This document discusses several methods for measuring medication adherence and persistence using retrospective databases, including MPR (medication possession ratio), CMG (continuous measure of medication gaps), ELPT (estimated level of persistence), and PDC (proportion of days covered). These measures are calculated based on days' supply of medication, treatment duration, gaps between refills, and proportion of time a patient has access to medication. The document provides examples of how each measure is calculated and emphasizes their use in evaluating long-term medication use patterns over time.

1. SHAIST, R.Choi

2. 1. Andrew M et al. A Checklist for Medication Compliance and Persistence Studies Using
Retrospective Databases. Value Health. 2007 Jan-Feb;10(1):3-12
2. Steiner JF, Koepsell TD, Fihn SD, Inui TS. A general method of compliance assessment
using centralized pharmacy records. Description and validation. Med Care 1998;26:814–
23.
3. Farmer KC. Methods for measuring and monitoring medication regimen adherence in
clinical trials and clinical practice. Clin Ther 1999;21:1074–90.
4. Gundula Krack et al. Drugs Real World Outcomes. 2016 Sep; 3(3): 265–278. Claims Data A
nalysis of Tumor Necrosis Factor Inhibitor Treatment Dosing Among Patients with Rheum
atoid Arthritis: A Systematic Review of Methods
5. ELPT: Benner JS, Glynn RJ, Mogun H, et al. Long-term persistence in use of statin therapy
in elderly patients. JAMA 2002;288:455–6.
6. PDC: Li P et al. Adherence, discontinuation, and switching of biologic therapies in medicai
d enrollees with rheumatoid arthritis. Value Health. 2010 Sep-Oct;13(6):805-12

3.  MPR(Medication possession ratio )  “Chronic”
 Days of supply, DOS (e.g., 60 tablets BID  30 days supply)
 MPR(%) =Sum of days of supply(총처방일수)/ T (관찰기간)
 CMG (continuous measure of medication gaps)  “Acute, multiple Rx”
 Sum of the days in the gaps between refills in the observation period is divi
ded by time between the first and last fills
 The percentage of time the patient does not have the medication available f
or use.
 CMG(%)=Number of days of medication supplied within the refill interval/
number of days in refill interval
90 90 90 30 90 120 90 90 30 90
MPR = 540/810 = 66.6%
Andrew M et al. Value Health. 2007 Jan-Feb;10(1):3-12

4.  Persistence adds the dimension of time to the analysis
 The time over which a patient continues to fill a prescription, or the time from the ini
tial filling of the prescription until the patient discontinues refilling a prescription
 ELPT, Estimated level of persistence
 the percentage of individuals remaining on therapy (persistent) at a given time
 ELPT(%)=Proportion of patients refilling each subsequent prescription with (X*days
supplied) from fill n
 Persistence Curve (similar to Kaplan–Meier curve), Early drop out detection
Andrew M et al. Value Health. 2007 Jan-Feb;10(1):3-12

5.  PDC, Proportion of days covered(0-1 or %)
 A measure of patient compliance that has been used with increasing frequency
 the PDC has the advantage of simultaneously reflecting both C&P
Proportion of days covered according to Li et al. for subcutaneous drugs. DOS days of supply
Option
Andrew M et al. Value Health. 2007 Jan-Feb;10(1):3-12
Gundula Krack et al. Drugs Real World Outcomes. 2016 Sep; 3(3): 265–278
“Dosing considered”

6.  Example : PDC
Mean, Median, and Interquartile Range of the Proportion of Days Covered by Statin for Each Interval
Gundula Krack et al. Drugs Real World Outcomes. 2016 Sep; 3(3): 265–278
Li P et al. Value Health. 2010 Sep-Oct;13(6):805-12

7.  Persistent days : number of days to discontinuation and number of
prescription refills over a period of time
 The number of days to discontinuation
▪ a simple count of days from the index prescription to the date of the final
dispensing
▪ Option : inclusion of the days for which the final fill (e.g., final 30 days)
 The number of refills
▪ usually within 12 months of the index fill, could include patients who refill long
after the allowed 30- or 60-day gap for being considered non-persistent.
 “As needed medicine” e.g., treatments for seasonal allergy
90 30 90 30 90 210 90 30 90
Persistent days = 390 days
Gap days = 90 days
Persistent days = days supply + off days
If max off days > gap days(90days), then the patient is not persistent
Index date
off days off days off days
Option
Andrew M et al. Value Health. 2007 Jan-Feb;10(1):3-12