Introduction: C-reactive protein-to-albumin ratio (CAR) is a prognostic marker in various diseases that represents patients’ inflammation and nutritional status. Here, we aimed to investigate the prognostic value of CAR in critically ill patients with severe acute kidney injury requiring continuous renal replacement therapy (CRRT). Methods: We retrospectively collected data from eight tertiary hospitals in Korea from 2006–2021. The patients were divided into quartiles according to CAR levels at the time of CRRT initiation. Cox regression analyses were performed to investigate the effect of CAR on in-hospital mortality. The mortality prediction performance of CAR was evaluated using the area under the curve (AUC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI). Results: In total, 3,995 patients who underwent CRRT were included, and the in-hospital mortality rate was 67.3% during the follow-up period. The 7-day, 30-day, and in-hospital mortality rates increased toward higher CAR quartiles (all p < 0.001). After adjusting for confounding variables, the higher quartile groups had an increased risk of in-hospital mortality (quartile 3: adjusted hazard ratio [aHR], 1.26, 95% confidence interval [CI], 1.10–1.43, p < 0.001; quartile 4: aHR, 1.22, 95% CI, 1.07–1.40, p = 0.003). CAR combined with Acute Physiology and Chronic Health Evaluation II or Sequential Organ Failure Assessment scores significantly increased the predictive power compared to each severity score alone for AUC, NRI, and IDI (all p < 0.05). Conclusions: A high CAR is associated with increased in-hospital mortality in critically ill patients requiring CRRT. The combined use of CAR and severity scores provides better predictive performance for mortality than the severity score alone.

The mortality rate of critically ill patients with severe acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT) remains high. In addition, predicting the prognosis of these patients, which is crucial for determining the appropriate treatment level and timing, is difficult. Herein, we evaluated the C-reactive protein-to-albumin ratio (CAR) as a prognostic factor and compared its predictive performance with those of traditional severity scores. Our study demonstrated that high CAR was associated with increased in-hospital mortality. In particular, the addition of CAR to the APACHE II and SOFA scores was superior to traditional severity scores alone in predicting mortality. Consequently, CAR can be used to enhance the accuracy of predicting mortality in patients with severe AKI who require CRRT.

1.
Lameire
NH
,
Bagga
A
,
Cruz
D
,
De Maeseneer
J
,
Endre
Z
,
Kellum
JA
.
Acute kidney injury: an increasing global concern
.
Lancet
.
2013
;
382
(
9887
):
170
9
.
2.
Siew
ED
,
Davenport
A
.
The growth of acute kidney injury: a rising tide or just closer attention to detail
.
Kidney Int
.
2015
;
87
(
1
):
46
61
.
3.
Hoste
EA
,
Bagshaw
SM
,
Bellomo
R
,
Cely
CM
,
Colman
R
,
Cruz
DN
.
Epidemiology of acute kidney injury in critically ill patients: the multinational AKI-EPI study
.
Intensive Care Med
.
2015
;
41
(
8
):
1411
23
.
4.
Wald
R
,
McArthur
E
,
Adhikari
NK
,
Bagshaw
SM
,
Burns
KE
,
Garg
AX
.
Changing incidence and outcomes following dialysis-requiring acute kidney injury among critically ill adults: a population-based cohort study
.
Am J Kidney Dis
.
2015
;
65
(
6
):
870
7
.
5.
Park
S
,
Lee
S
,
Jo
HA
,
Han
K
,
Kim
Y
,
An
JN
.
Epidemiology of continuous renal replacement therapy in Korea: results from the national health insurance service claims database from 2005 to 2016
.
Kidney Res Clin Pract
.
2018
;
37
(
2
):
119
29
.
6.
Prowle
JR
,
Bellomo
R
.
Continuous renal replacement therapy: recent advances and future research
.
Nat Rev Nephrol
.
2010
;
6
(
9
):
521
9
.
7.
Stads
S
,
Fortrie
G
,
van Bommel
J
,
Zietse
R
,
Betjes
MG
.
