Table 1: Charlson Index of comorbidity [8].
| Clinical condition | Weight |
| 50-60 years old | 1 |
| Myocardal infarction | 1 |
| Congestive heart failure | 1 |
| Peripheral vascular disease | 1 |
| Cerebrovascular disease | 1 |
| Dementia | 1 |
| Chronic obstructive pulmonary disease | 1 |
| Connective tissue disease | 1 |
| Ulcer disease | 1 |
| Mild liver disease | 1 |
| Slight Diabetes without complication | 1 |
| 61-70 years old | 2 |
| Hemiplegia | 2 |
| Moderate to severe renal disease | 2 |
| Diabetes with en-organ damage | 2 |
| Tumors | 2 |
| Leukemia | 2 |
| Lymphoma | 2 |
| 71-80 years old | 3 |
| Moderate to severe liver disease | 3 |
| Up to 90-years-old | 6 |
| Metastatic solid tumor | 6 |
| Acquired immunodeficiency syndrome | 6 |