CMS Pub. 100-16, ch. 7, § 70.2.7

Disease Interactions - Certain combinations of coexisting diagnoses for an individual

can increase medical costs more than the additive nature of the CMS-HCC model

reflects. The CMS-HCC model recognizes these higher costs by incorporating disease

interactions in the model.

Disabled Interactions - Interactions between certain diseases and disabled status for an

enrollee can increase medical costs. The CMS-HCC model recognizes these higher

costs by incorporating disease and disabled interactions in the model.

In calculating the interaction part of the risk score for an individual, the disease or

disabled interaction factor is added to the remaining factors.

The following example uses the CMS-HCC risk adjustment model used in payment

for years 2009 through 2011:

An individual who is disabled, lives in the community, and has been diagnosed with

rheumatoid arthritis (ICD-9 code 7140, HCC38) and cystic fibrosis (ICD-9 code 2770,

HCC107).

Factor 1: Rheumatoid Arthritis and Inflammatory Connective Tissue, HCC38 = 0.346

Factor 2: Cystic Fibrosis, HCC107 = 0.399

Factor 3: Disabled * Cystic Fibrosis, D_HCC107 = 1.097

Risk Score = (demographics) + 0.346 + 0.399 + 1.097