Table 5. Calculation of an alert performance measure.
| Patient clinical condition | Performance measures | |||
|---|---|---|---|---|
| Condition present | Condition absent | |||
| Alert behavior | Condition criteria triggered (alert fired) |
(A) True positive: condition identified | (B) False positive: condition incorrectly identified | Positive predictive value: A/(A + B) b c |
| Condition criteria not triggered (no alert) |
C) False negative: condition missed | (D) True negative: condition truly absent and alert correctly did not fire | Negative predictive value: D/(C + D) b | |
| Performance measures | Sensitivity: A/(A + C) a | Specificity: D/(B + D) a | ||
a
Not affected by condition prevalence.
b
Affected by condition prevalence.
c
Easiest to calculate since both numerator and denominator are based on easily retrieved alert firing data. All other performance measures have either true or false negatives, both of which require methods like manual chart review or retrospective query of validated cohort criteria to calculate.