Denominator Exceptions
A denominator exception allows the measured entity to get credit when the measured entity performs the quality action, but not penalized if not done for an appropriate reason. The exception allows the exercise of clinical judgment and implies the measured entity considered or offered treatment to each potentially eligible patient in the denominator. Denominator exceptions are most appropriate when measures of contraindications to drugs or procedures are relative (Spertus et al., 2010). A measure developer should specifically define a denominator exception when capturing the information in a structured manner fitting the clinical workflow. The measure developer should only use a denominator exception in proportion measures. It is not appropriate for ratio or continuous variable measures.
Although no single agreed-upon approach to denominator exceptions exists, there seems to be consensus that denominator exceptions provide valuable information for clinical decision-making. Measure developers who build denominator exceptions into measure logic should be aware that—once implemented— denominator exception rates may be subject to reporting, auditing, endorsement/maintenance review, and validation of appropriateness. The measure developer should account for these factors in measure design and development.
Reasons for Denominator Exceptions | Description | Examples |
|---|---|---|
Medical Reasons | Medical reasons should be precisely defined and evidence-based. The events excepted should occur often enough to distort measure results if not accounted for. A broadly defined medical reason such as “any reason documented by physician” may create an uneven comparison if some physicians have reasons that may not be evidence-based. | Medication specified in the numerator is known to cause harm to fetuses, and there is documentation the patient’s pregnancy is the reason for not prescribing an indicated medication. If in the course of a measure’s use, the measure developer finds that medical reasons resulting in a denominator exception occur in a high enough volume and are of universal applicability, then the measure developer can consider the denominator exception for redefinition as a denominator exclusion. Asthma is an allowable denominator exception for the quality measure of the use of beta blockers for patients with heart failure. Thus, physician judgment may determine there is greater benefit for the patient to receive beta blockers for heart failure than the risk of a problem occurring due to the patient’s coexisting condition of asthma. If the measured entity gives the medication, the measure implementer does not search for denominator exceptions, and the patient remains in the denominator. If the measured entity did not give the medication, the implementer looks for relevant denominator exceptions and removes the patient−in this example, a patient with asthma−from the denominator. If the measured entity did not give the medication and the patient does not have any denominator exceptions, the patient remains in the denominator and the measured entity fails the measure. |
Patient Reasons | Patient reasons for not receiving the service specified may be a denominator exception to allow for patient preferences. | The patient has a religious conviction precluding the patient from receiving the specific treatment, the physician explained the benefits of the treatment, and documented the patient’s refusal in the record. |
System Reasons | System reasons are generally rare. The measure developer should limit these to identifiable situations that are known to occur. | A vaccine shortage prevented administration of the vaccine. |
The measure developer must capture the denominator exception with explicitly defined data elements that allow analysis of the denominator exception across measured entities to identify patterns of inappropriate denominator exception and gaming and to detect potential health care disparity issues. Analysis of rates without attention to denominator exception information has the potential to mask disparities in health care and differences in measured entity performance.
Transparency and Evidence
To ensure transparency, the measure developer should capture an allowable denominator exception in a way the measured entity can report it separately, in addition to the overall measure rate. The measure developer should support an allowable denominator exception with evidence
- Of sufficient frequency of occurrence such that distortion of the measure results occurs without the denominator exception
- The denominator exception is clinically appropriate to the eligible population for the measure
Although no single agreed-upon approach to denominator exceptions exists, there seems to be consensus that denominator exceptions provide valuable information for clinical decision-making. Measure developers who build denominator exceptions into measure logic should take caution that, once implemented, denominator exception rates may be subject to reporting, auditing, endorsement/maintenance review, and validation of appropriateness. The measure developer should account for these factors in measure design and development.
- Examples
- Inappropriate denominator exception: a notation in the patient’s medical record indicates a reason for not performing the specified care, and scientific evidence does not support the reason.
- Gaming: patient refusal may be a denominator exception; however, it has the potential for overuse. For example, a measured entity does not actively encourage the service, explain its advantages, or attempt to persuade the patient, and then uses patient refusal as the reason for nonperformance.
- Disparity issues: the use of a patient reason for denominator exception for mammograms is found to be high for a minority population, which may indicate a need for more targeted, culturally appropriate patient education or closer examination of patient access issues such as lack of transportation or lack of childcare.