Assessment of Modification of Diet in Renal Disease Equation to Predict Reference Serum Creatinine Value in Severe Trauma Patients: Lessons From an Observational Study of 775 Cases.
OBJECTIVE
We assessed the Modification of Diet in Renal Disease (MDRD) performance to predict serum creatinine (SCr) in severe trauma population and determined the best theoretical glomerular filtration rate (GFR) to use in this estimation.


BACKGROUND
Baseline SCr may be misestimated in severe trauma patients because of their specific demographic characteristics including renal hyperfiltration. However, the back-calculated MDRD equation is supposed to estimate SCr using a predetermined GFR of 75 mL/min/1.73 m.


METHODS
All severe trauma patients with a normal SCr were retrospectively included between January 2005 and January 2011. For each patient, the lowest SCr (oSCr) observed during the first week was used to estimate the GFR. The median GFR in period 1 (2005-2006) was determined. The back-calculated MDRD performance was assessed in period 2 (2007-2011) to predict oSCr by agreement, precision, and accuracy using a GFR of 75 mL/min/1.73 m (eSCr75-MDRD) or the median GFR observed in period 1 (eSCrTRAUMA-MDRD).


RESULTS
A total of 775 patients were studied: mean age, 37.7 ± 17 years; mean Injury Severity Score, 19 ± 11; 75% of male. In period 1 (n = 243), median GFR was 121 mL/min/1.73 m. In period 2 (n = 532), eSCrTRAUMA-MDRD demonstrated better agreement in predicting oSCr than eSCr75-MDRD (mean bias 2 vs 35 μmol/L; P < 0.001). Both precision (14 vs 39 μmol/L, respectively) and accuracy were significantly improved with eSCrTRAUMA-MDRD. Proportion of estimated SCr values that deviated less than 15%, 30%, or 50% was also higher with eSCrTRAUMA-MDRD (P < 0.001).


CONCLUSIONS
The eSCr75-MDRD equation systematically overestimates oSCr of severe trauma patients. The eSCrTRAUMA-MDRD equation determined was statistically superior allowing more accurate qualification of acute kidney injury.