a b s t r a c t

Objective: Copeptin, reflecting vasopressin release, as well as the National Early Warning Score , reflecting the severity of critical illness, might qualify for survival prediction in elderly patients with critical illness. This pro- spective observational study aims at assessing the predictive value of copeptin combined with NEWS on the prognosis of elderly critical ill patients at emergency department (ED).

Methods: We analyzed serum copeptin levels and the NEWS at admission to the ED in a prospective, single- center, and observational study comprising 205 elderly patients with critical illness. Death within 30 days after admission to the ED was the primary end point.

Results: The serum copeptin levels and the NEWS in the non-survivor patients group were higher than those in the survivor group [30.35 (14.20, 38.91) vs 17.53 (13.01, 25.20), P = 0.001 and 9.0 (7.0-10.0) vs 7.0 (6.0-8.0),

P = 0.001]. Multivariate logistic regression analysis showed that copeptin, NEWS and copeptin combined with NEWS were all independent risk factors for 30-day mortality in elderly patients with critical illness. Copeptin, NEWS and copeptin combined with NEWS all performed well in predicting 30-day survival, with area under the ROC curve (AUC) values of 0.766 (95%CI, 0.702-0.822), 0.797 (95%CI, 0.744-0.877) and 0.854 (95%CI,

0.798-0.899) respectively. Using the Z test to compare the areas under the above three curves, copeptin com- bined with NEWS showed a higher predictive value for 30-day survival (P < 0.05). As we calculated, the optimal cut-off values of copeptin and NEWS using the Youden index were 19.78 pg/mL and 8.5 points, respectively. Risk stratification analysis showed that patients with both copeptin levels higher than 19.78 pg/mL and NEWS points higher than 8.5 points had the highest risk of death.

Conclusions: Copeptin combined with NEWS have a stronger Predictive power on the prognosis of elderly pa- tients with critical illness at ED, comparing to either factor individually.

(C) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://

creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction

Vasopressin, also known as arginine vasopressin (AVP) or anti- diuretic hormone (ADH), plays a key role in many physiologic and path- ologic processes, such as changes in blood pressure, volume, and plasma osmolality [1,2]. AVP is released into the circulation in response to var- ious stimuli, which usually signal disturbances in body homeostasis and stress. Therefore, the release of AVP is not specific for a single pathologic or physiological condition but encompasses a broad spectrum of entities [3]. Despite its pivotal role in maintaining body homeostasis under physiological and pathophysiological conditions, the reliable measure- ment of AVP has never reached clinical practicability, due to consider- able technical challenges related to AVP’s short plasma half-life, interaction with platelets in the serum, and biochemical instability [1,2].

* Corresponding author.

E-mail address: [email protected] (X. Zhang).

Copeptin, a 39-aminoacid glycopeptide, is a C-terminal part of the precursor pre-provasopressin (pre-proAVP), which consists of a signal peptide, AVP, neurophysin II, and copeptin (Fig. 1) [4]. Thus, copeptin is released in equimolar amounts together with AVP during precursor processing. In contrast to AVP, copeptin is very stable in the serum or plasma at Room temperature and is easy to measure [5,6]. The current research has shown that copeptin reliably mirrors biologically function- ality of AVP under diverse physiologic and pathophysiologic conditions such as changes in plasma osmolality and various Disease states [7-9]. Therefore, copeptin as an adjuvant biomarker may help in stratifying patients at risk as well as in prognosis [10-13].

Back in 2012, the UK Royal College of Physicians developed the Na- tional Early Warning Score (NEWS), a simple and easy to use tool at the bedside, which has become a common tool for predicting deteriora- tion in the emergency patients, and commonly used internationally [14,15]. In this study, we aimed to evaluate whether copeptin combined with NEWS have a stronger predictive power on the prognosis of elderly

https://doi.org/10.1016/j.ajem.2021.05.052

0735-6757/(C) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Fig. 1. Structure of pre-provasopressin.

patients with critical illness at emergency department (ED), which was never reported previously.

1. Materials and methods
   1. Subjects and study design

We conducted a prospective observational study of consecutive pa- tients admitted to the ED of a single academic tertiary hospital between January 2017 and November 2018. We included patients aged over 60 at admission to the ED who had NEWS (Table 1) of 5 points or more. The following patients were excluded: patients with trauma; patients with immunodeficiency or autoimmune diseases; patients with end-stage renal disease or end-stage liver disease; patients with advanced malig- nant tumor; patients for end-of-life or hospice care. The study was ap- proved by the ethical review board at Beijing Hospital. A written informed consent was obtained from all participants.

