Urinary KIM-1, but not urinary cystatin C, should be corrected for urinary creatinine
2016 (English)In: Clinical Biochemistry, ISSN 0009-9120, E-ISSN 1873-2933Article in journal (Refereed) In press
OBJECTIVES: The interest for tubular damage markers such as urinary cystatin C (U-CystC) and kidney injury molecule-1 (U-KIM-1) grows, especially for the diagnosis of acute kidney injury. The trend to measure proteins in spot urine samples instead of 24-h urine collections calls for adjustment of urine dilution with urinary creatinine (UCr). However, it is not known whether UCr adjustment provides a more true value of basal U-CystC and U-KIM-1 levels than absolute values.
DESIGN & METHODS: This study examines the rationale for UCr correction for U-CystC and U-KIM-1 by exploring the linear relations between U-CystC and U-KIM-1 and UCr, respectively, and the biological day to day variation of absolute concentrations and UCr adjusted values of the two biomarkers.
RESULTS: Both U-CystC and U-KIM-1 concentrations correlated positively with UCr (R=0.37, P<0.001 and R=0.62, P<0.001, respectively) in 378 participants in a community cohort, which indicated a rationale for adjustment with UCr. However, U-CystC/Cr ratio associated negatively with UCr (R=- 0.31, P<0.001), which could indicate a certain amount of 'over-adjustment'. Morning urine collected for 10 consecutive days from 13 healthy volunteers showed a biological day to day variation of 82% for U-CystC, 75% for U-cystC/Cr ratio, 70% for U-KIM-1 and 46% for U-KIM-1/Cr ratio.
CONCLUSIONS: This study supports the use of U-KIM-1/Cr ratio in clinical population studies. Data supporting the use of U-CysC/U-Cr ratio were less convincing and the possible confounding of UCr has to be acknowledged in clinical settings.
Place, publisher, year, edition, pages
Clinical Laboratory Medicine
IdentifiersURN: urn:nbn:se:uu:diva-303902DOI: 10.1016/j.clinbiochem.2016.07.015PubMedID: 27475248OAI: oai:DiVA.org:uu-303902DiVA: diva2:974524