Although baseline serum creatinine levels are essential to diagnose acute renal damage, they are frequently unavailable. For a study, researchers sought to estimate creatinine for a study, so they tested four traditional models. They then created and tested a new equation adjusted for age and gender. They looked at patients who had accessible baseline creatinine values at the time of their initial hospitalization and experienced acute renal damage ≥24 hours later. They divided the study population in half (derivation) to design a novel linear equation and a half (validation) to assess bias, precision, and accuracy against existing equations. They conducted an analysis based on age and gender.

About 3,139 hospitalized people were examined (58% male, median age 71). In patients aged <60 or ≥75, conventional equations fared badly in terms of bias and accuracy (68% of the study population). The revised linear equation was more accurate and had less bias. Precision differences were not clinically significant. The median (95% CI) difference in creatinine values estimated using the new equation minus measured baselines was  0.9 (−3.0, 5.9) and −0.5 (−7.0, 3.7) μmol/L in female patients 18–60 and 75–100, and −1.5 (−4.2, 2.2) and −7.8 (−12.7, −3.6) μmol/L in male patients 18–60 and 75–100, respectively. Compared to the MDRD II equation, the new equation improved the categorization of KDIGO AKI stages by 5.0%. Adjusted equations were less prejudiced and more accurate than unadjusted equations. The new equation performed admirably in terms of bias, precision, accuracy, and reclassification.