Integrated genome-wide association, coexpression network, and expression single nucleotide polymorphism analysis identifies novel pathway in allergic rhinitis

BACKGROUND

Allergic rhinitis is a common disease whose genetic basis is incompletely explained. We report an integrated genomic analysis of allergic rhinitis.

METHODS

We performed genome wide association studies (GWAS) of allergic rhinitis in 5633 ethnically diverse North American subjects. Next, we profiled gene expression in disease-relevant tissue (peripheral blood CD4+ lymphocytes) collected from subjects who had been genotyped. We then integrated the GWAS and gene expression data using expression single nucleotide (eSNP), coexpression network, and pathway approaches to identify the biologic relevance of our GWAS.

RESULTS

GWAS revealed ethnicity-specific findings, with 4 genome-wide significant loci among Latinos and 1 genome-wide significant locus in the GWAS meta-analysis across ethnic groups. To identify biologic context for these results, we constructed a coexpression network to define modules of genes with similar patterns of CD4+ gene expression (coexpression modules) that could serve as constructs of broader gene expression. 6 of the 22 GWAS loci with P-value ≤ 1x10-6 tagged one particular coexpression module (4.0-fold enrichment, P-value 0.0029), and this module also had the greatest enrichment (3.4-fold enrichment, P-value 2.6 × 10-24) for allergic rhinitis-associated eSNPs (genetic variants associated with both gene expression and allergic rhinitis). The integrated GWAS, coexpression network, and eSNP results therefore supported this coexpression module as an allergic rhinitis module. Pathway analysis revealed that the module was enriched for mitochondrial pathways (8.6-fold enrichment, P-value 4.5 × 10-72).

CONCLUSIONS

Our results highlight mitochondrial pathways as a target for further investigation of allergic rhinitis mechanism and treatment. Our integrated approach can be applied to provide biologic context for GWAS of other diseases.

Genome-wide association study and admixture mapping identify different asthma-associated loci in Latinos: the Genes-environments & Admixture in Latino Americans study

BACKGROUND

Asthma is a complex disease with both genetic and environmental causes. Genome-wide association studies of asthma have mostly involved European populations, and replication of positive associations has been inconsistent.

OBJECTIVE

We sought to identify asthma-associated genes in a large Latino population with genome-wide association analysis and admixture mapping.

METHODS

Latino children with asthma (n = 1893) and healthy control subjects (n = 1881) were recruited from 5 sites in the United States: Puerto Rico, New York, Chicago, Houston, and the San Francisco Bay Area. Subjects were genotyped on an Affymetrix World Array IV chip. We performed genome-wide association and admixture mapping to identify asthma-associated loci.

RESULTS

We identified a significant association between ancestry and asthma at 6p21 (lowest P value: rs2523924, P < 5 × 10(-6)). This association replicates in a meta-analysis of the EVE Asthma Consortium (P = .01). Fine mapping of the region in this study and the EVE Asthma Consortium suggests an association between PSORS1C1 and asthma. We confirmed the strong allelic association between SNPs in the 17q21 region and asthma in Latinos (IKZF3, lowest P value: rs90792, odds ratio, 0.67; 95% CI, 0.61-0.75; P = 6 × 10(-13)) and replicated associations in several genes that had previously been associated with asthma in genome-wide association studies.

CONCLUSIONS

Admixture mapping and genome-wide association are complementary techniques that provide evidence for multiple asthma-associated loci in Latinos. Admixture mapping identifies a novel locus on 6p21 that replicates in a meta-analysis of several Latino populations, whereas genome-wide association confirms the previously identified locus on 17q21.

Race and association of angiotensin converting enzyme/angiotensin receptor blocker exposure with outcome in heart failure

PURPOSE

Angiotensin converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) have been established as a mainstay of heart failure treatment. Current data are limited and conflicting regarding the consistency of ACE/ARB benefit across race groups in heart failure. This study aims to clarify this point.

METHODS

This was a retrospective study of insured patients with a documented ejection fraction of less than 50%, hospitalized for heart failure between January 2000 and June 2008. Pharmacy claims data were used to estimate ACE/ARB exposure over 6-month rolling windows. The association between ACE/ARB exposure and all-cause hospitalization or death was assessed by proportional hazards regression, with adjustment for baseline covariates and β-blocker exposure. Further analyses were stratified by race, and included an ACE/ARB × Race interaction term.

