title: Comparing Analytic Methods for Longitudinal GWAS and a Case-Study Evaluating Chemotherapy Course Length in Pediatric AML. A Report from the Children's Oncology Group.
abstract: Regression analysis is commonly used in genome-wide association studies (GWAS) to test genotype-phenotype associations but restricts the phenotype to a single observation for each individual. There is an increasing need for analytic methods for longitudinally collected phenotype data. Several methods have been proposed to perform longitudinal GWAS for family-based studies but few methods are described for unrelated populations. We compared the performance of three statistical approaches for longitudinal GWAS in unrelated subjectes: (1) principal component-based generalized estimating equations (PC-GEE); (2) principal component-based linear mixed effects model (PC-LMEM); (3) kinship coefficient matrix-based linear mixed effects model (KIN-LMEM), in a study of single-nucleotide polymorphisms (SNPs) on the duration of 4 courses of chemotherapy in 624 unrelated children with de novo acute myeloid leukemia (AML) genotyped on the Illumina 2.5 M OmniQuad from the COG studies AAML0531 and AAML1031. In this study we observed an exaggerated type I error with PC-GEE in SNPs with minor allele frequencies < 0.05, wheras KIN-LMEM produces more than expected type II errors. PC-MEM showed balanced type I and type II errors for the observed vs. expected P-values in comparison to competing approaches. In general, a strong concordance was observed between the P-values with the different approaches, in particular among P < 0.01 where the between-method AUCs exceed 99%. PC-LMEM accounts for genetic relatedness and correlations among repeated phenotype measures, shows minimal genome-wide inflation of type I errors, and yields high power. We therefore recommend PC-LMEM as a robust analytic approach for GWAS of longitudinal data in unrelated populations.
authors.affiliation: Division of Oncology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Marijana
authors.initials: M
authors.lastname: Vujkovic
authors.affiliation: Division of Oncology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Aplenc
authors.affiliation: Department of Preventive Medicine, Keck School of Medicine, University of Southern California Los Angeles, CA, USA.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Alonzo
authors.affiliation: Division of Hematology, Oncology Bone Marrow Transplantation, Children's Mercy Hospitals and Clinics Kansas City, MO, USA.
authors.forename: Alan S
authors.initials: AS
authors.lastname: Gamis
authors.affiliation: Division of Oncology, Children's Hospital of Philadelphia Philadelphia, PA, USA.
authors.forename: Yimei
authors.initials: Y
authors.lastname: Li
keywords: generalized estimating equations; genome wide association analysis; linear mixed effects model; longitudinal analysis; unrelated population