The addition of written-prescription data to measures of adherence identified nearly twice as many nonadherent patients and markedly improved prediction of changes in low-density lipoprotein (LDL) cholesterol, according to a study published in the October issue of The American Journal of Managed Care.

Shepherd Roee Singer, MD, MPH, and colleagues at the Clalit Research Institute in Jerusalem conducted a retrospective database analysis of all health plan members prescribed a statin in 2008 and followed through 2010. The researchers examined statin use in a 4 million member health plan with 100 percent EHR coverage.

Nonadherence to prescribed medication is a pervasive phenomenon, more common in chronic than in acute conditions. Poor adherence to medication regimens has been associated with poor medical outcomes over a range of diagnoses, and poor adherence to statins has been found to be associated with higher healthcare costs and cardiovascular hospitalizations.

Adherence measures used in this study were modeled after the concept of medication possession ratio (MPR) with the addition of written prescription data. The researchers created an MPR-type measure integrating written-prescription data with dispensed data (MPR_p) and compared it with a commonly used version of dispensed only MPR (MPR_d). MPR_d was defined as the number of days of supply divided by the number of days between the day the first medication was dispensed and the day before the last medication was dispensed in the study period. MPR_p was defined as the number of days of supply divided by the number of days between the day the first medication was prescribed and the day before the last medication was prescribed in the study period. MPR_p thus reflects adherence over the period for which statins were known to be prescribed.

A total of 67,517 patients received 1,386,270 written prescriptions over the three-year period. MPR_p identified 93 percent more patients as nonadherent than did MPR_d. These newly identified patients exhibited minimal LDL decreases over the course of the study. Adherence by MPR_p was more strongly associated with decreases in LDL than was adherence by MPR_d.

“With the rapid and accelerating adoption of electronic medical records, prescription data are likely to become available to a wide range of providers,” the authors wrote. “We have shown that integrating these data into dispensary-based adherence measures would more accurately identify nonadherent patients and those unlikely to achieve clinically important LDL reductions, and would provide a superior predictor of LDL reduction. This information should prove important to both clinicians treating patients and to healthcare managers attempting to assess the extent of medication nonadherence and the resources necessary to address it.”