ADE Prevention and Monitoring: Warfarin Time in Therapeutic Range

Last updated: May 3, 2018

CMS Measure ID: CMS179v4
Version: 4
NQF Number: None
Measure Description:

Average percentage of time in which patients aged 18 and older with atrial fibrillation who are on chronic warfarin therapy have International Normalized Ratio (INR) test results within the therapeutic range (i.e., TTR) during the measurement period.

Initial Patient Population:

Patients aged 18 and older with atrial fibrillation without valvular heart disease who had been on chronic warfarin therapy for at least 180 days before the start of and during the measurement period. Patient should have at least one outpatient visit during the measurement period

Measure Population:

Equals All in Initial Population with sufficient international normalized ratio (INR) results to calculate a warfarin time in therapeutic range (TTR)

Measure Observations:

Average percentage of time that patients in the measure population have INR results within the therapeutic range (i.e., TTR)

Denominator Statement:

Not Applicable

Denominator Exclusions:

Not Applicable

Numerator Statement:

Not Applicable

Numerator Exclusions:

Not Applicable

Denominator Exceptions:

Not Applicable

Measure Steward: Centers for Medicare and Medicaid Services
Domain: Patient Safety
Next Version:
Previous Version:
Measure Score: Continuous Variable
Improvement Notation:

A higher score indicates higher quality


Please note that the logic expressions in the body section of the HQMF of this measure should not be used to calculate this clinical quality measure. They are only provided to represent the data elements needed for the calculation. In order to calculate this clinical quality measure correctly, only use the narrative specifications contained in the header section of the HQMF and the annotated database query found in the supplemental file named CMS179v4_Supplemental_SQL_Logic_Reference.pdf.

The calculation of TTR should include all available INR values for a given patient during the measurement period. When generating a QRDA-1 document for this measure, all available INR values during the measurement period should be included.

The following filters are applied to each patient's INRs in order to calculate a patient-level TTR. INR values must be at least 0.8. Values less than 0.8 may represent aberrant results. INR values greater than 10 (i.e., outliers) must be replaced with a value of 10. An INR of 10 represents an abnormally high INR and would skew the results of the calculated TTR less than extreme values would (i.e., INR > 10). The INR value closest to 2.5 is used to calculate TTR, when there are more than one INR result on a single date.

In this measure, the active drug ingredient of primary interest is warfarin. CUMULATIVE MEDICATION DURATION should be calculated for all active warfarin-containing medications. All of the entries in the value set for warfarin must be included when determining the cumulative medication duration. All medication occurrences considered for the calculation of cumulative medication duration for this measure must be active within 200 days immediately prior to the measurement period. This lookback period of 200 days is based on the original warfarin TTR measure used by the Veterans Affairs health care system. Please refer to the supplemental file named CMS179v4 _Supplemental_SQL_Logic_Reference.pdf for this logic.

To be excluded from the initial patient population, patients must have an active diagnosis of valvular heart disease during the measurement period.

To determine the proportion of patients with atrial fibrillation who are on chronic warfarin therapy and have sufficient INR monitoring to calculate a TTR, the reporting provider can divide the Measure Population by the Initial Patient Population.

The calculation for TTR is provided in the supplemental file named CMS179v4 _Supplemental_SQL_Logic_Reference.pdf.

The Measure Observation is the average of all patients' percent TTR, which can be calculated by dividing the sum of all patients' percent TTR by the number of patients in the Measure Population.


Release Notes


  • Copyright updated.
  • Disclaimer updated.
  • eMeasure version number incremented.


  • Changed data type of 'result' or 'finding' to 'performed'.
  • Introduced logic to capture Sum >= 180 days(s) of: 'Medication, Active: Warfarin' with attribute cumulative medication duration to calculate cumulative medication duration.
  • Introduced 'satisfies all' clause to replace previously used AND and AND NOT logical operators and to streamline expression logic.
  • Introduced the new timing operator 'overlaps' to replace two lines of logic (AND/AND NOT) or to enforce when an event or set of events occur to meet the measure intent.
  • Removed extraneous AND from Initial Population.
  • Replaced 'ORs' with 'Union of' operator to provide a mechanism for specifying that qualifying event(s) must be a member of at least one of the data elements being unioned (if appropriate for measure intent).
  • Replaced 'Patient Characteristic Birthdate' with 'Age at' operator.

Value Sets

No changes

External Resources