NGAL ,CYSTATIN C VERSUS CREATININE CLEARENCE AS A BIOMARKER IN AKI

1. NGAL ,CYSTATIN C
VERSUS CREATININE
CLEARENCE AS A
BIOMARKER IN AKI
Moustafa Rizk , MD
Professor of Clinical Pathology
Alexandria Collage Of Medicine
3/7/2020 4:56 AM 1

2. Acute kidney injury (AKI), previously known as
acute renal failure, after cardiac surgery is
one of the most serious complications during
the postoperative period.
Although the incidence of post-operative AKI is
relatively low, it is associated with strikingly
high mortality rates during hospitalization ,
usually exceeding 50%.
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3. Classification Schemes for Acute
Kidney Injury
As part of the Acute Dialysis Quality Initiative
2nd International Consensus Conference, the
RIFLE (Risk of kidney dysfunction, Injury to
the kidney, Failure of Kidney function, Loss of
kidney function, and End stage kidney disease)
classification scheme was derived to provide
standardized criteria for defining AKI .
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4. Recently, the acute kidney injury network
(AKIN) modified the RIFLE risk criteria
slightly to include an absolute increase in
serum creatinine concentrations of 0.3
mg/dl .
The pediatric RIFLE was found to better
classify pediatric AKI and to reflect the course
of AKI in children admitted to the ICU
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5. Pediatric Modified RIFLE--
definition
Ackan-Arikan et al: Kid Int 2007
Pediatric Modified RIFLE Criteria
CrCl Urine output
Risk GFR decrease by 25% <0.5ml/kg/hour for 8 hours
Injury GFR decrease by 50% <0.5ml/kg/hour for 16 hours
Failure
GFR decrease by 75% or
GFR<35ml/min/1.73m 2
<0.3 ml/kg/hour for 24 hours or
anuric for 12 hours
Loss Persistent ARF > 4 weeks
End
stage
End Stage Renal Disease (>3 months)
GFR per Schwartz equation: GFR= Ht (cm) X constant / serum creat (mg/dl)
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6. AKI RIFLE Criteria: ADQI II
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7. Early detection of AKI in ICU is crucial to
perform early intervention and prevent further
complications, thus it may be lifesaving to
determine the risk factors for the impairment
of the renal function.
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8. Etiology and risk factors for
AKI
1- ATN (acute tubular necrosis) in 50% of cases
with no specific determined cause.
2- Nephrotoxin administration (26%),
3- Cardiac disease (20%) including myocardial
infarction,cardiogenic shock, and congestive heart
failure,
4- ATN from hypotension (12%), sepsis (19%),
5- Unresolved prerenal factors (16%)
6- Liver disease (11%).
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Mehta RL, Pascual MT, Soroko S, Savage BR, Himmelfarb J, Ikizler TA, Paganini EP & Chertow GM: Spectrum of acute
renal failure in the intensive care unit: The PICARD experience. Kidney Int 2004, 66:1613-1621

9. • Risk factors
– Thrombocytopenia
– Older age
– Hypoxemia
– Hypotension
– Coagulopathy
• Increased PRISM and
PELOD scores also AKI
risk factors
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10. Pediatric AKI: Recent
Epidemiology
Age (n) GFR Survival
n (%)
ICU Stay
n (%), LOSa
RRTb
n (%)
Commonest ARF Cause
n (%)
0 – 30 d (62) 11.5  9.8 34 (56%) 59 (97%), 46 34 (58%) Ischemic
16 (26%)
1 – 12 mos (37) 18.4  14.3 22 (59%) 32 (86%), 26 10 (32%) Ischemic
13 (35%)
1 – 6 yrs (43) 32.9  20.1 36 (84%) 30 (70%), 21 8 (27%) Ischemic
10 (23%)
5 – 16 yrs (83) 29.3  20.4 61 (73%) 49 (59%), 18 28 (57%) Nephrotoxins
22 (26%)
16 – 21 yrs (29) 35.5  17 23 (79%) 15(52%), 23 8 (53%) Nephrotoxins
6 (21%)
TOTAL (254) 35.2  39.2 176 (70%) 185 (73%), 26 80 (43%) Ischemic
45 (22%)
a. Average Length of ICU stay, days
b. RRT – Renal Replacement Therapy
Stickle SH et al: Am J Kid Dis 45:96-101, 20053/7/2020 4:56 AM 10