• 1. Baseline assessment and follow-up

On admission to the ED, patients’ demographic data, medical/medi- cation history and vital signs were recorded, and the NEWS were calcu- lated. A separate blood tube for copeptin analysis was included in the standardized laboratory panel, routinely collected within few minutes from ED admission. Routine laboratory tests include complete blood count, creatinine, urea nitrogen, aminotransferase, procalcitonin, car- diac troponin I and N-terminal pro-B-type natriuretic peptide.

Follow-up was performed for 30 days or until death, whichever oc- curred first. Patients alive at day 30 were classified as survivors; all others were classified as non-survivors. No patient was lost to follow-up.

• 1. Copeptin measurements

Venous blood samples were collected at the time of admission, cen- trifuged, and serum samples were stored at -80 ?C. Copeptin concen- trations were analyzed by enzyme-linked immunosorbent assay (ELISA) using commercial kits (Beijing Solarbio Science & Technology Co., Ltd., Beijing, China) in accordance with the manufactures’ instructions.

• 1. Statistical analysis

Normally distributed continuous variables were described using mean +- standard deviation (SD), non-normally distributed continuous variables as median and interquartile range (IQR). Categorical variables

were described as frequency or percentage and tested by Chi-squared test. The relation of predictors with survival was investigated using lo- gistic regression models. The prognostic values of copeptin, NEWS and copeptin combined with NEWS on the outcome were evaluated by Re- ceiver Operating Characteristic (ROC) curve which compared by Z-test, and the Youden index was used to identify the optimal cut-off points for risk stratification. The area under the ROC curve (AUC) values were re- ported with corresponding 95% (confidence intervals) CIs. All tests were 2-tailed; P<0.05 was defined as significant. Data were analyzed using statistical software programs (SPSS, Ver. 23.0; MedCalc, Ver. 18.0).

1. Results
   1. Baseline characteristics

A total of 205 patients were included in the study, 128 patients with cardiovascular critical illness, 39 patients with respiratory critical ill- ness, 26 patients with sepsis, 12 patients with other critical illness (in- cluding gastrointestinal bleeding, rhabdomyolysis, organophosphorus poisoning, and anaphylactic shock). Within 30 days after admission, 159 patients (77.6%) alive at day 30 were classified as survivors, 46 pa- tients (22.4%) were classified as non-survivors. Baseline characteristics, serum copeptin levels and the NEWS were compared between survivor group and non-survivor group (Table 2). The serum copeptin levels and the NEWS in the non-survivor group were higher than those in the sur- vivor group (30.35 (14.20, 38.91), 17.53 (13.01, 25.20), P = 0.001; 9.0

(7.0-10.0), 7.0 (6.0-8.0), P = 0.001)).

• 1. Independent predictors of 30-day survival in elderly patients with crit- ical illness

Multivariate logistic regression analyses were performed using variables including copeptin, NEWS, MBP, ALT, AST, CRE, cTNI and

Table 2

Clinical and demographic baseline characteristics of the study population.

	Non-survivors (n = 46)	Survivors (n = 159)	P-value
Age (years)	80.5(73.8-86.0)	79.0(72.3-85.8)	0.051
Male Gender, n (%)	23 (50.0)	91 (57.2)	0.404
cTnI (ng/mL)	0.230(0.028-0.845)	0.049(0.013-0.287)	0.006
NT-proBNP	12,395	4819	0.001
(pg/mL)	(3000.9-29,136.6)	(1364.3-13,416.0)
CRE (umol/L)	110.5(75.5-145.3)	92.5(75.0-149.0)	0.001
ALT (U/L)	30.0(13.0-136.3)	24.0(17.3-45.3)	0.348
AST (U/L)	39.5(17.5-114.0)	23.0(15.0-38.0)	0.016
MBP (mmHg)	68(56-95)	96(80-106)	0.017
PLT (x109 /L)	187(151.5-251.3)	165(140.3-224.3)	0.768
PCT (ng/mL)	3.26(0.85-27.84)	0.31(0.05-3.98)	0.001
NEWS (points)	9.0(7.0-10.0)	7.0(6.0-8.0)	0.001
Copeptin (pg/mL)	30.35(14.20-38.91)	17.53(13.01-25.20)	0.001

Values were given as numbers (%) or median (IQR).

cTNI, cardiac troponin I; NT-proBNP, N-terminal pro-B-type natriuretic peptide; CRE, cre- atinine; ALT, alanine aminotransferase; AST, aspartate aminotransferase; MBP, mean arte- rial pressure; PLT, platelet; PCT, procalcitonin.

