mmpc - National Indian Health Board

Methods
on five clinical dimensions: 1) Duration of the condition (acute, recurrent, or chronic); 2) Severity of
the condition (e.g., minor and stable versus major and unstable); 3) Diagnostic certainty (symptoms
versus documented disease); 4) Etiology of the condition (infectious, injury, or other); and 5)
Specialty care involvement (e.g., medical, surgical, obstetric, hematology). The Aggregated Diagnosis
Groups are then weighted and added so that a single ACG morbidity (risk) score is obtained by each
individual.
The ACG system provides an external standard sample of privately insured population in a managed
care plan for reference, but the system recommends use of an internal reference group to
standardize for unadjusted differences between Medicaid populations and provider claims and
privately insured managed care data. We used the random sample of non-Hispanic White Medicaid
recipients living in the same counties as the AIAN as the morbidity reference group.
The software is not recommended for use without a 12 month continuous claim history for
recipients, and therefore we did not apply it to recipients with less than 12 months enrollment. We
did not use the feature of the software that uses pharmacy data because we found that IHS AIAN in
the Medicaid data had much lower pharmacy payments than other which is likely due to access to
medications through their Indian healthcare providers, which Other AIAN and Whites do not have
(see Prescription Drug FFS data in the Findings section).
Statistical Adjustments
To adjust for the effects of determinants on mean total payments per recipient, we constructed
Generalized Linear Mixed Models of SAS statistical software (version 9.2) using the log-likelihood
function, assuming the gamma distribution of the dependent variable (Medicaid payments). We
have previously published studies using these methods with Medicaid claims data (Wong et al,
2006), including using the ACG risk adjustment (Korenbrot, Kao & Crouch, 2009).
Medicaid Enrollee Exclusions were: 1) enrollees with no known months of eligibility, 2) enrollees
with longterm or institutionalized care, 3) enrollees with ‘Restricted’ rather than ‘Full’ Medicaid
benefits, and 4) enrollees with no paid claims of $1 or more. Recipients remaining were then
grouped for analytical modeling as in Table 9:
15