Biostatistical aspects of outcome evaluation using TISS-28.

Quantification of therapeutic activities using the Therapeutic Intervention Scoring System (TISS) is an alternative approach to evaluate outcome of patients in intensive care. The reason for using cumulative TISS points is to integrate various adverse events (except mortality) according to the amount of therapeutic effort that they require. The reduced version of TISS with 28 items (TISS-28) allows a reliable assessment of therapeutic activities with limited observer variation, provided that an exact description of all items is given. Measurements can be validated by correlations with established severity of -disease classification systems such as APACHE II. Cumulative TISS-28 values correlate well with length of ICU stay (r = 0.98). On average, 27.2 points/day can be expected in an unselected mixed surgical ICU. Those who die can be included in non-parametric analyses of cumulative TISS values by allocation of arbitrary high values. Quantification of therapeutic interventions is a sensitive measure of outcome in patients who require intensive care but have a low risk of mortality. The usefulness of economic analysis further supports its clinical application.