RESULTS

A total of 1095 patients met inclusion criteria (619 African-American individuals). Median follow-up was 2.1 years. In adjusted models, ACE/ARB exposure was associated with lower risk of death or hospitalization in both groups (African-Americans hazard ratio 0.47, P < 0.001; whites hazard ratio 0.55, P < 0.001). A formal test for interaction was consistent with similar effects in each group (P = 0.861, β = 0.04).

CONCLUSION

ACE/ARB exposure was equally associated with a protective effect in preventing death or rehospitalization among heart failure patients with systolic dysfunction in both African-American patients and whites.

Policies and events affecting prescription opioid use for non-cancer pain among an insured patient population

BACKGROUND

Rising prescription opioid use and abuse have prompted widespread concern. However, to date there have been few rigorous investigations into the policies and events which may have contributed to these trends.

OBJECTIVE

This study investigates trends in opioid use and related adverse events among individuals with non-cancer pain before and after implementation of major national policies.

STUDY DESIGN

The study used a longitudinal prospective study design. The analysis was limited to adults (age = 18 years) without a recorded cancer diagnosis. Pharmacy claims were used to assess rates of prescription opioid use, the strength of opioids dispensed, the proportion using opioids chronically, and related adverse events. Time trend analysis was used to identify changes in these rates over time. The study was Institutional Review Board approved.

SETTING

Study patients were members of a large, health maintenance organization in southeast Michigan, with longitudinal records of prescription opioid use.

RESULTS

The analysis comprised 523,623 individuals and 1,066,700 opioid pharmacy fills from January 1, 1997, to December 31, 2011. Contemporaneous with the implementation of health organization accreditation criteria requiring assessment and treatment of pain in all patients beginning January 2001, we observed a consistent and unabated increase in the rate of opioid fills and the proportion of chronic use. A parallel increase in the annual rate of adverse events was also observed. Similarly, we observed a continuous rise in the average strength of opioid fills following January 2001 with the exception of a single drop in December 2010, which was attributable to the withdrawal of propoxyphene from the U.S. market.

LIMITATIONS

This was an observational study and not a trial. Other long-term opioid-related benefits or harms, including functional status, quality of life, and substance use disorder, were not assessed.

CONCLUSIONS

This study provides temporal evidence for a rise in prescription opioid use after implementation of health organization accreditation criteria requiring standardized management of all individuals with pain.

Campylobacter infection has different outcomes in fast- and slow-growing broiler chickens

Campylobacter spp. are frequently carried by poultry, but they are not believed to cause significant disease in these animals. Modern poultry breeds have been selected to grow rapidly under intensive conditions, but recently, consumers have moved toward purchasing birds produced in higher welfare, free-range or organic systems. Birds reared in these systems tend to be a slower growing breed and are fed a different diet. Birds reared in such systems are stocked at a lower density compared with the standard conventional broilers, and they have access to environmental enrichment, such as perches. In previous research, these slower growing birds have been shown to have different levels of Campylobacter carriage in commercial rearing conditions, but the reasons for, and effect of, these different levels are unknown; is it the bird breed, diet, or environmental conditions? In this study, experimental flocks of fast- and slow-growing breeds of broiler chickens were reared to a standard commercial slaughter weight, with their weight gain being measured during the growing period. At 21 days, birds were either infected with Campylobacter jejuni or given a placebo as control. Cohorts of birds were euthanatized at various intervals, and samples were taken for examination for Campylobacter. The fast-growing birds gained weight more rapidly than the slow-growing birds. By 2 days postinfection (dpi), C. jejuni was detected in the caeca and by enrichment from the liver and spleen samples from both breeds of birds. Low-level colonization persisted in the spleen and liver samples but was undetectable by 28 dpi. Fast- and slow-growing birds did not show detectably different levels of Campylobacter carriage. Infection with C. jejuni affected the incidence of hock marks and pododermatitis in both breeds of birds, but the differences were greater with the fast-growing breed compared with the uninfected control birds. In addition, the incidence of pododermatitis was significantly higher in Campylobacter-positive fast-growing birds than in their slower-growing counterparts. The results show that infection with Campylobacter can have an indirect welfare effect on birds via increased incidence of hock marks and pododermatitis.

