Using the MDRD value as an outcome predictor in emergency medical admissions

Abstract

Both physiological- and laboratory-derived variables, alone or in combination, have been used to predict mortality among acute medical admissions. Using the Modification of Diet in Renal Disease (MDRD) not as an estimate of glomerular filtration rate but as an outcome predictor for hospital mortality, we examined the relationship between the MDRD value and in-hospital death during an emergency medical admission. An analysis was performed on all emergency medical patients admitted between 1 January 2002 and 31 December 2008, using the hospital in-patient enquiry system, linked to the patient administration system and laboratory datasets. Hospital mortality (any in-patient death within 30 days) was obtained from a database of deaths occurring during the same period under physicians participating in the 'on-call' roster. Logistic regression was used to calculate unadjusted and adjusted odds ratios (OR) and 95% confidence intervals (CI) for MDRD value. Univariate analysis identified those with MDRD value of <60 as possessing increased mortality risk. Their 30-day mortality rate was 21.63 versus 4.35% for patients without an abnormal value (P < 0.0001) with an OR of 6.07 (95% CI's 5.49, 6.73: P < 0.001). After adjustment for 12 other outcome predictors including comorbidity, the OR was 4.63 (4.08, 5.25: P < 0.0001). Using the Kidney Disease Outcomes Quality Initiative (KDOQI) class, the respective mortality rates by 30 days increased with a lower MDRD value, from 2.8% in KDOQI Class 1 to 48.6% in KDOQI Class 5. Outcome prediction of in-hospital death, at 5 and 30 days with the MDRD, yielded areas under the receiver operator curves of 0.84 (0.83, 0.84) and 0.77 (0.77, 0.78). Many factors predict survival following an emergency medical admission. The MDRD value offers a novel readily available and reliable estimate of mortality risk.