DNAprint Genomics (DNAG)

[mingwan0]

HGM2004 Human Genome Meeting
Berlin, Germany
4th - 7th April 2004

http://hgm2004.hgu.mrc.ac.uk/Abstracts/Publish/WorkshopPosters/WorkshopPosters04/hgm075.html

HGM2004 Poster Abstracts
4. Complex Disorders

Poster 75

Population Stratification Confounds Asthma Studies Among Latino Americans

1S. Choudhry, 1N.E. Coyle, 1D. Lind, 2H. Tang, 1K. Salari, 1S.L. Clark, 1N. Ung, 1H. Matallana, 1P.C. Avila, 3J. Casal, 3A. Torres, 3S. Nazario, 1M. Toscano, 1R. Castro, 3W. Rodriguez-Cintron, 1Pui-Yan Kwok, 1D. Sheppard, 4M.D. Shriver, 5,6N. Risch, 1E. Ziv, 1E.G. Burchard

1University of California, San Francisco, San Francisco, CA, USA, 2Fred Hutchinson Cancer Research Center, Seattle, WA, USA, 3University of Puerto Rico, San Juan, PR, 4Pennsylvania State University, College Station, PA, USA, 5Stanford University, Stanford, CA, USA, 6Kaiser Department of Research, Oakland, CA, USA

Purpose: Case-control association studies are a powerful strategy for identifying genes of modest effect in complex diseases such as asthma. However, such studies may be confounded in racially admixed populations, such as Latinos. We tested whether population stratification may affect the results of asthma case-control studies in Puerto Ricans and Mexican Americans.

Methods: Mexican American asthmatic probands and ethnically matched controls (360) recruited from the San Francisco Bay Area and Puerto Rican asthmatic probands and matched controls (360) recruited from Puerto Rico were typed for 52 ancestry informative markers (AIMs). These AIMs were selected for their high allele frequency differences between West Africans, Europeans and Native Americans. For each population we tested whether the degree of association between pairs of markers on different chromosomes was greater than expected using a permutation test. Population stratification was assessed by comparing the global differences in allele frequencies between cases and controls.

Results: Among Puerto Ricans, the association between markers on different chromosomes was significantly greater than expected (p<0.0001). Among Mexicans, there was a non-significant trend towards association between markers on different chromosomes (p=0.07). Among Puerto Ricans, 9 of 52 markers were significantly associated with asthma, and there was a significant difference between cases and controls (p=0.00031). Among Mexican Americans, 3 of 52 markers were associated with asthma and there was no significant difference between cases and controls (p=0.44).

Conclusion: Case-control genetic association studies of asthma are susceptible to genetic confounding in Latino populations. Empirical assessment of the effects of stratification will be important to appropriately interpret the results of case-control studies.