Since the “CDC definition” of daily milligrams of morphine equivalence (MME) lacks a clearly defined denominator, the objective of the reported research was to assess denominator-dependency on “high dose” classification across competing definitions.
To identify definitional variants, the study reviewed literature and electronic prescribing tools, yielding four unique definitions. Using Prescription Drug Monitoring Programs data (July to September 2018), the study conducted a population-based cohort study of 3,916,461 patients receiving outpatient opioid analgesics in California (CA) and Florida (FL). The binary outcome was whether patients were deemed “high dose” (>90 MME/d) compared across four definitions. The study calculated I2 for heterogeneity attributable to the definition. Among 9,436,640 prescriptions, 42 percent overlapped, which led denominator definitions to impact daily MME values. Across definitions, average daily MME varied 3-fold (range: 17 to 52 [CA] and 23 to 65 mg [FL]). Across definitions, prevalence of “high dose” individuals ranged 5.9 percent to 14.2 percent (FL) and 3.5 percent to 10.3percent (CA). Definitional variation alone would impact a hypothetical surveillance study trying to establish how much more “high dose” prescribing was present in FL than CA: from 39 percent to 84 percent more. Meta-analyses revealed strong heterogeneity (I2 range: 86 percent to 99 percent). In sensitivity analysis, including unit interval 90.0 to 90.9 increased “high dose” population fraction by 15 percent. Although 90 MME may have cautionary mnemonic benefits, without harmonization of calculation, its utility is limited. Comparison between studies using daily MME requires explicit attention to definitional variation. (publisher abstract modified)