Impaired kidney function at hospital discharge and long-term renal and overall survival in patients who received CRRT
.
Clin J Am Soc Nephrol
.
2013
;
8
(
8
):
1284
91
.
8.
Wu
VC
,
Shiao
CC
,
Chi
NH
,
Wang
CH
,
Chueh
SCJ
,
Liou
HH
.
Outcome prediction of acute kidney injury biomarkers at initiation of dialysis in critical units
.
J Clin Med
.
2018
;
7
(
8
):
202
.
9.
Jo
SK
,
Yang
J
,
Hwang
SM
,
Lee
MS
,
Park
SH
.
Role of biomarkers as predictors of acute kidney injury and mortality in decompensated cirrhosis
.
Sci Rep
.
2019
;
9
(
1
):
14508
.
10.
Chen
YT
,
Jenq
CC
,
Hsu
CK
,
Yu
YC
,
Chang
CH
,
Fan
PC
.
Acute kidney disease and acute kidney injury biomarkers in coronary care unit patients
.
BMC Nephrol
.
2020
;
21
(
1
):
207
.
11.
Lim
JH
,
Jeon
Y
,
Ahn
JS
,
Kim
S
,
Kim
DK
,
Lee
JP
.
GDF-15 predicts in-hospital mortality of critically ill patients with acute kidney injury requiring continuous renal replacement therapy: a multicenter prospective study
.
J Clin Med
.
2021
;
10
(
16
):
3660
.
12.
Schaefer
JH
,
Jochimsen
F
,
Keller
F
,
Wegscheider
K
,
Distler
A
.
Outcome prediction of acute renal failure in medical intensive care
.
Intensive Care Med
.
1991
;
17
(
1
):
19
24
.
13.
Halstenberg
WK
,
Goormastic
M
,
Paganini
EP
.
Validity of four models for predicting outcome in critically ill acute renal failure patients
.
Clin Nephrol
.
1997
;
47
(
2
):
81
6
.
14.
Demirjian
S
,
Chertow
GM
,
Zhang
JH
,
O’Connor
TZ
,
Vitale
J
,
Paganini
EP
.
Model to predict mortality in critically ill adults with acute kidney injury
.
Clin J Am Soc Nephrol
.
2011
;
6
(
9
):
2114
20
.
15.
Kim
Y
,
Park
N
,
Kim
J
,
Kim
DK
,
Chin
HJ
,
Na
KY
.
Development of a new mortality scoring system for acute kidney injury with continuous renal replacement therapy
.
Nephrology
.
2019
;
24
(
12
):
1233
40
.
16.
Pepys
MB
,
Hirschfield
GM
.
C-reactive protein: a critical update
.
J Clin Invest
.
2003
;
111
(
12
):
1805
12
.
17.
Lau
DC
,
Dhillon
B
,
Yan
H
,
Szmitko
PE
,
Verma
S
.
Adipokines: molecular links between obesity and atheroslcerosis
.
Am J Physiol Heart Circ Physiol
.
2005
288
5
H2031
41
.
18.
Eckart
A
,
Struja
T
,
Kutz
A
,
Baumgartner
A
,
Baumgartner
T
,
Zurfluh
S
.
Relationship of nutritional status, inflammation, and serum albumin levels during acute illness: a prospective study
.
Am J Med
.
2020
;
133
(
6
):
713
22.e7
.
19.
Gupta
A
,
Gupta
E
,
Hilsden
R
,
Hawel
JD
,
Elnahas
AI
,
Schlachta
CM
.
Preoperative malnutrition in patients with colorectal cancer
.
Can J Surg
.
2021
64
6
E621
29
.
20.
Ranzani
OT
,
Zampieri
FG
,
Forte
DN
,
Azevedo
LC
,
Park
M
.
C-reactive protein/albumin ratio predicts 90-day mortality of septic patients
.
PLoS One
.
2013
;
8
(
3
):
e59321
.
21.
Oh
TK
,
Ji
E
,
Na
HS
,
Min
B
,
Jeon
YT
,
Do
SH
.