Gene-based association identifies SPATA13-AS1 as a pharmacogenomic predictor of inhaled short-acting beta-agonist response in multiple population groups

Inhaled short-acting beta-agonist (SABA) medication is commonly used in asthma patients to rapidly reverse airway obstruction and improve acute symptoms. We performed a genome wide association study of SABA medication response using gene-based association tests. A linear mixed model approach was first used for SNP associations, and results were later combined using GATES to generate gene-based associations. Our results identified SPATA13-AS1 as being significantly associated with SABA bronchodilator response in 328 healthy African Americans. In replication, this gene was associated with SABA response among 2 separate groups of African Americans with asthma (n=1,073, p=0.011 and n=1,968, p=0.014), 149 healthy African Americans (p=0.003), and 556 European Americans with asthma (p=0.041). SPATA13-AS1 was also associated with longitudinal SABA medication usage in 2 separate groups of African Americans with asthma (n=658, p=0.047 and n=1,968, p=0.025). Future studies are needed to delineate the precise mechanism by which SPATA13-AS1 may influence SABA response.

Socioeconomic status and childhood asthma in urban minority youths. The GALA II and SAGE II studies

RATIONALE

The burden of asthma is highest among socioeconomically disadvantaged populations; however, its impact is differentially distributed among racial and ethnic groups.

OBJECTIVES

To assess the collective effect of maternal educational attainment, annual household income, and insurance type on childhood asthma among minority, urban youth.

METHODS

We included Mexican American (n = 485), other Latino (n = 217), and African American (n = 1,141) children (aged 8-21 yr) with and without asthma from the San Francisco Bay Area. An index was derived from maternal educational attainment, annual household income, and insurance type to assess the collective effect of socioeconomic status on predicting asthma. Logistic regression stratified by racial and ethnic group was used to estimate adjusted odds ratios (aOR) and their 95% confidence intervals (CI). We further examined whether acculturation explained the socioeconomic-asthma association in our Latino population.

MEASUREMENTS AND MAIN RESULTS

In the adjusted analyses, African American children had 23% greater odds of asthma with each decrease in the socioeconomic index (aOR, 1.23; 95% CI, 1.09-1.38). Conversely, Mexican American children have 17% reduced odds of asthma with each decrease in the socioeconomic index (aOR, 0.83; 95% CI, 0.72-0.96) and this relationship was not fully explained by acculturation. This association was not observed in the other Latino group.

CONCLUSIONS

Socioeconomic status plays an important role in predicting asthma, but has different effects depending on race and ethnicity. Further steps are necessary to better understand the risk factors through which socioeconomic status could operate in these populations to prevent asthma.

Comparison of β-blocker effectiveness in heart failure patients with preserved ejection fraction versus those with reduced ejection fraction

BACKGROUND

The aim of this study was to compare the benefit of beta-blockers (BB) in heart failure (HF) with preserved versus reduced ejection fraction (EF).

METHODS AND RESULTS

This was a retrospective study of insured patients who were hospitalized for HF from January 2000 to June 2008. Pharmacy claims were used to estimate BB exposure over 6-month rolling windows. The association between BB exposure and all-cause hospitalization or death was tested with the use of time-updated proportional hazards regression, with adjustment for baseline covariates and other HF medication exposure. The groups were compared by stratification (EF <50% vs ≥50%) and with the use of an EF-group × BB exposure interaction term. A total of 1,835 patients met the inclusion criteria, 741 (40%) with a preserved EF. Median follow-up was 2.1 years. In a fully adjusted multivariable model, BB exposure was associated with a decreased risk of death or hospitalization in both groups (EF <50%: hazard ratio [HR] 0.53 [P < .0001]; EF ≥50%: HR 0.68 [P = .009]). There was no significant difference in this protective association between groups (interaction: P = .32).

CONCLUSIONS

BB exposure was associated with a similar protective effect regarding time to death or hospitalization in HF patients regardless of whether EF was preserved or reduced. An adequately powered randomized trial of BB in HF with preserved EF is warranted.

Factors associated with degree of atopy in Latino children in a nationwide pediatric sample: the Genes-environments and Admixture in Latino Asthmatics (GALA II) study

BACKGROUND

Atopy varies by ethnicity, even within Latino groups. This variation might be due to environmental, sociocultural, or genetic factors.

OBJECTIVE

We sought to examine risk factors for atopy within a nationwide study of US Latino children with and without asthma.

METHODS

Aeroallergen skin test responses were analyzed in 1830 US Latino subjects. Key determinants of atopy included country/region of origin, generation in the United States, acculturation, genetic ancestry, and site to which subjects migrated. Serial multivariate zero-inflated negative binomial regressions stratified by asthma status examined the association of each key determinant variable with the number of positive skin test responses. In addition, the independent effect of each key variable was determined by including all key variables in the final models.

