Evaluation of practice patterns for the care of open-angle glaucoma compared with claims data : The glaucoma adherence and persistency study

To perform a chart review to measure the validity of large claims databases in estimating patient cooperation with eyedrop therapy and to assess physician adherence with guidelines for a preferred practice pattern (PPP) using a new metric. Claims database analysis, chart review, and telephone survey. From 10,260 persons who were recently prescribed a prostaglandin eyedrop for open-angle glaucoma (OAG), a sample of 300 charts (3650 visits) was selected for detailed abstraction. Database review of pharmacy refill, diagnostic testing, and visit information, with chart review of a sample of patients from the database and interviews with an overlapping sample of patients and physicians. The individual patient medication possession ratio (MPR), an index estimating the proportion of time that patients have prescribed drug available for use, frequency of examination findings present in charts, and associations between MPR and physician adherence to a PPP. Chart data confirm that the claims database accurately identified the specific glaucoma eyedrop prescribed, but often identified long-term OAG patients as being new to treatment. Physicians frequently used billing codes for OAG in patients with normal visual field tests. Physicians varied dramatically in their adherence to the PPP, performing intraocular pressure measurements, disc evaluations and imaging, and visual field tests on 90% of OAG patients, but carrying out gonioscopy, central corneal thickness measurement, and setting of target intraocular pressure (IOP) on half of patients. Large claims databases permit conclusions regarding patient cooperation with glaucoma eyedrop therapy, but they should be used cautiously in imputing severity of disease and prior treatment history. Physician adherence to practice guidelines varied substantially; thus, scoring systems for physician behavior have promise in measuring outcome improvements related to better care.