Correlation of TISS and Nurse Dependency scores with the pilot version of the SOPRA score

Abstract

A number of severity of illness scoring systems have been developed and are widely used in intensive care practice. The Therapeutic Intervention Scoring System (TISS) is used as a tool for assessing severity of illness, therapeutic and nursing manpower requirements as well as cost-benefit analysis.1 TISS uses over 70 variables, however it does not take into account non-interventional demands on time such as communications and support for relatives. The Lincolnshire demand model for Nurse Dependency (ND) adapted from an earlier model2 is used in our ICU, scoring 1, 2 or 3 with increasing dependence. The Intensive Care National Audit and Research Centre (ICNARC) Working Group released a pilot version of their System of Patient Related Activities (SOPRA) at the Riverside/ICS Meeting in December 1998. SOPRA is intended to indicate the degree of care necessary when treating a critically ill patient. In one score it is hoped to assess the intensity of impact each patient made on the work of the ICU that day. The aim of this study was to test for any association between TISS, SOPRA and ND scores. Daily TISS, SOPRA and ND scores were recorded over a period of 2 months on all patients on our ICU. The results were analysed using non-parametric tests, Spearman's correlation and linear regression methods. We recorded 488 scores for each system (Table 24). Median SOPRA score was 25 (range 12–60), that of TISS was 34 (11–73). There was no correlation between SOPRA and ND scores (r2 = 0.18). There was no correlation between TISS and ND (r2 = 0.14). Despite many similarities between SOPRA and TISS their correlation was poor (r2 = 0.49). Our nursing staff found the SOPRA score more specific and less subjective than TISS. It was also felt to be more representative of current Intensive Care practice. We conclude that the SOPRA and TISS are significantly different scoring systems despite having many common factors. However further evaluation is required to identify any advantage SOPRA may offer over TISS.