Table 2.

Comorbidity Interactions Using Diabetes as an Example of a Disease That Can Affect the Diagnosis, Treatment, or Prognosis of a Second Disease

Impact on Clinical Activity	Examples
Diagnosis
Made easier by coexisting disease	Most diabetic patients undergo regular fundus examinations, making the diagnosis of unrelated retinal disease, such as age-related macular retinopathy, more likely
Made more difficulty by a coexisting disease	Diabetic patients may have altered pain sensation, thereby interfering with and making more difficult the diagnosis of coronary heart disease
Treatment
Indicated for existing and coexisting disease	Physical exercise as recommended for a patient with chronic obstructive pulmonary disease can have a beneficial effect on diabetes
Antagonistic effect on coexisting disease	Corticosteroids prescribed for chronic obstructive pulmonary disease in the same patient will have an antagonistic effect on the diabetes treatment
Prognosis
Positively modified by a coexisting disease	Mortality associated with diabetes is increased in the presence of peripheral vascular disease
Not affected by a coexisting disease	Diabetes is unaffected by the presence of hypothyroidism