Synonyms: Ratio estimate
Causal estimate obtained for a single instrumental variable (IV) by dividing the beta coefficient describing the association between the genetic variant being used as an IV and the outcome by the beta coefficient describing the association between the genetic variant and the exposure.
To estimate a valid causal effect, genetic variants must satisfy the MR assumptions. The Wald ratio is equivalent to the two-stage least squares (TSLS) method where the exposure is associated with one IV.