Comorbidity - Diagnosis of Comorbidity - Methods of Evaluation of Comorbidity

Methods of Evaluation of Comorbidity

There are currently several generally accepted methods of evaluating (measuring) comorbidity:

1. Cumulative Illness Rating Scale (CIRS): Developed in 1968 by B. S. Linn, it became a revolutionary discovery, because it gave the practicing doctors a chance to calculate the number and severity of chronic illnesses in the structure of the comorbid state of their patients. The proper use of CIRS means separate cumulative evaluation of each of the biological systems: “0” The selected system corresponds to the absence of disorders, “1”: Slight (mild) abnormalities or previously suffered disorders, “2”: Illness requiring the prescription of medicinal therapy, “3”: Disease, which caused disability and “4”: Acute organ insufficiency requiring emergency therapy. The CIRS system evaluates comorbidity in cumulative score, which can be from 0 to 56. As per its developers, the maximum score is not compatible with the patient’s life. This way patients S’s comorbidity in 73 years of age can be evaluated as of moderate severity (23 points out of 56), however it is not possible to evaluate the prognosis of the patient, because of the absence of the interpretation of the acquired results their connection with a number of prognostic characteristics..
2. Cumulative Illness Rating Scale for Geriatrics (CIRS-G): This system is similar to CIRS, but for aged patients, offered by M. D. Miller in 1991. This system takes into account the age of the patient and the peculiarities of the old age disorders.
3. The Kaplan-Feinstein Index: This index was created in 1973 based on the study of the effect of the associated diseases on patients suffering from type 2 diabetes during a period of 5 years. In this system of comorbidity evaluation all the present (in a patient) diseases and their complications, depending on the level of their damaging effect on body organs, are classified as mild, moderate and severe. In this case the conclusion about cumulative comorbidity is drawn on the basis of the most decompensated biological system. This index gives cumulative, but less detailed as compared to CIRS, assessment of the condition of each of the biological systems: “0”: Absence of disease, “1”: Mild course of the disease, “2”: Moderate disease, “3”: Severe disease. The Kaplan-Feinstein Index evaluates comorbidity by cumulative score, which can vary from 0 to 36. Apart from that the notable deficiency of this method of evaluating comorbidity is the excessive generalization of diseases (nosologies) and the absence of a large number of illnesses in the scale, which, probably, should be noted in the “miscellaneous” column, which undermines (decreases) this method’s objectivity and productivity of this method. However the indisputable advantage of the Kaplan-Feinstein Index as compared to CIRS is in the capability of independent analysis of malignant neoplasms and their severities. Using this method patient S’s, age 73, comorbidity can be evaluated as of moderate severity (16 out of 36 points), however its prognostic value is unclear, because of the absence of the interpretation of the overall score, resulting from the accumulation of the patient’s diseases.
4. Charlson Index: This index is meant for the long-term prognosis of comorbid patients and was developed by M. E. Charlson in 1987. This index is based on a point scoring system (from 0 to 40) for the presence of specific associated diseases and is used for prognosis of lethality. For its calculation the points are accumulated, according to associated diseases, as well as the addition of a single point for each 10 years of age for patients of ages above forty years (in 50 years 1 point, 60 years 2 points etc.). The distinguishing feature and undisputed advantage of the Charlson Index is the capability of evaluating the patient’s age and determination of the patient’s mortality rate, which in the absence of comorbidity is 12%, at 1–2 points it is 26%; at 3–4 points it is 52% and with the accumulation of more than 5 points it is 85%. Regretfully this method has some deficiencies: Evaluating comorbidity severity of many diseases is not considered, as well as the absence of many important for prognosis disorders. Apart from that it is doubtful that possible prognosis for a patient suffering from bronchial asthma and chronic leukemia is comparable to the prognosis for the patient ailing from myocardial infarction and cerebral infarction. In this case comorbidity of patient S, 73 years of age according to this method, is equivalent to mild state (9 out of 40 points).
5. Modified Charlson Index: R. A. Deyo added chronic forms of ischemic cardiac disorder and the stages of chronic cardiac insufficiency to this index in 1992.
6. Index of Co-Existent Disease (ICED): This Index was first developed in 1993 by S. Greenfield to evaluate comorbidity in patients with malignant neoplasms, but was later it also became useful for other categories of patients. This method helps in calculating the duration of a patient’s stay at a hospital and the risks of repeated admittance of the same at a hospital after going through surgical procedures. For the evaluation of comorbidity the ICED index suggests to evaluate the patient’s condition separately as per two different components: Physiological functional characteristics. The first component comprises 19 associated disorders, each of which is assessed on a 4 point scale, where “0” indicates the absence of disease and “3” indicates the disease’s severe form. The second component evaluates the effect of associated diseases on the physical condition of the patient. It assesses 11 physical functions using a 3 point scale, where “0” means normal functionality and “2” means the impossibility of functionality.
7. Geriatric Index of Comorbidity (GIC): Developed in 2002
8. Functional Comorbidity Index (FCI): Developed in 2005.
9. Total Illness Burden Index (TIBI): Developed in 2007.

Analyzing the comorbid state of patient S, 73 years of age, using the most used international comorbidity assessment scales, a doctor would come across totally different evaluation. The uncertainty of these results would somewhat complicate the doctors judgment about the factual level of severity of the patient’s condition and would complicate the process of prescribing rational medicinal therapy for the identified disorders. Such problems are faced by doctors on everyday basis, despite all their knowledge about medical science. The main hurdle in the way of inducting comorbidity evaluation systems in broad based diagnostic-therapeutic process is their inconsistency and narrow focus. Despite the variety of methods of evaluation of comorbidity, the absence of a singular generally accepted method, devoid of the deficiencies of the available methods of its evaluation, causes disturbance. The absence of a unified instrument, developed on the basis of colossal international experience, as well as the methodology of its use does not allow comorbidity to become doctor “friendly”. At the same time due to the inconsistency in approach to the analysis of comorbid state and absence of components of comorbidity in medical universitycourses, the practitioner is unclear about its prognostic effect, which makes the generally available systems of associated pathology evaluation unreasoned and therefore un-needed as well.