"iDoctor – Medical Blog"

OBJECTIVE. The objectives of our study were to develop a model to
predict the probability of reduced renal function after outpatient
contrast-enhanced CT (CECT)—based on patient age, sex, and race and on
serum creatinine level before CT or directly based on estimated glomerular
filtration rate (GFR) before CT—and to determine the relationship
between patients with changes in creatinine level that characterize
contrast-induced nephropathy and patients with reduced GFR after CECT.

MATERIALS AND METHODS. Of 5,187 outpatients who underwent CECT, 963
(18.6%) had serum creatinine levels obtained within 6 months before and 4 days
after CECT. The estimated GFR was calculated before and after CT using the
four-variable Modification of Diet in Renal Disease (MDRD) Study equation.
Pre-CT serum creatinine level, age, race, sex, and pre-CT estimated GFR were
tested using multiple-variable logistic regression models to determine the
probability of having an estimated GFR of < 60 and < 45 mL/min/1.73
m² after CECT. Two thirds of the patients were used to create and
one third to test the models. We also determined discordance between patients
who met standard definitions of contrast-induced nephropathy and those with a
reduced estimated GFR after CECT.

RESULTS. Significant (p < 0.002) predictors for a
post-CT estimated GFR of < 60 mL/min/1.73 m² were age, race,
sex, pre-CT serum creatinine level, and pre-CT estimated GFR. Sex, serum
creatinine level, and pre-CT estimated GFR were significant factors
(p < 0.001) for predicting a post-CT estimated GFR of < 45
mL/min/1.73 m². The probability is [exp(y) / (1 +
exp(y))], where y = 6.21 – (0.10 x pre-CT estimated
GFR) for an estimated GFR of < 60 mL/min/1.73 m², and y
= 3.66 – (0.087 x pre-CT estimated GFR) for an estimated GFR of < 45
mL/min/1.73 m². A discrepancy between those who met
contrast-induced nephropathy criteria by creatinine changes and those with a
post-CT estimated GFR of < 60 mL/min/1.73 m² was detected in 208
of the 963 patients (21.6%).

CONCLUSION. The probability of a reduced estimated GFR after CECT
can be predicted by the pre-CT estimated GFR using the four-variable MDRD
equation. Furthermore, standard criteria for contrast-induced nephropathy are
poor predictors of poor renal function after CECT. Criteria need to be
established for what is an acceptable risk to manage patients undergoing
CECT.

This entry was posted on Tuesday, July 21st, 2009 at 3:17 am and is filed under Health news. You can follow any responses to this entry through the RSS 2.0 feed. You can skip to the end and leave a response. Pinging is currently not allowed.