Value-based care tools
Medication adherence (PDC) calculator
Paste or upload a pharmacy fill history to get proportion of days covered per drug and for the three Medicare Part D Star Ratings adherence classes: diabetes medications, renin-angiotensin system antagonists, and statins.
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Runs on this device. Nothing you enter is sent anywhere. Don't include names or record numbers.
Measurement period
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How it works
- For each drug, the treatment period runs from its first fill in the measurement period (the index date) to the end of the period. Fills before the period are listed but not counted.
- When a refill of the same drug comes before the last supply runs out, its start is shifted to the day after, so early refills add days instead of overlapping. Supply past the end of the period is not counted.
- For a class, days covered by any drug in the class count once, without shifting between different drugs (switching lisinopril to losartan doesn't double count). The class treatment period starts at the first fill of any drug in the class.
- PDC = covered days ÷ days in the treatment period. 80% or higher is adherent. To be in a Star Ratings adherence measure, a person needs at least two fills on different dates in the class. Insulin users are excluded from the diabetes measure and sacubitril/valsartan users from the RAS measure; hospice and ESRD exclusions also apply.
- The refill-by date is the latest day the next fill could start, with continuous supply after it, and still end the period at 80%.
- Drugs are matched by generic or common brand name to a curated list built from the measure descriptions (biguanides, sulfonylureas, thiazolidinediones, DPP-4 inhibitors, GLP-1 and GIP/GLP-1 agonists, meglitinides, SGLT2 inhibitors; ACE inhibitors, ARBs, and aliskiren; statins). It approximates, but is not, the licensed PQA medication list. Hospital stays and skilled nursing days, which the official measure adjusts for, are not handled.
Sources
- CMS: Part C and D Star Ratings technical notes: Part D measure definitions for medication adherence for diabetes medications, hypertension (RAS antagonists), and cholesterol (statins)
- Pharmacy Quality Alliance: adherence measures: PQA stewards the PDC measure specifications and medication lists
Educational estimate. This is not an official CMS calculation and is not for billing, payment, or quality reporting. Plan-reported adherence uses claims data, the full PQA value sets, and inpatient and SNF day adjustments, so results can differ.