Kidney Week

Abstract: SA-PO921

Measured GFR Implemented in a US Clinical Practice: Comparing 4-Hour and 10-Hour Plasma Iohexol Clearance

Session Information

• Pathology and Lab Medicine - 2
  October 26, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Pathology and Lab Medicine

• 1800 Pathology and Lab Medicine

Authors

• Bobart, Shane A., Houston Methodist Hospital, Houston, Texas, United States

Shane A. Bobart, MD, FASN

• Nielsen, Jacob, Houston Methodist Hospital, Houston, Texas, United States

Jacob Nielsen, PhD

• Yi, Xin, Houston Methodist Hospital, Houston, Texas, United States

Xin Yi, PhD

• Edwards, Angelina, Houston Methodist Hospital, Houston, Texas, United States

Angelina Edwards, MD, FASN

• Shafi, Tariq, Houston Methodist Hospital, Houston, Texas, United States

Tariq Shafi, MBBS, MHS, FASN

Background

It is well recognized that estimated glomerular filtration rate (eGFR) can be highly inaccurate in assessing measured GFR (mGFR) for individual patients. mGFR using non-radiolabeled plasma iohexol clearance is straightforward and easily implementable in clinical practice, but it is not widely available in the US. In 2019, we implemented mGFR by a 4-hour plasma iohexol clearance as part of clinical care at Houston Methodist Hospital. The mGFR is orderable via an Epic order set. Recent studies (White CA; PMID: 32750458) and European Kidney Function Consortium (EKFC; under review) guidelines emphasize the importance of a long plasma clearance interval (10-hours) if the GFR is expected to be low (<30 mL/min/1.73 m²). We have now updated our mGFR protocols to include both the standard (4-hour) and the long (10-hour) clearances. We present these case studies as an educational tool to enhance the understanding of mGFR and promote dissemination of mGFR protocols.

Methods

We describe 3 patients that had simultaneous measurement of creatinine, cystatin C, and mGFR by 10 hour plasma iohexol clearance. We compared the 4-hour and 10-hour mGFRs with eGFRs. We defined eGFR to be accurate in assessing the mGFR if the eGFR was within ±5 ml/min/1.73 m² of the 10-hour mGFR.

Results

See Table 1.

Conclusion

mGFR is the best available test of kidney function and it is not influenced by age, sex, or race. We have successfully implemented standard (4-hour) and long (10-hour) mGFR in routine practice at a busy clinical center in the US. Our cases provide important educational opportunities for nephrologists interested in learning and implementing mGFR in routine clinical care.