Therapeutic Intervention Scoring System (TISS) - a method for calculating costs in the intensive care unit (ICU) and intermediate care unit (IMCU)

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The Therapeutic Intervention Scoring System (TISS) quantifies type and number of intensive care treatments. This system, therefore, indicates the work load of intensive care and may be used for calculating costs in the ICU. In the present study, TISS scoring was prospectively performed daily on 653 patients in a 14-bed multidisciplinary ICU of a 1400-bed university hospital. In addition, we scored 952 patients after major surgical procedures treated in a 4-bed IMCU affiliated to a 24-h recovery room. Besides TISS, we registered age, diagnosis, and length of stay in the unit in each patient. Data were entered from January 1 1998 to December 31 1998. A retrospective cost analysis was performed. The cost of each TISS point was derived from the division of the costs for clinical support services, consumption and staff for all patients in 1998 and the sum of TISS points of all patients in 1998. To determine the cost of each patient, the TISS point price was multiplied with the sum of daily and total TISS points of the patients.

In the ICU, the total accumulated TISS score was 174 950 points. This gave an average cumulative TISS score of 268 in these patients. The median length of stay was 10 days and the median SAPS II score was 23 points. The mortality reached 5.05%. A cost analysis revealed a value of 74.66 DM (38.17 Euro) per TISS point, which can be used to calculate the average costs for groups of patients. The daily cost of ICU care was 3183 DM (1627.44 Euro) per patient in survivors and 4079 DM (2085.56 Euro] in nonsurvivors. For mechanically ventilated patients the daily costs averaged 3404 DM (1740.44 Euro], for patients with spontaneous breathing 2501 DM (1278.74 Euro). Daily cost also depended on age (<60 years, 3367 DM [1721.52 Euro]; 60-70 years, 2463 DM [1259.31 Euro]; >70 years, 3487 DM [1782.87 Euro]) and length of stay (<24 h, 2733 DM [1397.36 Euro]; 2-4 days, 2613 DM [1336.01 Euro]; ≥ 5 days, 3658 DM [1870.31 Euro]). Liver transplant recipients consumed 3621 DM (1851.39 Euro) per day, patients after lung transplantation 2971 DM (1519.05 Euro) per day. Patients after major surgical procedures staying less than 24 h reached daily cost of 2733 DM (1397.36 Euro).

In the IMCU, the total accumulated TISS-score was 39,765 points. This gave an average cumulative TISS score of 42 in these patients. The median length of stay was 1.4 days, the median SAPS II score 18 points and the mortality rate 0%. A cost analysis revealed a value of 78.99 DM (40.39 Euro) per TISS point. Postoperative patients in the intermediate care unit staying <24 h consumed 2562 DM (1309.93 Euro) daily.

In conclusion, in this study we could demonstrate an activity based costing methodology which measures the patient-related costs of care in both, ICU and IMCU. The TISS is a valuable tool when evaluating costs in the ICU and in the IMCU. Charging patients to diagnosis related groups allows calculation of costs and resource allocation to different specialties. Comparing the ICU and the IMCU there was a daily cost difference of 171 DM (87.43 Euro) per patient due to a lower workload and lower costs of the nursing staff in the IMCU. These findings support the potential cost saving of managing patients in an IMCU.