Which change would increase Relative Risk for disease Y associated with HLA allele X?

The concept of Relative Risk (RR) is crucial in assessing the strength of an association between an exposure (in this case, possessing HLA allele X) and an outcome (the occurrence of disease Y). Relative Risk is calculated based on the proportion of individuals with the exposure who develop the disease compared to those without the exposure.

When considering the impact of changes on Relative Risk, having fewer controls with HLA type X in the sampled population increases the likelihood that the allele is associated with the disease. This is because a decrease in controls with the HLA type X allele means that the comparison group for assessing the risk will be less representative. If fewer controls carry the allele, the proportion of patients with the disease who have the allele may appear higher, leading to a greater calculated relative risk for disease Y associated with allele X.

This shift in ratios increases the appearance of a relationship between having HLA type X and developing disease Y. The underlying biological implications could suggest a stronger influence of HLA type X on the risk of the disease, which would be reflected in an increased Relative Risk (RR). By reducing the number of controls with the allele, the odds appear more favorable to support the hypothesis of a significant association, thereby enhancing the calculated RR.

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