C-reactive protein to albumin ratio predicts 30-day and 1-year mortality in postoperative patients after admission to the intensive care unit
.
J Clin Med
.
2018
;
7
(
3
):
39
.
22.
Wang
J
,
Zhao
K
,
Mao
X
,
Zhang
Y
,
Shao
J
,
Fan
W
.
Relationship between CRP albumin ratio and the mortality in critically ill patients with AKI: a retrospective observational study
.
Biomed Res Int
.
2021
;
2021
:
9957563
.
23.
Amygdalos
I
,
Bednarsch
J
,
Meister
FA
,
Erren
D
,
Mantas
A
,
Strnad
P
.
Clinical value and limitations of the preoperative C-reactive-protein-to-albumin ratio in predicting post-operative morbidity and mortality after deceased-donor liver transplantation: a retrospective single-centre study
.
Transpl Int
.
2021
;
34
(
8
):
1468
80
.
24.
Charlson
ME
,
Pompei
P
,
Ales
KL
,
MacKenzie
CR
.
A new method of classifying prognostic comorbidity in longitudinal studies: development and validation
.
J Chronic Dis
.
1987
;
40
(
5
):
373
83
.
25.
Khwaja
A
.
KDIGO clinical practice guidelines for acute kidney injury
.
Nephron Clin Pract
.
2012
120
4
c179
84
.
26.
Bone
RC
,
Balk
RA
,
Cerra
FB
,
Dellinger
RP
,
Fein
AM
,
Knaus
WA
.
Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. The ACCP/SCCM consensus conference committee. American college of chest physicians/society of critical care medicine
.
Chest
.
1992
;
101
(
6
):
1644
55
.
27.
DeLong
ER
,
DeLong
DM
,
Clarke-Pearson
DL
.
Comparing the areas under two or more correlated receiver operating characteristic curves: a nonparametric approach
.
Biometrics
.
1988
;
44
(
3
):
837
45
.
28.
Póvoa
P
,
Coelho
L
,
Almeida
E
,
Fernandes
A
,
Mealha
R
,
Moreira
P
.
C-reactive protein as a marker of infection in critically ill patients
.
Clin Microbiol Infect
.
2005
;
11
(
2
):
101
8
.
29.
Schmit
X
,
Vincent
JL
.
The time course of blood C-reactive protein concentrations in relation to the response to initial antimicrobial therapy in patients with sepsis
.
Infection
.
2008
;
36
(
3
):
213
9
.
30.
Tan
M
,
Lu
Y
,
Jiang
H
,
Zhang
L
.
The diagnostic accuracy of procalcitonin and C-reactive protein for sepsis: a systematic review and meta-analysis
.
J Cell Biochem
.
2019
;
120
(
4
):
5852
9
.
31.
Kianfar
E
.
Protein nanoparticles in drug delivery: animal protein, plant proteins and protein cages, albumin nanoparticles
.
J Nanobiotechnology
.
2021
;
19
(
1
):
159
.
32.
Oliveira
EA
,
Zheng
R
,
Carter
CE
,
Mak
RH
.
Cachexia/Protein energy wasting syndrome in CKD: causation and treatment
.
Semin Dial
.
2019
;
32
(
6
):
493
9
.
33.
Phillips
A
,
Shaper
AG
,
Whincup
PH
.
Association between serum albumin and mortality from cardiovascular disease, cancer, and other causes
.
Lancet
.
1989
;
2
(
8677
):
1434
6
.
34.
Wilson
AM
,
Ryan
MC
,
Boyle
AJ
.
The novel role of C-reactive protein in cardiovascular disease: risk marker or pathogen
.
Int J Cardiol
.
2006
;
106
(
3
):
291
7
.
35.
Al-Subaie
N
,
Reynolds
T
,
Myers
A
,
Sunderland
R
,
Rhodes
A
,
Grounds
RM
.
C-reactive protein as a predictor of outcome after discharge from the intensive care: a prospective observational study
.
Br J Anaesth
.
