In individuals with many comorbidities, the Charlson Comorbidity Index calculator forecasts survival. It comprises 17 elements, each of element is connected to a different health condition that is linked to mortality. Short and long-term outcomes such as function, hospitalization duration, and death rates may all be predicted using the Charlson index. In the article below, you’ll learn how to compute the Charlson Comorbidity Index score.

What is Charlson Index?

Charlson and colleagues created the Charlson Comorbidity Index in 1987 as a means to define comorbid illnesses that may increase mortality risk. This instrument was created to be utilized in longitudinal investigations. The original Charlson Index included 19 categories. However, it has now been reduced to 17 or 12 categories. As a result, the CCI is now one of the most extensively utilized comorbidity grading systems in research and clinical settings, we can also find it in medical services. Also very important to mention is that this concept requires longitudinal studies. Here we must also look at defining comorbidities. Comorbidity is described as the presence of several disorders in the same person. Comorbidity, in its broadest definition, refers to the co-occurrence of physical and mental illnesses, such as dementia caused by organic ailments or emotional alterations caused by endocrinopathies.

History of the Charlson Comorbidity Index

Mary Charlson and colleagues created the Charlson Comorbidity Measure in 1987 as a weighted index to predict the probability of mortality within one year after hospitalization for individuals with various comorbid illnesses. The index had nineteen criteria. Based on the projected 1-year mortality hazard ratio using a Cox proportional hazards model, each condition was given weight from 1 to 6. By adding these weights together we have the Charlson comorbidity score.

Enhanced Charlson index

Richard Deyo and Patrick Romano modified the Charlson index to ICD-9-CM diagnostic and procedure codes and CPT-4 codes in 1992 and 1993, respectively, so that it could be computed using administrative data. Using breast and prostate cancer cases from SEER-Medicare administrative data, Carrie Klabunde and colleagues produced a disease-specific NCI Comorbidity Index in 2000. To identify the conditions reported by Charlson et al, Klabunde et al utilized codes from Medicare administrative data. Given that the NCI Comorbidity Index was established from a cohort of cancer patients, solid tumours, leukaemias, and lymphomas are not included as comorbid conditions. For clinical prognosis and comorbidity adjustment, measures like the Charlson Comorbidity Index and Elixhauser scores are often utilized.

Elixhauser scores

Elixhauser established the Elixhauser comorbidity index in 1998, which is similar to the Charlson comorbidity index. It is a method for quantifying patient comorbidity based on ICD-9-CM and ICD-10 diagnostic codes discovered in administrative data. The Index has undergone revisions throughout time as a result of new health services research.

Comorbidity Index

The NCI Comorbidity Index now includes the remaining 16 Charlson index conditions, bringing the total number of conditions to 14. The NCI Comorbidity Index was created by looking at Medicare claims from the year before the date of diagnosis, ignoring the month of diagnosis. Hospitalizations (Medicare Part A) and physician claims each have their own comorbidity index (Medicare Part B). To limit the danger of false positives, conditions determined by physician claims have to arise more than once throughout 30 days. These indexes were eventually into a single NCI Comorbidity Index, making the analysis more efficient.

How to calculate Charlson Comorbidity Index

There are 17 entries in the Charlson Comorbidity Index calculator. Each item has a variable weight (variable weight depends on on the strength of the item’s relationship with 1-year mortality, as given in the study by Charles et al.) and may be from 0 to 6. This is why certain factors have a maximum score of 1 point (e.g., history of myocardial infarction), while others have a maximum score of 6 points (e.g. metastatic tumour).

ComorbidityScore
Myocardial infarction+ 1
Congestive heart failure+ 1
Peripheral vascular disease+ 1
Cerebrovascular disease+ 1
Dementia+ 1
Chronic pulmonary disease+ 1
Rheumatologic disease+ 1
Peptic ulcer disease+ 1
Liver disease+ 1 if mild, + 3 if moderate/severe
Diabetes+ 1 if controlled, + 2 if uncontrolled
Hemiplegia or paraplegia+ 2
Renal disease+ 2
Malignancy+ 2 if localized, + 6 if metastatic tumor
Leukemia+ 2
Lymphoma+ 2
AIDS+ 6
The table displays the number of points each item or risk of death or risk factors receives

Information about the subject:

If a prognostic comorbidity is not present, patients receive a score of 0 for that condition.

Patients who are 50 years old or also older than that should receive the following bonus points:

  • additional 1 point for being 50-59 years old;
  • 2 points for being 60-69 years old;
  • 3 points for being 70-79 years old; and
  • 4 points for being 80 years old or older.

Charlson Comorbidity Index score

The Charlson Comorbidity Index has a maximum score of 37 points (adjusted for age).

The patient’s 10-year study period survival rate may be computed after rating each comorbidity. We calculate it by using a low-risk group with a 10-year survival rate or odds ratio of 98.3 percent. The formula is as follows:

10-y survival=0.983^({e}^{CCI\cdot 0.9})

where:

  • e – Euler’s number, a mathematical constant equal to about. 2.71828; as well as
  • the Charlson Comorbidity Index (CCI) is a number that is adjusted by age.

Charlson Comorbidity Index calculator – a practical example

Let’s look at a real-life example how to compute the Charlson Comorbidity Index. Characteristics of our statistical model patient include:

The patient is 57 years old and has the following comorbidities: diabetes treated with medication, myocardial infarction (heart attack) 5 years ago, and no other health issues.

Our patient’s Charlson Comorbidity Index score is 3: +1 point for age 50-59, +1 point for managed diabetes, and +1 point for a history of myocardial infarction.

Finally, we may compute this patient’s 10-year survival as follows:

  • 10-y survival=0.983^({e}^{CCI\cdot 0.9})= 0.983^(2.718283 x 0.9)= 0.983^(2.718282.7)= 0.98314.88= 0.7748 = 77.48%