11. Pediatric AKI: Recent Epidemiology
Pediatric ARF: Age Distribution
22%
15%
13%
34%
16%
0 to 30 d
1 to 12 mo
1 to 5 yr
6 to 14 yr
15 to 20 yr
Stickle SH et al: Am J Kid Dis 45:96-101, 2005 11

12. Outcomes in Acute Kidney Injury
after cardiac surgery
Although the overall mortality rates after cardiac
surgery are low (2–5%), the crude mortality rate
among patients who develop AKI can be as high
as 60%, and this accounts for almost half of the
overall hospital deaths during the post-operative
period.
More recently, two large US and European
cohorts demonstrated that even milder degrees
of kidney injury, measured as small increments
in creatinine (or a decline in calculated GFR),
were associated with an increased risk for
death during the post-operative period.
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13. The mortality rate in patients with ~30% decline
in GFR was 4–6% , whereas in those patients
with a 50% drop in GFR it was 15%. In
contrast, the mortality rate in patients without
any elevation in serum creatinine was <1%.
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14. AKI Severity and Outcome
Chertow GM et al: J Am Soc Nephrol, 20053/7/2020 4:56 AM 14

15. Serum creatinine
Infants
Cr in the first few weeks of life may reflect maternal
values
Children
Low baseline Cr makes 0.2-0.3 changes in Cr
significant
Varying muscle mass
Adolescents
Similar to adults
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16. Serum creatinine for AKI
Unfortunately, creatinine is an unreliable
indicator during acute changes in kidney
function :
1-Serum creatinine levels can vary widely with
age, gender, lean muscle mass, muscle
metabolism, and hydration status.
2-Serum creatinine concentrations may not
change until about 50% of kidney function has
already been lost.
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17. Serum creatinine for AKI
3-At lower rates of glomerular filtration, the
amount of tubular secretion of creatinine
results in overestimation of renal function.
4-During acute changes in glomerular filtration,
serum creatinine does not accurately depict
kidney function until steady-state equilibrium
has been reached, which may require several
days , so there is relatively slow kinetics after
injury.
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18. Serum creatinine for AKI
So , Inherent problems with SCr as ARF
marker
–Does not differentiate
The nature and type of renal insult
Site of renal insult
–Changes in SCr may lag changes in GFR
and may be a very late indicator of renal
injury3/7/2020 4:56 AM 18

19. Biomarkers for Acute Kidney
Injury
• Ideally A IL-18 KI better to have a biomarker like
myocardial infarction
– (i.e. troponin-1)
• Currently no Troponin-I like marker to identify the site
or severity of injury, although various markers are
being evaluated
– Neutrophil gelatinase-associated lipocalcin (NGAL)
– Cystatin C
– IL-18
– Kidney Injury Molecule (KIM-1)
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20. Utilities of biomarkers in AKI
 Early diagnosis
 Define severity of injury, monitor AKI course
 Define AKI subtypes & etiology (pre-renal, septic,
nephrotoxic)
 Monitor response to AKI interventions
 Risk stratify for poor outcomes (dialysis need, CKD,
mortality)
 Identify location of renal tubular injury
Devarajan & Williams, Seminars in Nephrol, 2007
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21. What is an ideal biomarker?
Qualities
 Accurate, reliable
 Relatively non-
invasive/acceptable to
patients
 Rapidly measurable,
standardized assay
 Sensitive/specific with
reproducible cutoff values
Nguyen & Devarajan, Ped Nephrol, 2008
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22. Phases of biomarker discovery: bench
to bedside
Phases of biomarker development
Phase Terminology Action Steps
Phase 1 Preclinical Discovery • Discover biomarkers in tissues or body fluids
• Confirm and prioritize promising candidates
Phase 2 Assay Development • Develop and optimize clinically useful assay
• Test on existing samples of established disease
Phase 3 Retrospective Study • Test biomarker in completed clinical trial
• Test if biomarker detects the disease early
• Evaluate sensitivity, specificity, ROC
Phase 4 Prospective Screening • Use biomarker to screen population
• Identify extent and characteristics of disease
• Identify false referral rate
Phase 5 Disease Control • Determine impact of screening on reducing
disease burden
Devarajan & Williams, Seminars Nephrol, 2007; Coca & Parikh, CJASN, 2008
DiscoveryTranslationalValidation
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23. Biomarker discovery in AKI:
bench to bedside
NGAL( proximal tubule lysosomal enzyme)
– Expressed in proximal and distal nephron
– Binds and transports iron-carrying molecules
– An important function of NGAL under physiological
conditions is to act as bacteriostatic agent ,chemoattractant
for neutrophils and as an inhibitor of cellular oxidative
stress
– Rises very early (hours) after injury in animals, confirmed
in children having CPB
– The NGAL protein found in proximal tubules after
ischemic injury is proposed to be derived from glomerular
filtration of circulating NGAL synthesized by other organs
like liver
– Following ischemic injury, NGAL levels in the kidney3/7/2020 4:56 AM 23

