The relationship between alternative medication possession ratio thresholds and outcomes: evidence from the use of...

To examine how changes in the medication possession ratio (MPR) affect the probability of multiple sclerosis (MS) relapses and total and MS-related charges among patients treated with glatiramer acetate (GA).

Data were obtained from i3 InVision™ Data Mart for January 1, 2006 through March 31, 2010. Patients were included if they were diagnosed with MS, initiated therapy with GA, and had continuous insurance coverage from 6 months prior through 24 months after initial use of GA (n=839). Multivariate regressions which controlled for patient characteristics examined the association between achievement of alternative MPR goals and patient relapses and charges.

Patients who achieved an MPR of at least 0.7 had significantly lower odds of relapse than those with MPR thresholds below 0.7, with achievement of a threshold of 0.7, 0.8, or 0.9, associated with an odds ratio of relapse of 0.545 (95% CI=0.351-0.824), 0.568 (95% CI=0.371-0.870), and 0.421 (95% CI=0.260-0.679), respectively. Attaining higher MPR thresholds resulted in larger reductions in direct medical charges, excluding GA and other MS-related drugs. MPR of 0.25 was associated with $1699 lower 2-year total direct medical charges (p=0.009) while a threshold of 0.95 was associated with $2136 lower total charges (p<0.001), compared to patients not reaching these respective thresholds. MPR of 0.90 was associated with $986 lower MS-related charges than for those with MPR<0.90 (p=0.050). Results also revealed an association between patient adherence to GA and statistically significant reductions in charges for specific components of care.

Results are generalizable only to patients with medical and prescription benefit coverage without regard for functional status.

As adherence improved the odds of relapse decreased and charge offsets generally increased. Results suggest that, despite higher costs associated with increased usage of GA, patient outcomes are improved and there are cost-offsets associated with adherent use of GA.