title: A gap analysis approach to assess patient persistence with glaucoma medication.
abstract: OBJECTIVE
  To develop an alternative method for analysis of patient persistence with prescribed medications using the prostaglandin class of intraocular pressure (IOP)-lowering drugs as a model.
  
  
  METHODS
  A retrospective study of prescription refill patterns.
  
  
  METHODS
  Patients with a pharmacy claim for a 2.5 ml bottle of latanoprost, travoprost, or bimatoprost between September 1, 2002 and December 31, 2002 were identified from a retail pharmacy database and were followed up for 12 months. Three separate analyses defined gaps in therapy as spans in excess of 45, 60, or 120 days without a refill for the same medication. Patients were categorized by the number of gaps in therapy and the cumulative length of gaps. A Kaplan-Meier analysis was conducted using a 120-day allowable refill period.
  
  
  RESULTS
  For refill periods of 45, 60, and 120 days, 10.6%, 28.6%, and 77.5% of patients, respectively, had no gaps in therapy, and 32.6%, 53.4%, and 86.5%, respectively, had 30 days or fewer off therapy annually. According to the 45-day threshold analysis, 50.7% of patients had three or more gaps vs 18.5% in the 60-day analysis and none in the 120-day analysis. The Kaplan-Meier curve shows 88.6% and 76.1% of patients were persistent for 120 days and one year, respectively.
  
  
  CONCLUSIONS
  Compared with Kaplan-Meier survival curves, the gap analysis approach may better parallel clinical experience with patient persistence, in which patients stop and restart medications for a variety of reasons over time. This method also may help to identify avenues for investigation of lack of persistency among many patients.
authors: Duke Eye Center, Duke University, Durham, North Carolina, USA. lee00106@mc.duke.edu
authors: Paul P
authors: PP
authors: Lee
authors: John G
authors: JG
authors: Walt
authors: Tina H
authors: TH
authors: Chiang
authors: Angela
authors: A
authors: Guckian
authors: John
authors: J
authors: Keener
mesh_terms: D000577:Amides / Q000008:administration & dosage; D000959:Antihypertensive Agents / Q000008:administration & dosage*; D000069580:Bimatoprost; D003008:Cloprostenol / Q000008:administration & dosage / Q000031:analogs & derivatives; D011307:Drug Prescriptions / Q000706:statistics & numerical data*; D004363:Drug Utilization / Q000706:statistics & numerical data*; D005901:Glaucoma / Q000188:drug therapy*; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D000077338:Latanoprost; D008055:Lipids / Q000008:administration & dosage; D010349:Patient Compliance / Q000706:statistics & numerical data*; D010594:Pharmacies / Q000706:statistics & numerical data*; D011243:Preferred Provider Organizations / Q000706:statistics & numerical data; D011461:Prostaglandins F, Synthetic / Q000008:administration & dosage; D012189:Retrospective Studies; D000069557:Travoprost
chemical_list: D000577:Amides; D000959:Antihypertensive Agents; D008055:Lipids; D011461:Prostaglandins F, Synthetic; D003008:Cloprostenol; D000077338:Latanoprost; D000069580:Bimatoprost; D000069557:Travoprost