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The ACG Case-Mix System is a person-focused method of categorizing patients'
illnesses. Over time, each person develops a constellation of conditions. Based
on the pattern of these morbidities, the ACG System approach assigns each individual
to a single group (an "ACG") which permits the effects of a clustering
of morbidities to be captured in estimates of resource use.
The ACG Case-Mix System assigns all ICD-9-CM codes to one
of 32 diagnosis groups, known as Adjusted Diagnosis Groups (ADGs.) Diseases are placed
in a diagnosis group (ADG) based on five clinical dimensions:
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Duration (acute, recurrent or chronic):
How long will health care resources be required for the
management of this condition?
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Severity (minor/stable versus major/unstable):
How intensely must health care resources be applied to
manage the condition?
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Diagnostic Certainty (symptoms versus
diseases): Will a diagnostic evaluation be needed (symptoms)
or will services for treatment be the primary focus (diseases/diagnoses)?
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Etiology (infectious, injury or other):
What types of health care services will be used?
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Specialty Care (medical, surgical,
obstetric, hematology, etc.): To what degree will specialty
care services be required?
All diseases, even those newly discovered, can be classified
along these dimensions and categorized into one of these
32 groups.
Because most management applications for population-based,
case-mix adjustment systems require that patients be grouped
into single, mutually exclusive categories, the ACG Case-Mix
System uses a branching algorithm to place people into one
of 93
discrete ACG categories. An individual is assigned to
an ACG based on his or her particular combination of ADGs
as well as his or her age and gender. The result is that
individuals within a given ACG have experienced a similar
pattern of morbidity and resource consumption over the course
of a given year.
ACGs use readily available information derived from both
out-patient or "ambulatory" physician visit claims
records and in-patient or hospital claims data.
Typically, ACGs perform up to 10 times better than age and
gender adjustment, which remains the most common risk-adjustment
mechanism in the insurance industry today.
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