2010
;
105
(
3
):
318
25
.
36.
Gupta
D
,
Lis
CG
.
Pretreatment serum albumin as a predictor of cancer survival: a systematic review of the epidemiological literature
.
Nutr J
.
2010
;
9
:
69
.
37.
Hart
PC
,
Rajab
IM
,
Alebraheem
M
,
Potempa
LA
.
C-reactive protein and cancer-diagnostic and therapeutic insights
.
Front Immunol
.
2020
;
11
:
595835
.
38.
Pierrakos
C
,
Vincent
JL
.
Sepsis biomarkers: a review
.
Crit Care
.
2010
14
1
R15
.
39.
Pierrakos
C
,
Velissaris
D
,
Bisdorff
M
,
Marshall
JC
,
Vincent
JL
.
Biomarkers of sepsis: time for a reappraisal
.
Crit Care
.
2020
;
24
(
1
):
287
.
40.
Park
JE
,
Chung
KS
,
Song
JH
,
Kim
SY
,
Kim
EY
,
Jung
JY
.
The C-reactive protein/albumin ratio as a predictor of mortality in critically ill patients
.
J Clin Med
.
2018
;
7
(
10
):
333
.
41.
Bilgin
S
,
Kurtkulagi
O
,
Atak Tel
BM
,
Duman
TT
,
Kahveci
G
,
Khalid
A
.
Does C-reactive protein to serum Albumin Ratio correlate with diabEtic nephropathy in patients with Type 2 dIabetes MEllitus? The CARE TIME study
.
Prim Care Diabetes
.
2021
;
15
(
6
):
1071
4
.
42.
Demirkol
ME
,
Alisik
M
,
Yis
OM
.
C-reactive protein to albumin ratio in patients with prediabetes and diabetes mellitus: HbA1c and inflammation
.
Clin Lab
.
2022
;
68
(
8
):
68
.
43.
Vincent
JL
,
Moreno
R
,
Takala
J
,
Willatts
S
,
De Mendonça
A
,
Bruining
H
.
The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. On behalf of the working group on sepsis-related problems of the European society of intensive care medicine
.
Intensive Care Med
.
1996
;
22
(
7
):
707
10
.
44.
Knaus
WA
,
Draper
EA
,
Wagner
DP
,
Zimmerman
JE
.
Apache II: a severity of disease classification system
.
Crit Care Med
.
1985
;
13
(
10
):
818
29
.
45.
Li
J
,
Li
Y
,
Sheng
X
,
Wang
F
,
Cheng
D
,
Jian
G
.
Combination of mean platelet volume/platelet count ratio and the Apache II score better predicts the short-term outcome in patients with acute kidney injury receiving continuous renal replacement therapy
.
Kidney Blood Press Res
.
2018
;
43
(
2
):
479
89
.
46.
Kang
MW
,
Kim
J
,
Kim
DK
,
Oh
KH
,
Joo
KW
,
Kim
YS
.
Machine learning algorithm to predict mortality in patients undergoing continuous renal replacement therapy
.
Crit Care
.
2020
;
24
(
1
):
42
.
47.
Järvisalo
MJ
,
Hellman
T
,
Uusalo
P
.
Mortality and associated risk factors in patients with blood culture positive sepsis and acute kidney injury requiring continuous renal replacement therapy-A retrospective study
.
PLoS One
.
2021
;
16
(
4
):
e0249561
.
48.
Kang
MW
,
Tangri
N
,
Kwon
S
,
Li
L
,
Lee
H
,
Han
SS
.
Development of new equations predicting the mortality risk of patients on continuous RRT
.
Kidney360
.
2022
;
3
(
9
):
1494
501
.
49.
Lim
JH
,
Chung
BH
,
Lee
SH
,
Jung
HY
,
Choi
JY
,
Cho
JH
.
Omics-based biomarkers for diagnosis and prediction of kidney allograft rejection
.
Korean J Intern Med
.
2022
;
37
(
3
):
520
33
.
You do not currently have access to this content.