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The major histocompatibility complex (MHC) has been linked with hundreds of diseases [1]. The MHC is one of the most complex regions of the human genome, because of the high gene density, extended linkage disequilibrium (LD) and sequence diversity [2]. Recent genome-wide association studies (GWAS) have identified polymorphisms located in the MHC that are associated with lung diseases and related traits: asthma, cystic fibrosis, idiopathic interstitial pneumonia, lung cancer and lung function. However, due to the limitations of GWAS and tissue-specific characteristics of gene expression [3], the causal genes and genetic mechanisms mediating the heritable risk within this locus remain to be found.

To the Editor: A number of models have been proposed to predict spirometric lung function using age, sex, height and self-reported ethnicity [1, 2]. These models are particularly important to derive per cent predicted lung function and establish the severity of lung diseases such as chronic obstructive pulmonary disease (COPD) [3]. Compared to self-reported race and/or ethnicity, genetic data can provide more accurate and objective measurements of ancestry and has the potential to alleviate some of the problems related to the lack of consensus on the definition of race and ethnicity worldwide [4]. A recent report suggested that genetically determined ancestry improves predicted lung-function measurements in African Americans [5]. Here, we test whether genetic ancestry derived from genome-wide genotyping data is useful to predict lung function in a diverse European population. The population used in this study is part of a lung expression quantitative trait loci (eQTL) mapping study [6, 7]. Briefly, research participants were recruited from three academic sites: Laval University (Quebec, QC, Canada), University of British Columbia (Vancouver, BC, Canada), and Groningen University (Groningen, the Netherlands), henceforth referred to as Laval, UBC, and Groningen, respectively. All subjects were genotyped for ∼1.2 million single nucleotide polymorphisms (SNPs) using the Illumina Human1M-Duo BeadChip (Illumina, Inc., San Diego, CA, USA). Subjects from Laval and UBC provided written informed consent and the study was approved by the ethics committees of the respective study sites. At Groningen, the study protocol was consistent with the research code of the University Medical Center Groningen and Dutch national ethical and professional guidelines (“Code of conduct; Dutch federation of biomedical scientific societies”; http://www.federa.org). Prior to the analysis, standard genotyping quality controls and exclusion of patients with disorders that affected lung function (other than COPD) were …