RESULTS

In baseline analyses African ancestry was associated with 3 times (95% CI, 1.62-5.57) as many positive skin test responses in asthmatic participants and 3.26 times (95% CI, 1.02-10.39) as many positive skin test responses in control participants. Generation and recruitment site were also associated with atopy in crude models. In final models adjusted for key variables, asthmatic patients of Puerto Rican (exp[β] [95% CI], 1.31 [1.02-1.69]) and mixed (exp[β] [95% CI], 1.27 [1.03-1.56]) ethnicity had a greater probability of positive skin test responses compared with Mexican asthmatic patients. Ancestry associations were abrogated by recruitment site but not region of origin.

CONCLUSIONS

Puerto Rican ethnicity and mixed origin were associated with degree of atopy within US Latino children with asthma. African ancestry was not associated with degree of atopy after adjusting for recruitment site. Local environment variation, represented by site, was associated with degree of sensitization.

Efficient inference of local ancestry

MOTIVATION

The inference of local ancestry of admixed individuals at every locus provides the basis for admixture mapping. Local ancestry information has been used to identify genetic susceptibility loci.

RESULTS

In this study, we developed a statistical method, efficient inference of local ancestry (EILA), which uses fused quantile regression and k-means classifier to infer the local ancestry for admixed individuals. We also conducted a simulation study using HapMap data to evaluate the performance of EILA in comparison with two competing methods, HAPMIX and LAMP. In general, the performance declined as the ancestral distance decreased and the time since admixture increased. EILA performed as well as the other two methods in terms of computational efficiency. In the case of closely related ancestral populations, all the three methods performed poorly. Most importantly, when the ancestral distance was large or moderate, EILA had higher accuracy and lower variation in comparison with the other two methods.

AVAILABILITY AND IMPLEMENTATION

EILA is implemented as an R package, which is freely available from the Comprehensive R Archive Network (http://cran.r-project.org/).

CONTACT

jyangstat@gmail.com.

Genome-wide association study of lung function phenotypes in a founder population

BACKGROUND

Lung function is a long-term predictor of mortality and morbidity.

OBJECTIVE

We sought to identify single nucleotide polymorphisms (SNPs) associated with lung function.

METHODS

We performed a genome-wide association study (GWAS) of FEV1, forced vital capacity (FVC), and FEV1/FVC in 1144 Hutterites aged 6 to 89 years, who are members of a founder population of European descent. We performed least absolute shrinkage and selection operation regression to select the minimum set of SNPs that best predict FEV1/FVC in the Hutterites and used the GRAIL algorithm to mine the Gene Ontology database for evidence of functional connections between genes near the predictive SNPs.

RESULTS

Our GWAS identified significant associations between FEV1/FVC and SNPs at the THSD4-UACA-TLE3 locus on chromosome 15q23 (P = 5.7 × 10(-8) to 3.4 × 10(-9)). Nine SNPs at or near 4 additional loci had P < 10(-5) with FEV1/FVC. Only 2 SNPs were found with P < 10(-5) for FEV1 or FVC. We found nominal levels of significance with SNPs at 9 of the 27 previously reported loci associated with lung function measures. Among a predictive set of 80 SNPs, 6 loci were identified that had a significant degree of functional connectivity (GRAIL P < .05), including 3 clusters of β-defensin genes, 2 chemokine genes (CCL18 and CXCL12), and TNFRSF13B.

CONCLUSION

This study identifies genome-wide significant associations and replicates results of previous GWASs. Multimarker modeling implicated for the first time common variation in genes involved in antimicrobial immunity in airway mucosa that influences lung function.

Real-world effects of once vs greater daily inhaled corticosteroid dosing on medication adherence

BACKGROUND

Nonadherence to inhaled corticosteroids (ICSs) for asthma maintenance therapy is common and is associated with poor asthma outcomes. Simplifying dosing regimens for some chronic disease conditions has resulted in better adherence; however, little is known regarding the effect of ICS dosing on adherence for the treatment of asthma.

OBJECTIVE

To determine whether once daily dosing is associated with higher adherence to ICS therapy when compared with 2 or more times daily dosing among patients with asthma.