Table 1

The National Early Warning Score .

Physiological parameters	3	2	1	0	1	2	3
Respiration rate (min-1) Oxygen saturation (%)	<=8 <=91	92-93	9-11 94-95	12-20 >=96		21-24	>=25
Any supplemental oxygen		Yes		No
Temperature (?C) Systolic blood pressure (mmHg)	<=35.0 <=90	91-100	35.1-36.0 101-110	36.1-38.0 111-219	38.1-39.0	>=39.1	>=220
Heart rate (min-1) Level of consciousness a	<=40		41-50	51-90 A	91-110	111-130	>=131 V, P, U

^a A = alert, V = verbal, P = pain, U = unresponsive.

Predictive performance of copeptin,”>Table 3

Regression analysis of copeptin and NEWS in elderly patients with critical illness.

Table 5

The comparison of the AUC of copeptin, NEWS and copeptin combined with NEWS.

B		SE	Wald	P-value	Exp(B)	95%CI Exp(B)				Index	SE	Z	P-value	95%CI Exp(B)
						Lower	Upper							Lower	Upper
Copeptin	0.047	0.014	11.491	0.001	1.049	1.020	1.078			Copeptin/NEWS	0.059	0.654	0.512	-0.077	0.155
NEWS	0.569	0.106	28.704	0.001	1.767	1.435	2.175			Copeptin/combine	0.043	2.024	0.043	0.003	0.173
Constant	-6.677	0.925	52.057	0.001	0.001	-				NEWS/ combine	0.022	2.263	0.024	0.007	0.092

NT-proBNP, showed that copeptin and NEWS were both independent predictors of 30-day survival in elderly patients with critical illness (Table 3). In further analysis, copeptin combined with NEWS was also an independent predictor of 30-day survival in elderly patients with critical illness.

• 1. Predictive performance of copeptin, NEWS and copeptin combined with NEWS

Copeptin, NEWS and copeptin combined with NEWS all showed a good performance for predicting 30-day survival in elderly patients

with critical illness, with the AUC values of 0.766 (95%CI, 0.702- 0.822), 0.797 (95%CI, 0.744-0.877) and 0.854 (95%CI, 0.798-0.899)

(Fig. 2, Table 4). Using Z-test to compare the above three curves, copeptin combined with NEWS had a higher predictive value for 30-day survival (P < 0.05) (Table 5). The optimal cut-off values of copeptin and NEWS for predicting mortality were 19.78 pg/mL and

8.5 points respectively using Youden index. Risk stratification analyses showed that patients with copeptin levels higher than 19.78 pg/mL in addition NEWS points higher than 8.5 points had the highest risk of death (Fig. 3). Copeptin combined with NEWS had a stronger predictive power on the prognosis of elderly patients with critical illness.

Fig. 2. The ROC curve of copeptin, NEWS and copeptin combined with NEWS.

Table 4

The area under the ROC curve of copeptin, NEWS and copeptin combined with NEWS.

	AUC	SE	Sensitivity (%)	Specificity (%)	P-value	Cut-off value	95%CI
							Lower	Upper
Copeptin	0.766	0.046	69.6	81.8	0.001	19.78	0.702	0.822
NEWS	0.797	0.040	59.0	90.0	0.002	8.5	0.744	0.877
Copeptin combined with NEWS	0.854	0.033	83.0	72.0	0.001		0.798	0.899

Fig. 3. Risk stratification according to the optimal cut-off values of copeptin and NEWS.

