Nursing costs more than any other element of intensive care. Nurses are all
ocated exclusively to the ICU, and their use can therefore be accurately mo
nitored. The amount of nursing work in the ICU is intimately associated wit
h the severity of illness of the patients. Consequently, the density of nur
sing staff in the ICU can be used as a measure of cost, and the Therapeutic
Intervention Scoring System (TISS) is a reliable tool for measuring their
workload. TISS is therefore often used to compare the costs of alternative
courses of care; it covers direct costs of care, but it should not be used
as a proxy for total costs in the ICU. The users of TISS should consider th
e limitations of the scoring system in some aspects of its development, as
well as the general nature of the definitions of the items included. The ca
reful enunciation of the more generally defined items has therefore to be c
onsidered when it is used in a research project that compares small samples
.