Issues and Future Directions

Power calculations assumed that there are two controls for each case and a SNP that operates as if it was a simple binary factor to which a proportion of the population are exposed in a manner directly related to the genotypic frequency (e.g., for 19% exposure, equivalent to a dominant allele at Hardy-Weinberg equilibrium with a prevalence of 10%). 

Both mode of inheritance (dominant, recessive) and allele frequency can have dramatic effects on required sample sizes (Table 10.2). Even for the best case scenario - a common SNP acting in a dominant fashion - a relatively large sample size of more than 300 cases (a total sample size of 900 subjects) is required at an a of 0.05 (Table 10.2). 

This work was supported in part by grant 5 U01 HL65899-02 from the National Heart, Lung and Blood Institute of the NIH. 

1 Asher MI, Keil U, Anderson HR et al. International Study of asthma and allergies in childhood (ISAAC) rationale and methods. Eur Respir J 1995 8 483-491. 

2 Lenney W. The burden of pediatric asthma. Pediatr Pulmonol Suppl 1997 15 13-16. 

---