METHODS

Six years of pharmacy claims data were linked with prescription information to estimate ICS therapy adherence for patients with asthma 12 to 56 years of age who were members of a large health maintenance organization. Patient follow-up continued from the initial ICS fill until one of the following: the last ICS fill in the observation period, a switch of ICS dosing regimen, or the initiation of ICS and long-acting β-agonist combination therapy. Adherence was estimated by calculating a continuous multiple-interval measure of medication availability. Regression models were used to assess the relationship between adherence in patients treated with once daily vs 2 or more times daily ICS therapy.

RESULTS

Among the 1,302 patients who met the inclusion criteria, 17% were prescribed once daily therapy, and 83% were prescribed 2 or more times daily therapy. Models comparing ICS adherence among individuals following once daily and 2 or more times daily ICS regimens suggested that once daily dosing was associated with an approximately 20% increase in adherence. This significant difference persisted among subgroups defined by sex, race/ethnicity, age, and asthma severity.

CONCLUSION

Once daily dosing was associated with higher adherence to ICS therapy; this included clinically relevant subgroups.

A meta-analysis identifies new loci associated with body mass index in individuals of African ancestry

Genome-wide association studies (GWAS) have identified 36 loci associated with body mass index (BMI), predominantly in populations of European ancestry. We conducted a meta-analysis to examine the association of >3.2 million SNPs with BMI in 39,144 men and women of African ancestry and followed up the most significant associations in an additional 32,268 individuals of African ancestry. We identified one new locus at 5q33 (GALNT10, rs7708584, P = 3.4 × 10(-11)) and another at 7p15 when we included data from the GIANT consortium (MIR148A-NFE2L3, rs10261878, P = 1.2 × 10(-10)). We also found suggestive evidence of an association at a third locus at 6q16 in the African-ancestry sample (KLHL32, rs974417, P = 6.9 × 10(-8)). Thirty-two of the 36 previously established BMI variants showed directionally consistent effect estimates in our GWAS (binomial P = 9.7 × 10(-7)), five of which reached genome-wide significance. These findings provide strong support for shared BMI loci across populations, as well as for the utility of studying ancestrally diverse populations.

Effect of ezetimibe on major atherosclerotic disease events and all-cause mortality

Despite ezetimibe's ability to reduce serum cholesterol levels, there are concerns over its vascular effects and whether it prevents or ameliorates atherosclerotic disease (AD). The aims of this study were to estimate the effect of ezetimibe use on major AD events and all-cause mortality and to compare these associations to those observed for hydroxymethylglutaryl coenzyme A reductase inhibitor (statin) use. A total of 367 new ezetimibe users were identified from November 1, 2002, to December 31, 2009. These subjects were aged ≥18 years and had no previous statin use. One to 4 statin user matches were identified for each ezetimibe user, resulting in a total of 1,238 closely matched statin users. Pharmacy data and drug dosage information were used to estimate a moving window of ezetimibe and statin exposure for each day of study follow-up. The primary outcome was a composite of major AD events (coronary heart disease, cerebrovascular disease, and peripheral vascular disease events) and all-cause death. Ezetimibe use (odds ratio 0.33, 95% confidence interval 0.13 to 0.86) and statin use (odds ratio 0.61, 95% confidence interval 0.36 to 1.04) were associated with reductions in the likelihood of the composite outcome. These protective associations were most significant for cerebrovascular disease events and all-cause death. Subgroup analyses by gender, race or ethnicity, history of AD, diabetes status, and estimated renal function showed consistent estimates across strata, with no significant differences between ezetimibe and statin use. In conclusion, ezetimibe appeared to have a protective effect on major AD events and all-cause death that was not significantly different from that observed for statin use.

Integration of mouse and human genome-wide association data identifies KCNIP4 as an asthma gene

