A-322 Implementation of Three Age- and Sex-Dependent Equations to Estimate Glomerular Filtration Rates (eGFR) at a Pediatric Institution
Authors: Ferguson A , Wiebold A , Weidemann D , Warady B , Garg U 
Published: September 2023

Abstract

Background
The National Kidney Foundation estimates that 37 million people in the United States are affected by kidney disease, although 90% of them are unaware of it. While kidney disease is less common in children and adolescents, early diagnosis and treatment is important due to the significant long-term impact it can have on growth, cognitive development, and cardiovascular disease. Unlike adults, the estimated glomerular filtration rate (eGFR) for pediatric patients is not routinely reported by clinical laboratories. The process of estimating GFR is cumbersome and time-consuming for clinicians, requiring data extraction to use estimating equations with variable accuracy. The Chronic Kidney Disease in Children (CKiD) Study has developed and published new, more precise, estimating equations for use in children and young adults that utilize a sex- and age-dependent constant (k) in conjunction with height and serum creatinine and/or serum cystatin-C. In collaboration with Nephrology and Laboratory Information Technology, we implemented three eGFR equations into our laboratory information system (LIS) and currently report the results in the patient's electronic medical record (EMR).

Methods
The three equations that were implemented were named eGFR-creatinine (eGFR = k x (height/sCr) with height in m and serum creatinine in mg/dL), eGFR-cystatin (eGFR = k×(1/cysC) with serum cystatin-C in mg/L), and eGFR-average, which reports the average of the creatinine and cystatin-C estimating equations when both are ordered. The k constant is dependent on the patient's age and sex. An eGFR value of &gt;90 mL/min|1.73m2 is considered normal. When an eGFR is ordered, the system identifies the most recent creatinine or cystatin-C result. If one has not been resulted in the last 2 hours, the system reflexes an order for a basic metabolic panel or a cystatin-C. For the eGFR-creatinine equation, the system looks back up to 3 months for a height and uses the most current value. Concordance and discordance were determined in patients who had all three equations ordered and compared as to whether all three values gave a result above or below 90 mL/min|1.73 m2.

Results
The eGFR-creatinine equation went live in June 2022. As of January 2023, 287 eGFR-creatinine values have been resulted. The cystatin-C assay, eGFR-cystatin equation, and e-GFR average equations went live in November 2022. As of January 2023, 114 eGFR-averages and 167 eGFR-cystatins have been resulted. When both equations were ordered and the eGFR-average was calculated, all three values were concordant 69 times (61%) and discordant 45 times (39%). In 26 instances, the eGFR-creatine value was discrepant compared with the other two equations and in 19 instances, the eGFR-cystatin value was discrepant. The differences between the eGFR equations ranged from 1.1–41.9%, however 65% of the values varied by less than 10% and 88% varied by less than 20%.

Conclusion
Implementation of pediatric eGFR equations into the LIS and reporting of eGFR in the EMR will allow more accurate assessment of pediatric patients’ kidney function and improved clinician and patient awareness of impaired kidney function. Availability of this information will allow an earlier diagnosis and treatment of chronic kidney disease.