138s Abstracts

P116 A COMPARISON OF APACHE II (ACUTE

PHYSIOLOGY AND CHRONIC HEALTH EVALUATION SCORE) AND MODS (MULTIPLE ORGAN DYSFUNCTION SCORE) IN PREDICTING

ICU MORTALITY

Lauren Griffith, John Marshall, Deborah Cook for the

Canadian Critical Care Trials Group McMaster University Hamilton, Ontario,

CaMda

APACHE II, comprised of 12 physiologic variables, age points and chronic health points, is a standard illness severity score used in ICU clinical trials. The MOD score is a newer instrument comprised of physiologic variables reflecting dysfunction in six organ

systems. Both instruments have been validated and are highly predictive of length of ICU stay and mortality. The APACHE II is usually scored on day one in the ICU whereas the MODS is collected serially. Using a pre-existing multi-centre ICU clinical trial database (N =2252), we compared the scores as predictors of ICU mortality using univariate and multivariable

step-wise logistic regression. We compared 1) APACHE II day 1 vs. MODS day 1 and 2) APACHE day 1 vs. MODS serially. Comparing the scores on entry to the ICU univariately, both MODS and APACHE II were significantly related to ICU mortality (pCO.001). Using step-wise logistic regression with no restrictions, MODS entered the model first and APACHE

II was no longer significant after accounting for MODS. MODS stiIl entered the model after accounting for APACHE II. The results of comparing APACHE II day 1 vs. MODS serially collected were similar with MODS outperforming APACHE II to a greater degree. We conclude that the MOD score performed at least as well as the APACHE II at predicting ICU mortality in our ICU population.

P117 ESTIMATION OF TREATMENT EFFECT AND ITS RESOLUTION

USING A TWO-PHASE MIXED MODEL

Lynn Wei Merck Research Laboratory

Rahway, New Jersey

This paper examines fitting a curve on data from a three year two-phase clinical study to investigate alendronate’s treatment effect and its resolution. The first phase is an on-drug phase and the second off-drug phase. There were six treatment groups: placebo, 5 mg, 10

mg and 40/2.5 mg (first three months on 40 mg and then 21 months on 2.5 mg) groups, which had two year on drug and one year off-drug. The other two groups were 20 and 40

mg groups, which were one year on-drug, one year on placebo and one year off-drug. primary endpoints were bone mineral density (BMD), which were measured every three months.

It was desirable to estimate rates of change in BMD during both phases and compare

them among the groups using all the data collected during three years. A piece-wise mixed model was fit to data from the clinical trial. A function of a+/3 log(time+l) was selected since it adequately described BMD change over time. k is easy to see that @/(time+ 1) is the rate of change at that specific time and that comparing slope, /3, among the treatment groups