients. Nebulized albuterol increased FEV1 > or = 200 mL in 21% of participants. Heart rate and BP were unchanged from baseline after maximal albuterol doses.

CONCLUSIONS

Our model predicts that 180 microg of albuterol by MDI produces a 14.4% increase in percentage of predicted FEV1 over baseline (11.7% in AA patients, and 17.5% in white patients). Emax varies widely between asthmatic patients. AA patients are less responsive to maximal doses of inhaled albuterol than white patients.