Information Component computations
When you specify data mining parameters for an MGPS run, you can include Information Component (IC) computations.
The IC is a measure of disproportionality between the observed and expected number of reports for a drug-event combination. A positive IC indicates that the number of observed reports is greater than the number of expected reports. Similarly, a negative IC indicates that the number of observed reports is less than the number of expected reports.
Oracle Empirica Signal computes IC values only for drug-event combinations. For example, if you create a three-dimensional MGPS run, Oracle Empirica Signal computes IC values for each drug-event combination, and disregards the following:
- Combinations of one drug and two events.
- Combinations of two drugs and one event.
- Combinations of three drugs.
- Combinations of three events.
IC values include the following:
- IC—Information component
- IC025—Lower limit of the 95 percent confidence interval for IC
- IC975—Upper limit of the 95 percent confidence interval for IC
If you selected stratification variables for the run, the expected number of reports (E) is adjusted using the Mantel-Haenszel approach. For more information, see Stratification variables.
If you defined a subset variable for the run, Oracle Empirica Signal computes results for each value of the subset variable with observed cases in the data.
Drug-event combination scores
- Oracle Empirica Signal determines the observed counts for each drug-event combination as follows:
Event Drug of interest All other drugs Event of interest
a
b
All other events
c
d
- a—Number of reports of the drug of interest and the event of interest.
- b—Number of reports of the event of interest and not the drug of interest.
- c—Number of reports of the drug of interest and not the event of interest.
- d—Number of reports of neither the event or drug of interest.
- Oracle Empirica Signal computes the expected counts for each drug-event combinations as follows:
Event Drug of interest All other drugs Event of interest
E(a)=((a+b)(a+c))/(a+b+c+d)
E(b)=((a+b)(b+d))/(a+b+c+d)
All other events
E(c)=((c+d)(a+c))/(a+b+c+d)
E(d)=((c+d)(b+d))/(a+b+c+d)
Note:
If you specify a stratification variable for the run, Oracle Empirica Signal adjusts the expected count (E) using the Mantel-Haenszel approach. - Oracle Empirica Signal computes the IC and IC confidence interval for each drug-event combination as
follows:
IC = log2 ((O + α1) / (E + α2))
IC025 = log2 ((O + α1) / (E + α2)) - 3.3 * (O + α1)-1/2 - 2 * (O+ α1)-3/2
IC975 = log2 ((O + α1) / (E + α2)) + 2.4 * (O + α1)-1/2 - .5 * (O+ α1)-3/2
where:
α1=α2= 1/2
O is the observed count.
E is the expected count.
Parent topic: Reference