The Reporting Odds Ratio (ROR) is a disproportionality measure commonly used by drug safety professionals to help identify drug-associated adverse events (AEs) that are reported more frequently than expected. In broad terms, ROR is derived by comparing two ratios: 1) The number of cases of a particular AE reported for a particular drug / # of all other AE cases for that particular drug, to 2) The number of cases of that particular AE across all other drugs / # of all other AE cases across all other drugs in our database.
If the pairing of a given drug and a given AE occurs with average frequency as that seen across all drugs on our database, the ROR would equal 1.0.
A ROR score of ≥1.0 indicates that there is a higher than average reporting rate for a given AE / drug combination. While there is no widely accepted benchmark regarding the numerical level at which disproportionality analysis yields a “safety signal,” we generally believe ROR’s of ≥2.0 warrant extra attention. We use ROR as part of our signaling system in our predictive analytic RxSignal.
We derive ROR by the use of a standard formula:
Variables:
a = the number of primary case reports involving Drug X and Adverse Event Y;
b = the number of primary case reports involving Drug X and NOT Adverse Event Y;
c = the number of primary case reports involving NOT Drug X and Adverse Event Y;
d = the number of primary case reports involving NOT Drug X and NOT Adverse Event Y.
Example
a = 4 cases of nausea reported for Invokana (sitagliptin) b = 50 cases of all other adverse events reported for Invokana (sitagliptin) c = 100 cases of nausea reported across all other drugs in Evidex d = 1000 cases of all other adverse events reported across all other drugs in Evidex
ROR = (a/b)/(c/d) = (4/50)/(100/1000) = .08/.10 = .80