The US National Institute of Standards and Technology (NIST) has developed the first human urine standard with precise measurements of albumin, a biomarker used in combination with creatinine to assess kidney health.
Standards exist to support measurements of creatinine. However, until now, there were no standards for albumin in human urine; instead, that standard was based in serum.
"The ideal standard is always in the same material as the clinical sample," said bioanalytical chemist Ashley Beasley-Green, who leads NIST's urine albumin standardization program. "If you send a urine sample to a lab, you expect the quality control material to be the same."
A unit of the new standard reference material, SRM 3666, consists of four vials of frozen pooled human urine with four different levels of endogenous albumin, determined using the NIST candidate reference measurement procedure for albumin in urine and creatinine in urine.
The certified values and associated uncertainties for albumin and creatinine were used to calculate the albumin-to-creatinine ratio for each level. The SRM comes with a data sheet that gives measures of how much albumin and creatinine are in each vial.
"We need precise clinical measurements so clinicians can make accurate decisions," Green said. "This SRM directly impacts the health of individuals and the quality of care they receive. It’s hard to determine the risk of kidney disease with inconsistent test results."
To support the accuracy and comparability of the urine albumin measurements, NIST partnered with the National Institute of Diabetes and Digestive and Kidney Diseases and the International Federation of Clinical Chemistry Working Group for the Standardization of Albumin Assays in Urine.
Laboratories that test urine samples can use the SRM for quality control, NIST suggests. Researchers can run the material through their instruments, and if their results match the numbers on the SRM data sheet, then they can have greater assurance their instruments are working correctly. The SRM could also affect clinical guidelines down the road.
International studies, including interlaboratory comparisons that use the SRM, will be conducted to further confirm that the material meets the needs of the medical community, from clinical labs to assay manufacturers.
The development, production, and certification procedures are described in the NIST special publication, Certification of Standard Reference Material 3666 Albumin and Creatinine in Frozen Human Urine.
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