Asthma is a common chronic respiratory disease characterized by airway hyperresponsiveness (AHR). The genetics of asthma have been widely studied in mouse and human, and homologous genomic regions have been associated with mouse AHR and human asthma-related phenotypes. Our goal was to identify asthma-related genes by integrating AHR associations in mouse with human genome-wide association study (GWAS) data. We used Efficient Mixed Model Association (EMMA) analysis to conduct a GWAS of baseline AHR measures from males and females of 31 mouse strains. Genes near or containing SNPs with EMMA p-values <0.001 were selected for further study in human GWAS. The results of the previously reported EVE consortium asthma GWAS meta-analysis consisting of 12,958 diverse North American subjects from 9 study centers were used to select a subset of homologous genes with evidence of association with asthma in humans. Following validation attempts in three human asthma GWAS (i.e., Sepracor/LOCCS/LODO/Illumina, GABRIEL, DAG) and two human AHR GWAS (i.e., SHARP, DAG), the Kv channel interacting protein 4 (KCNIP4) gene was identified as nominally associated with both asthma and AHR at a gene- and SNP-level. In EVE, the smallest KCNIP4 association was at rs6833065 (P-value 2.9e-04), while the strongest associations for Sepracor/LOCCS/LODO/Illumina, GABRIEL, DAG were 1.5e-03, 1.0e-03, 3.1e-03 at rs7664617, rs4697177, rs4696975, respectively. At a SNP level, the strongest association across all asthma GWAS was at rs4697177 (P-value 1.1e-04). The smallest P-values for association with AHR were 2.3e-03 at rs11947661 in SHARP and 2.1e-03 at rs402802 in DAG. Functional studies are required to validate the potential involvement of KCNIP4 in modulating asthma susceptibility and/or AHR. Our results suggest that a useful approach to identify genes associated with human asthma is to leverage mouse AHR association data.

Asthma medication adherence: the role of God and other health locus of control factors

BACKGROUND

Medication adherence is an important determinant of disease outcomes, yet medication use on average tends to be low among patients with chronic conditions, including asthma. Although several predictors of non-adherence have been assessed, more research is needed on patients' beliefs about God and how these relate to medication use.

OBJECTIVE

To examine the relationship between perceptions about "God's" role in health and other locus of control factors with inhaled corticosteroid (ICS) adherence among asthma patients.

METHODS

Participants were from a clinical trial to improve ICS adherence and were 5-56 years old, had a diagnosis of asthma, and were receiving ICS medication. Baseline adherence was estimated from electronic prescription and pharmacy fill records. Patients were considered to be adherent if ICS use was ≥80% of prescribed. A baseline survey with the Multidimensional Health Locus of Control scale was used to assess five sources (God, doctors, other people, chance, and internal).

RESULTS

Medication adherence was low (36%). Patients' who had a stronger belief that God determined asthma control were less likely to be adherent (odds ratio [OR] 0.82, 95% confidence interval [CI] 0.70-0.96). This relationship was stronger among African American (OR 0.68, 95% CI0.47-0.99) compared to white patients (OR 0.89, 95% CI 0.75-1.04), and among adults (OR 0.81, 95% CI 0.69-0.96) compared to children (OR 0.84, 95% CI 0.58-1.22).

CONCLUSION

Patients' belief in God's control of health appears to be a factor in asthma controller use, and therefore should be considered in physician-patient discussions concerning course of treatment.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00459368.

A meta-analysis of genome-wide association studies for serum total IgE in diverse study populations

BACKGROUND

IgE is both a marker and mediator of allergic inflammation. Despite reported differences in serum total IgE levels by race-ethnicity, African American and Latino subjects have not been well represented in genetic studies of total IgE.

OBJECTIVE

We sought to identify the genetic predictors of serum total IgE levels.

METHODS

We used genome-wide association data from 4292 subjects (2469 African Americans, 1564 European Americans, and 259 Latinos) in the EVE Asthma Genetics Consortium. Tests for association were performed within each cohort by race-ethnic group (ie, African American, Latino, and European American) and asthma status. The resulting P values were meta-analyzed, accounting for sample size and direction of effect. Top single nucleotide polymorphism associations from the meta-analysis were reassessed in 6 additional cohorts comprising 5767 subjects.

RESULTS

We identified 10 unique regions in which the combined association statistic was associated with total serum IgE levels (P<5.0×10(-6)) and the minor allele frequency was 5% or greater in 2 or more population groups. Variant rs9469220, corresponding to HLA-DQB1, was the single nucleotide polymorphism most significantly associated with serum total IgE levels when assessed in both the replication cohorts and the discovery and replication sets combined (P=.007 and 2.45×10(-7), respectively). In addition, findings from earlier genome-wide association studies were also validated in the current meta-analysis.

CONCLUSION

This meta-analysis independently identified a variant near HLA-DQB1 as a predictor of total serum IgE levels in multiple race-ethnic groups. This study also extends and confirms the findings of earlier genome-wide association analyses in African American and Latino subjects.

Genetic ancestry and its association with asthma exacerbations among African American subjects with asthma

BACKGROUND

There are large and persisting disparities in severe asthma exacerbations by race-ethnicity, and African American subjects are among those at greatest risk. It is unclear whether this increased risk solely represents differences in environmental exposures and health care or whether there is a predisposing genetic component.