24. Cystatin-C (Cys-C cysteine protease inhibitor):
– Freely filtered by the glomerulus, reabsorbed and
catabolized, but not secreted by the tubules
– Cystatin C is produced at a constant rate by nucleated cells.
– Urinary Cys-C levels have been found to be elevated in
individuals with known tubular dysfunction
– Its concentration is not influenced by infections, liver
diseases, or inflammatory diseases.
– It has also been shown that a 50% increase in cystatin C
can predict AKI 48 hours before the rise in serum
creatinine and obviously before any forms of creatinine
clearance measurements
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25. 2 4 6 8 12 24 36 48 60 72 84 96 108 120
Post CPB Time (hours)
UrineNGAL(ng/ml)
No ARF
(n=51)
ARF
(n=20)
Serum Creatinine Rise
Detection of Urinary NGAL by ELISA
Urine NGAL is upregulated 15-fold within 2 hours after CPB in patients who later develop ARF
Mishra J et al: Lancet 2005
1514131211109876543210
25
50
75
100
125
150
175
200
225
25

26. Cardiac surgery: Known timing of AKI
NGAL: Children led the way! Mishra et al, Lancet, 2005
SCr rise
48-72 hrs
Wagener et al, Anesthesiology, 2006
Adults
Not quite as good
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27. Cardiac surgery
Parikh et al,KI, 2006
Children
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28. • 140 patients’ urine samples available
• Mean age 6.3 years (1 year to 21 years)
• Mean ICU day of admission = 3 + 1.5 days
• pRIFLE
– No AKI: 24.3%
– Risk : 33.7%
– Injury : 22.1%
– Failure: 17.9%
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29. 3/7/2020 4:56 AM 29

30. Current status of promising acute kidney injury
(AKI) biomarkers in various clinical situations
NoneNot TestedNot testedNot testedIntermediateUrineKIM-1
NoneIntermediateIntermediateAbsentIntermediateUrineIL-18
AbbottaEarlyEarlyEarlyEarlyUrineNGAL
Dade-BehringIntermediateIntermediateIntermediateIntermediatePlasmaCystatin C
BiositeaEarlyEarlyEarlyEarlyPlasmaNGAL
Commercial Test?
Kidney
Transplant
Sepsis or ICU
Contrast
Nephropathy
Cardiac Surgery
Sample
Source
Biomarker
Name
NGAL neutrophil gelatinase-associated lipocalin, IL-18 interleukin 18, KIM-1 kidney injury molecule 1
aIn development3/7/2020 4:56 AM 30

31. Serum creatinine of the patients at baseline (pre-
operative), 6 hours, 24 hours and 48 hours post-
CPB
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0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Baseline After 6 h After 24 h After 48 h
Meanofcreatinine

32. 3/7/2020 4:56 AM 32
ROC curve for NGAL 6 hours after CPB ROC curve for NGAL 24 hours after CPB

33. Conclusions
 Since AKI increases mortality rate and significantly
worsens patients’ outcome, it is important to determine the
patient with risk for AKI in ICU.
 Earlier recognition and treatment of AKI sequelae may
improve outcome
 Every patient who is admitted to the ICU should be
evaluated and categorized based on the creatinine level.
 Furthermore, close follow-up of renal function is crucial.
Recently introduced biomarkers can be used for early
diagnosis of AKI even before SCr level starts to increase.
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34. Thank You
Questions?
34