The Risk Score Profile: a novel approach to characterising the risk of populations enrolled in clinical studies.

AIMS Interpreting the results and practice implications of clinical studies requires accurate characterisation of the baseline risk of the population. We evaluated the Thrombolysis in Myocardial Infarction (TIMI) risk score for STEMI as a tool to describe and compare the risk profile of populations enrolled in three clinical trials (InTIME-II, ASSENT-2 and MAGIC) and the National Registry of Myocardial Infarction. METHODS AND RESULTS The risk score was calculated for each patient (N=121,085) and the frequency distribution plotted for each population. The Risk Score Profiles were compared using the Kolmogorov-Smirnov test. The Risk Score Profile demonstrated a striking concordance between the baseline risk of patients in InTIME-II and ASSENT-2 (median scores in each= 3[1,4], P=0.11). In contrast, the distributions in MAGIC (designed to enroll high risk) and NRMI (registry) were shifted significantly toward higher risk (median scores=4[3,5] for MAGIC and 4[2,6] in NRMI, P < 0.0001 for each vs. InTIME-II). A graded relationship between the risk score and mortality was evident in each study (P<0.0001). CONCLUSIONS The frequency distribution of the TIMI Risk Score, or similar tools for risk assessment, may be used to quantify and readily compare the risk profile of populations enrolled in clinical studies.