Kidney function biomarker penKid®

Acute kidney injury affects 1 in 3 patients in intensive care units (ICU). Timely information on kidney function is therefore of high importance to early initiate nephron-protective strategies. Existing creatinine-based estimations of the glomerular filtration rate (eGFR) routinely used in critical care settings are unspecific, error-prone and have a substantial time delay. An emerging body of evidence demonstrates that the biomarker proenkephalin, detectable with the IB10 sphingotest® penKid® overcomes these limitations by indirectly measuring the levels of the kidney stimulating hormone enkephalin which reflects the true glomerular filtration rate (true GFR). Measuring penKid® levels reveals kidney function in real-time and offers a blood-based alternative for the in vivo measurement of true GFR.

Independent of comorbidities and the frequently occurring inflammation in critically ill patients, rising penKid® blood levels (1) predict acute kidney injury up to 48 hours earlier than today’s standard of care and decreasing levels (2) show the normalization of kidney function.


  • is a blood-based parameter that correlates with true GFR
  • admission levels provide direct information about kidney function
  • relative changes in blood concentration promptly show the improvement or deterioration of kidney function
  • can be used without restriction in all patients on ICU
  • predicts acute kidney injury up to 48 hours before the standard of care
  • was validated in more than 40,000 patients

Kidney function diagnostics with penKid®

Kidney function is stimulated by the hormone enkephalin which remained hard to detect. penKid® overcomes this limitation by measuring a stable fragment that results out of enkephalin processing. The median penKid® concentration of 4,643 healthy subjects was 45 pmol/L; the 99th percentile was 80 pmol/L.4



The assay for the kidney function biomarker Proenkephalin

IB10 sphingotest® penKid® is a rapid point-of-care (POC) immunoassay for the quantitative in vitro determination of Proenkephalin (penKid®) in EDTA human whole blood and plasma.

Nexus IB10


1. Beunders et al (2020), Proenkephalin compared to conventional methods to assess kidney function in critically ill sepsis patients, Read more
2. Beunders et al (2020), The effects of physical exercise on the assessment of kidney function, Read more
3. Depret et al (2020), PenKid measurement at admission is associated with outcome in severely ill burn patients, Read more
4. Hartman et al (2020), Proenkephalin as a new biomarker for pediatric acute kidney injury - reference values and performance in children under one year of age , Read more
5. Kim et al (2020), Proenkephalin predicts organ failure, renal replacement therapy, and mortality in patients with sepsis, Read more
6. Liu et al (2020), The value of plasma pro-enkephalin and adrenomedullin for the prediction of sepsis-associated acute kidney injury in critically ill patients, Read more
7. Emmens et al (2019), Proenkephalin, an opioid system surrogate, as a novel comprehensive renal marker in heart failure, Read more
8. Kanagala et al (2019), Proenkephalin and prognosis in heart failure with preserved ejection fraction: a GREAT network study, Read more
9. Legrand et al (2019), One-year prognosis of kidney injury at discharge from the ICU: A multicenter observational study, Read more
10. Moledina et al (2019), Penkid: a novel biomarker of reduced GFR in sepsis, Read more
11. Molvin et al (2019), Bioactive adrenomedullin, proenkephalin A and clinical outcomes in an acute heart failure setting, Read more
12. Rosenqvist et al (2019), Proenkephalin a 119–159 (penKid) – a novel biomarker for acute kidney injury in sepsis: an observational study, Read more
13. Breidthardt et al (2018), Proenkephalin for the early detection of acute kidney injury in hospitalized patients with chronic kidney disease, Read more
14. Caironi et al (2018), Circulating proenkephalin, acute kidney injury, and its improvement in patients with severe sepsis or shock, Read more
15. Donata et al (2018), Analytical performance of an immunoassay to measure proenkephalin, Read more
16. Gayat et al (2018) Back-to-back comparison of penKID with NephroCheck® to predict acute kidney injury at admission in intensive care unit: a brief report, Read more
17. Hollinger et al (2018), Proenkephalin A 119-159 (Penkid) is an early biomarker of septic acute kidney injury: the kidney in sepsis and septic shock (Kid-SSS) study, Read more
18. Kieneker et al (2018), Proenkephalin and risk of developing chronic kidney disease: the prevention of renal and vascular end-stage disease study, Read more
19. Siong Chan et al (2018), Proenkephalin in heart failure, Read more
20. Wu et al (2018), The biological variation of plasma proenkephalin: data from a stable heart failure cohort, Read more
21. Beunders et al (2017), Proenkephalin (PENK) as a Novel Biomarker for Kidney Function, Read more
22. Kieneker et al (2017), Plasma proenkephalin and poor long-term outcome in renal transplant recipients, Read more
23. Kim et al (2017), Proenkephalin, neutrophil gelatinase-associated lipocalin, and estimated glomerular filtration rates in patients with sepsis, Read more
24. Matsue et al (2017), Clinical correlates and prognostic value of proenkephalin in acute and chronic heart failure, Read more
25. Mossanen et al (2017), Elevated soluble urokinase plasminogen activator receptor and proenkephalin serum levels predict the development of acute kidney injury after cardiac surgery, Read more
26. Ng et al (2017), Proenkephalin, renal dysfunction, and prognosis in patients with acute heart failure: A GREAT network study, Read more
27. Schulz et al (2017), High Level of fasting plasma proenkephalin-A predicts deterioration of kidney function and incidence of CKD, Read more
28. van Kimmenade et al (2017), Worsening renal function in heart failure: it takes 2 to tangle, Read more
29. Arbit et al (2016), Prognostic usefulness of proenkephalin in stable ambulatory patients with heart failure, Read more
30. Marino et al (2015), Diagnostic and short-term prognostic utility of plasma proenkephalin (pro-ENK) for acute kidney injury in patients admitted with sepsis in the emergency department, Read more
31. Shah et al (2015), Proenkephalin predicts acute kidney injury in cardiac surgery patients, Read more
32. Ng et al (2014), Proenkephalin and prognosis after acute myocardial infarction, Read more