90

80

70

60

50

40

30

20

10

0

>=8.5,83.3

>=8.5,36.8

?8.5,32.4

?8.5,5.6

>=8.5 ?8.5

NEWS point

copeptin?19.78 copeptin>=19.78

1. Discussion

30-day mortality(%)

Survival prediction in ED is critical to detecting early signs of clinical deterioration and enabling a timely and appropriate clinical interven- tion. Accurate diagnosis and treatment may be delayed in elderly pa- tients because they present with atypical signs and symptoms, use several medications, and have Multiple comorbidities, which makes survival prediction difficult [16]. The Basel Non-specific Complaints (BANC) study [17] was a delayed type of cross-sectional diagnostic study with a prospective 30-day follow-up showing that sensitive risk stratification tools were needed to identify whether the patients with Nonspecific complaints presenting to the ED had potentially adverse health outcomes.

In recent years, as a research hotspot, copeptin has exhibited early diagnosis, Severity assessment and survival prognostic abilities in vari- ous patient cohorts, such as acute coronary syndrome, decompensated heart failure, acute exacerbation of chronic obstructive disease, sepsis, and trauma [18-24]. Copeptin is triggered by many diseases, not limited to one single organ system. Its non-specificity, with respect to a precise diagnostic role, is its strength as a more generalized marker for acute critical illness [25]. In a prospective observational single-center study including 225 critically ill patients admitted to a medical ICU [26], non-survivors within 30 days after ICU admittance showed significantly higher circulating copeptin levels as compared to survivors. Circulating levels of copeptin at ICU admission independently predicted 30-day mortality in patients admitted to a medical ICU. In our study, we con- firmed the value of copeptin as a short-term Prognostic biomarker in el- derly patients with critical illness. The serum copeptin levels were significantly higher in non-survivors as compared with survivors. Mul- tivariate logistic regression analysis showed that copeptin was an inde- pendent risk factor for 30-day mortality in elderly patients with critical illness. Therefore, copeptin may well be a clinically useful non-specific prognostic marker reflecting disease severity and survival, with no ex- ception in elderly patients.

Thus far the NEWS is the most sensitive Early Warning Score avail- able in emergency patients. NEWS has been found to have the best dis- criminative ability for death within 24 h or a combined endpoint of cardiac arrest, unanticipated ICU admission, and 24 h mortality

compared with 33 other EWS systems [27]. A retrospective observa- tional cohort study [28] with 81,520 consecutive ED patients concluded that the NEWS could predict in-hospital mortality within 24 h, 48 h, 7 days, and 30 days for patients arriving at the ED. In our study, median NEWS points were significantly higher in non-survivors as compared with survivors. Multivariate logistic regression analysis showed that NEWS was independent risk factors for 30-day mortality in elderly pa- tients with critical illness. Therefore, the performance of NEWS to pre- dict mortality for emergency elderly patients was also valid and reliable. However, NEWS is not suitable for all patients [29]. For patients with cardiovascular diseases, the discrimination of NEWS to predict mortality was not so good [30]. Several studies have combined NEWS with lactate, d-dimer, or routine blood tests to improve its effectiveness of predicting mortality in ED patients [31-34]. From our multivariate logistic regres- sion analysis, copeptin combined with NEWS were also an independent risk factor for 30-day mortality in elderly patients with critical illness. In the further study, copeptin combined with NEWS showed a better per- formance for predicting 30-day survival in elderly patients with critical illness, with the AUC values of 0.854 (95%CI, 0.798-0.899), comparing to copeptin or NEWS individually. Importantly, we calculated the optimal cut-off values of copeptin and NEWS for predicting mortality using the Youden index. Risk stratification analysis showed that patients with copeptin levels higher than 19.78 pg/mL in addition NEWS points higher than 8.5 points had the highest risk of death. Therefore, our study concluded that copeptin combined with NEWS have a stronger predictive power on the prognosis of elderly patients with critical

illness.

1. Limitations

This study has potential limitations. First, our data were collected at a single centre, and the sample size was relatively small, which limits their applicability to other populations of critical illness patients. Sec- ond, copeptin and NEWS were collected immediately after the patients came to the ED, and we did not monitor and analyze the dynamic changes of copeptin and NEWS. These limitations will be compensated and improved in our further research.

1. Conclusions

Copeptin combined with NEWS have a stronger predictive power on the prognosis of elderly patients with critical illness at ED, comparing to either factor individually.

Statement

This study occurred before the COVID-19 epidemic in China. There- fore, patients with covid-19 were not included in the study.

Declaration of Competing Interest

We declare that we have no conflict of interest.

Appendix A. Supplementary data

Supplementary data to this article can be found online at https://doi. org/10.1016/j.ajem.2021.05.052.

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