Researchers identify best predictor of measured glomerular filtration rate in adults
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Key takeaways:
- Researchers recommend using cystatin C in older adults to predict measured glomerular filtration rate.
- More research needs to be done.
Researchers identified the most accurate estimate of measured glomerular filtration rate is derived from the lower eGFR between creatinine-based eGFR and cystatin C-based eGFR in older adults, according to data published in Kidney Medicine.
“Better assessment of kidney function in older persons is needed to improve clinical care and drug dosing. Kidney function is calculated using serum creatinine, cystatin C or both (creatinine-based estimated glomerular filtration rate [eGFR] vs. cystatin C–based eGFR [eGFRcys] vs. combined),” O. Alison Potok, MD, from the University of California, San Diego, and colleagues wrote. They added, “We investigated which eGFR was more accurate and less biased compared with measured glomerular filtration rate (mGFR).”
In a diagnostic test study from the Berlin Initiative Study, researchers examined 657 patients who were aged 70 years or older and had iohexol plasma clearance and serum creatinine and cystatin C measurements. Of these patients, 567 were community-dwelling and 90 patients had serum creatinine of at least 1.5 mg/dL.
Patients were categorized into three groups based on the difference of creatinine-based estimated glomerular filtration rate (eGFRcr)subtracted from eGFRcys. Those with an eGFRcys of less than 5 mL/min/1.73 m2 were defined as having lower eGFRcys. Patients with eGFR of 5 mL/min/1.73 m2 served as the reference and those with anything greater than that measurement were considered as having lower eGFRcr.
To determine the bias and accuracy of the assessments, researchers compared eGFRcr, eGFRcys and combined creatinine- and cystatin C–based estimated glomerular filtration rate (eGFRcr-cys) values to mGFR).
Overall, 337 patients fell in the lower eGFRcys group and compared with the other groups, the median bias for eGFRcys was the lowest. However, compared with those in the eGFRcys and eGFRcr-cys groups, 121 patients in the lower eGFRcr group had the lowest eGFRcr.
Researchers identified an accuracy percentage of 93% for eGFRcr in the lower eGFRcr group and 92% for eGFRcys and 94% for eGFRcr-cys in the lower eGFRcys group.
“Our findings are relevant to older adults and will have to be replicated and validated in future studies and confirmed in other populations,” Potok and colleagues wrote. “Guidelines already suggest the use of cystatin C, and our findings support its use in older populations because it may be the more accurate estimate of mGFR in those who have a lower eGFR by this estimate.”
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