OBJECTIVE

We sought to assess the relationship between genetic ancestry and severe exacerbations among African American subjects with asthma.

METHODS

Participants were part of the Study of Asthma Phenotypes and Pharmacogenomic Interactions by Race-ethnicity (SAPPHIRE). These subjects were 12 to 56 years of age, received care from a single large health system, and had a physician's diagnosis of asthma. Genetic ancestry was estimated by using a set of validated ancestry informative markers. Severe exacerbations (ie, asthma-related emergency department visits, hospitalizations, and burst oral steroid use) were prospectively identified from health care claims.

RESULTS

We assessed genetic ancestry in 392 African American subjects with asthma. The average proportion of African ancestry was 76.1%. A significant interaction was identified between ancestry and sex on severe exacerbations, such that the risk was significantly higher with increasing African ancestry among male but not female subjects. The association among male subjects persisted after adjusting for potential confounders (relative rate, 4.30 for every 20% increase in African ancestry; P = .029).

CONCLUSIONS

African ancestry was significantly and positively associated with severe exacerbations among male African American subjects. These findings suggest that a portion of the risk of asthma exacerbations in this high-risk group is attributable to a genetic risk factor that partitions with ancestry.

Further replication studies of the EVE Consortium meta-analysis identifies 2 asthma risk loci in European Americans

BACKGROUND

Genome-wide association studies of asthma have implicated many genetic risk factors, with well-replicated associations at approximately 10 loci that account for only a small proportion of the genetic risk.

OBJECTIVES

We aimed to identify additional asthma risk loci by performing an extensive replication study of the results from the EVE Consortium meta-analysis.

METHODS

We selected 3186 single nucleotide polymorphisms for replication based on the P values from the EVE Consortium meta-analysis. These single nucleotide polymorphisms were genotyped in ethnically diverse replication samples from 9 different studies, totaling 7202 cases, 6426 controls, and 507 case-parent trios. Association analyses were conducted within each participating study, and the resulting test statistics were combined in a meta-analysis.

RESULTS

Two novel associations were replicated in European Americans: rs1061477 in the KLK3 gene on chromosome 19 (combined odds ratio = 1.18; 95% CI, 1.10-1.25) and rs9570077 (combined odds ratio =1.20; 95% CI, 1.12-1.29) on chromosome 13q21. We could not replicate any additional associations in the African Americans or Latinos.

CONCLUSIONS

This extended replication study identified 2 additional asthma risk loci in populations of European descent. The absence of additional loci for African Americans and Latinos highlights the difficulty in replicating associations in admixed populations.

Comparison of renal predictors for in-hospital and postdischarge mortality after hospitalized heart failure

OBJECTIVES

Abnormal baseline and acutely worsening renal function (WRF) during heart failure hospitalization are associated with worse outcomes. However, which renal criterion is most predictive of in-hospital and postdischarge mortality is uncertain.

METHODS

We analyzed patients hospitalized for heart failure between 1 January 2000 and 30 June 2008. Preexisting end-stage renal disease was excluded. Blood urea nitrogen (BUN), creatinine, and modification of diet in renal disease-estimated glomerular filtration rate (eGFR) at admission and during hospitalization were tested for association with in-hospital and 1-year mortality. Logistic regression and conditional receiver operating curves were used to compare criteria in terms of association with mortality.

RESULTS

Among 7394 patients, 204 died in-hospital and 1652 within 1 year. Admission BUN was the strongest correlate for both in-hospital and postdischarge mortality [area under the curve (AUC) = 0.724 and 0.656; P < 0.001 vs. creatinine/eGFR], showing 4.6-fold and 3.0-fold mortality, respectively. Adjusting for baseline BUN, subsequent changes in creatinine and BUN performed similarly for in-hospital death (model AUC 0.812; P < 0.001 vs. eGFR) and postdischarge death (all similar, model AUC = 0.661). Optimally predictive thresholds of WRF in hospital were dependent on the baseline renal function and did not always correspond to common definitions.

CONCLUSION

Among hospitalized heart failure patients, baseline BUN is the renal index most strongly associated with in-hospital and 1-year mortality. WRF definitions that use BUN or creatinine have similar discriminative ability overall, but commonly used thresholds are suboptimal for predicting mortality; optimal thresholds varied with baseline renal function and time horizon.