Association study using combination analysis of SNP and STRP markers: CD14 promoter polymorphism and IgE level in Taiwanese asthma children.

Chromosome 5, especially the 5q31-33 region, may contain one or more loci to control total serum IgE as well as asthma and bronchial hyperresponsiveness. To investigate the regions related with IgE level in chromosome 5, we performed a case-control association study on 105 high-IgE-level and 85 normal-IgE-level asthmatic children using 43 microsatellite markers that span the whole chromosome 5 with 5 cM intervals. One of microsatellite marker, D5S2011, had significantly different allele frequency between the two asthmatic groups. E allele (143 bp) of the D5S2011 marker was more frequent in high-IgE asthmatics. CD14 is the candidate gene of atopy and asthma and is distant from D5S2011 by about 1 Mb. We analyzed the SNP genotypes in the CD14 gene region alone and in combination with microsatellite marker D5S2011. The CD14/-2984 polymorphism but not the CD14/-159 is associated with IgE level in Taiwanese asthmatic children. The CD14/-159 allele was observed only to be associated with IgE level when -159T was part of a haplotype containing a D5S2011 E allele. The combination analysis using SNP and STRP markers provided a novel method for increasing detection power in candidate gene association studies.