Acute Kidney Injury (AKI) following cardiac surgery is a significant cause of death worldwide. Xin et al1 stated that about 15-50% of cardiac surgery patients will develop AKI.
In order to optimise renal function in a focused and effective way, it is important that the clinician knows if the patient has AKI at an early stage. To date, the lack of good biomarkers for AKI has hindered early therapeutic intervention and, if used, delayed the withdrawal of nephrotoxic drugs.
Currently, the diagnosis of AKI is based on markers of renal function: an increase in serum creatinine or decrease in urine output. Xin1 stated that in 27.3% of patients who developed AKI post cardiac surgery, diagnosis with serum creatinine was 12-48 hours post operation. In other words, too late!
This is where Neutrophil Gelatinase associated Lipocalin (NGAL) can make a difference. Many studies have used NGAL as a biomarker for early detection of AKI after both paediatric and adult cardiac surgery, with positive conclusions.
Haase et al2 performed a multicentre trial in 11 sites across the US and Europe. They found that patients with an elevated NGAL and an unchanged creatinine were 16 times more likely to need dialysis versus patients with an unchanged NGAL and creatinine. These patients were also 3 times more likely to die during hospitalisation and spent 3 extra days in ICU and 8 additional days in hospital.
These patients would originally be classified as NOT having AKI when using creatinine alone. Their conclusion was that the concept and definition of AKI needed to be reassessed.
In an additional paper3 from 2011 the group stated that:
The measurement of novel renal damage biomarkers, such as NGAL, enable a 24-48 hour earlier diagnosis
of AKI after cardiac surgical procedures. Based on the presence of a biomarker, potentially effective treatments may be initiated or nephrotoxins withdrawn. In addition, NGAL may also provide valuable information for patient management. Prior to a change of guidelines, multicentre randomized studies, using NGAL as an entry criterion, should prove a benefit for the patients or a favourable cost-benefit ratio.
Although there are fewer studies on the cost-benefit ratio of NGAL, Shaw et al4 concluded that urinary NGAL after cardiac surgery appeared to be costeffective in the early diagnosis of AKI. In fact, the weight of evidence supports the use of NGAL at an early stage to identify AKI just as soon as possible.
This improves patient care and can save money for the NHS. The laboratory can, therefore, now play a vital role in the diagnosis of AKI by rapidly alerting the clinician to the patient’s NGAL concentration. The NGAL Test™ from BioPorto employs a turbidimetric method suitable for open channels on clinical chemistry analysers. Plasma or urine results can be obtained in 10 minutes.
1 Xin et al. Urine neutrophil gelatinase-associated lipocalin and interleukin-18 predict acute kidney injury after cardiac surgery :Ren Fail 2008 ; 30:904-13
2 Haase et al. The outcome of NGAL- positive subclinical Acute Kidney Injury. A multicentre Pooled Analysis of Prospective Studies: J. Am. Coll. Cardiol 2011; 1752-61
3 Haase et al. Acute kidney injury after cardiac surgery: early diagnosis with neutrophil gelatinase associated lipocalin; Med Klin Intensivmed Notfmed 2011; 106:111-16
4 Shaw et al. The economic impact and cost effectiveness of urine neutrophil gelatinase-associated lipocalin following cardiac surgery: ISICEM 2010 Critical Care 2010; 14 (Suppl 1):530.
This article was published previously in Alpha Laboratories’ Leading Edge Newsletter – Autumn 2012.