Comorbidity (also referred to as polypathology) refers to the number and type of health problems that a patient has. As one would expect, a patient’s health status declines as the number and severity of health problems increase.  There are many algorithms for measuring and monitoring comorbidity which address a variety of needs–the most well-known is the Charlson Comorbidity Score. There is often one or more that is suitable for a particular individual or population.  In this article, 21 comorbidity calculators from The Medical Algorithms Company are presented in groupings to score comorbidities for general usage, and those that are tied to age, disease, cancer, risk, and drugs.

General Comorbidity Scores

Many comorbidity scores were developed for use in a general population. This allows a single tool to be used for all patients, making it easier to integrate the scores into the medical record and to compare outcomes.

Charlson Comorbidity Index (CCI)

Probably the most famous of the general comorbidity scores is the Charlson Comorbidity Score. One limitation is that the weighting on some conditions such as AIDS has changed since the score was initially released. Several authors have modified the score to use more recent data to improve performance.


Comorbidity scores have also been developed to meet specific needs of a specific group. One such group is the elderly, who tend to have more comorbid medical conditions.

Unfortunately some children can have significant health problems. The problems faced by this group differ from those seen in the elderly.


Some diseases may be associated with specific complications that impact the patient more than others. This has resulted in comorbidity scores specific to patients with that disorder.


A subset of disease-related comorbidity scores involves cancer patients. For these patients both the cancer and the comorbid conditions can negatively impact patient outcomes.


Some comorbidity scores can be used to identify a patient who is at increased risk for a complication during hospitalization or a procedure.


Since many significant chronic conditions are treated with medications, the number and type of medications prescribed can give insights into a patient’s condition. The downside is that some conditions are not treated with drugs and so would be missed. The advantage is that prescription data may be readily available in the electronic health record (EHR).

Significance of Comorbidity

Once an appropriate comorbidity score has been selected, it can be used to identify a patient who may:

  1. Make greater use of healthcare resources
  2. Have a worse overall survival prognosis
  3. Have more complications and readmissions
  4. Have depression and a lower quality of life
  5. Have a higher risk of falls and accidents

Identifying a patient at risk gives an opportunity to mitigate these risks. Surgery may need to be deferred until problems have been brought under control. More aggressive follow-up may be appropriate after hospital discharge in order to reduce readmissions.

Take-Home Message

Medical calculators can help to identify a patient with comorbidity. Tracking comorbidity over time may give insight into a patient’s health status and the ability of the health system to address these problems.

To view a broad range of comorbidity calculators, check out our Medal Pack on comorbidity. This resource can help to obtain valuable insights that can improve outcomes.