DISCUSSION
In this study, we developed a preliminary QTc-prolongation risk score
with a sensitivity of 81%, a specificity of 35%, a PPV of 32%, and an
NPV of 84%. Compared with the DDI warnings, our full dataset achieved
better sensitivity and NPV, but that resulted in less specificity and
PPV. Our multiple logistic regressions allowed us to achieve a
sensitivity of 68%, specificity of 66%, a PPV of 45% and an NPV of
83% with an optimized risk score and a cutoff of 5 points. Our aim of
reducing false positive alerts by 20% was not achieved, however, many
of the DDI warnings were filtered, and those that actually triggered and
were included in our calculations were mostly severe, with a high risk
of QTc prolongation. On the contrary, medications triggering our risk
score calculation and custom alert were based on lists 1, 2 and 3 of
CredibleMeds, making it easier to achieve a greater number of custom
alerts than DDI warnings. In addition, DDI warnings were only identified
in patients who already had the risk score calculated and a custom alert
generated. Vandael and colleagues included patients from various
hospitals and wards including cardiology, internal medicine and
others.4 Patients at our institution, however, were
all cancer patients with different characteristics and risk factors
affected by various therapies and comorbidities. Moreover, the study by
Vandael and colleagues did not compare the risk score to any existing
warning, unlike our study which compared the risk score to an existing
DDI warning, aiming to reduce alert burden and fatigue. The study by
Tisdale and colleagues included only patients on cardiac units, and did
not compare the risk score to another existing warning. However, it had
a pre and a post-implementation phase which revealed that incorporating
a validated risk score influenced the prescribing of noncardiac QTc
interval-prolonging drugs and reduced the risk of
QTc-prolongation.6