CDC antibiotic-use reporting · metric explainer
Days of therapy counts calendar days on which a patient receives a specific antimicrobial agent. It is a utilization measure, not a stand-alone grade for the quality of a hospital, unit or prescriber.
What days of therapy measures
In the Centers for Disease Control and Prevention National Healthcare Safety Network Antimicrobial Use Option, facilities submit antimicrobial-use data for defined patient-care locations and time periods. A day of therapy, often shortened to DOT, is attributed when a patient receives one or more doses of an antimicrobial agent on a calendar day.
Two agents administered to one patient on the same day contribute two agent-level days of therapy. Multiple doses of the same agent on that day do not create additional days for that agent. The measure therefore describes exposure days rather than dose amount, clinical indication or whether treatment was correct.
Why the denominator matters
A raw DOT count grows with patient volume and time. Interpretation requires the reporting location, month, eligible agents and a denominator such as days present, following the current NHSN protocol. An adult intensive-care unit, pediatric ward and outpatient setting should not be treated as interchangeable populations.
DOT can show how much antimicrobial exposure was reported. It cannot, by itself, show why a drug was used, whether the diagnosis was correct, whether a shorter course was appropriate or whether one facility delivered better care.
What a fair comparison needs
- The same antimicrobial-agent grouping and reporting period.
- Comparable patient-care locations and denominator definitions.
- Complete, validated submissions under the same protocol version.
- Clinical context, case mix and a documented stewardship question.
What readers can verify next
Ask which NHSN option, location, denominator and data-quality checks produced the value. If a report presents a ranking, look for its adjustment method and uncertainty. DOT should support a stewardship investigation, not direct an individual to start, stop or change an antibiotic.