Intra-day variability of cystatin C, creatinine and estimated GFR in intensive care patients

Clin Chim Acta. 2016 Sep 1:460:1-4. doi: 10.1016/j.cca.2016.06.014. Epub 2016 Jun 14.


Background: Markers of renal function are widely used in intensive care and sudden changes are important indicators of acute kidney injury. The problem is to distinguish between disease progression/improvement from the natural variation in the patient. The aim of the present study was thus to study the normal intraday variation in ICU patients.

Methods: We studied the intra-day variation of creatinine, cystatin C and estimated GFR based on these two markers in 28 clinically stable ICU patients.

Results: The median diurnal coefficient of variation sCV) for creatinine was 3.70% (1.92-9.25%) while the median CV for cystatin C was 3.66% (1.36-8.11%). The corresponding CVs for the estimated GFRs were 2.00% (0.89-9.82%) for eGFRcreatinine and 4.60% (1.65-10.24%) for eGFRcystc.

Conclusions: The eGFRcreatinine values in individual patients were clearly higher than the eGFRcystc values. The median CV for creatinine, cystatin C and the eGFR measurements were below 5% which means that 95% of the test results will vary by <10% between sampling times in stable ICU patients. Differences >10% between sampling times are thus likely to be an indication of changes in biomarker levels due to the disease/treatment.

Keywords: Creatinine; Critical illness; Cystatin C; Renal markers.

MeSH terms

  • Acute Kidney Injury / blood*
  • Circadian Rhythm*
  • Creatinine / blood
  • Critical Care / methods*
  • Cystatin C / blood
  • Glomerular Filtration Rate
  • Humans
  • Kidney Function Tests*


  • Cystatin C
  • Creatinine