Investigation of the relationship between vascular events and copeptin levels in hospitalized COVID-19 patients

Introduction

Coronavirus disease 2019 (COVID-19) is a viral disease with a high fatality rate. This disease is caused by the novel coronavirus, SARS-CoV-2 [1]. Although most patients have a mild clinical course, some patients experience more serious complications, such as cardiovascular diseases, which require treatment in the intensive care unit (ICU) [2]. Hypertension, arrhythmias, cardiomyopathy, and coronary heart disease are among the major comorbid cardiovascular diseases observed in patients with severe COVID-19 [3].

Copeptin, the C-terminal component of vasopressin precursor, is a glycopeptide consisting of 39 amino acids. Vasopressin’s problems with stability in human serum and plasma have led to the development of copeptin as a substitute indicator since it is secreted at equimolar levels [4], 5]. Measuring arginine vasopressin (AVP) levels is technically challenging owing to its small particle size, short half-life, and interaction with thrombocytes. Measurement of plasma copeptin levels is a more practical approach and can be utilized to quantify AVP activity [6]. On the other hand, copeptin has a more stable peptide structure, and its blood levels are simple to measure [7].

While clinical status, oxygen saturation, and comorbidities help predict hospitalization requirements, several biochemical markers may help evaluate disease severity [8], 9]. Several studies have demonstrated that markers such as interleukin-8, high-sensitivity troponin I (hs-TnI), soluble suppression of tumorigenicity 2, troponins, natriuretic peptides, and neutrophil-lymphocyte ratio (NLR) can predict disease severity, prognosis, and long-term cardiovascular risk in COVID-19 patients [10], [11], [12], [13]. Copeptin has been linked to impaired cardiovascular outcomes in patients with heart failure, acute myocardial infarction, and stable chronic heart failure [6]. Several recent studies have also indicated that copeptin is an effective biomarker for differentiating COVID-19-associated pneumonia from community-acquired pneumonia and for predicting disease severity and 28-day mortality [14].

Patients with severe COVID-19 with high mortality, extensive lung damage, and multiple organ failure are expected to experience more severe hemodynamic and osmotic disorders. These patients may release increased copeptin levels due to changes in blood pressure and plasma osmolality. Excessive cytokine and inflammatory responses in COVID-19 patients could contribute to increased copeptin levels, indicating the importance of studying its function in the disease [15]. Copeptin has demonstrated potential as a biomarker for disease severity, renal function decline, cardiovascular events, and neurological consequences in a variety of clinical diseases [16], [17], [18]. However, there is limited research on the predictive value of copeptin, including vascular events, in hospitalized COVID-19 patients. This study aimed to evaluate the effect of copeptin levels on the prediction of COVID-19-associated vascular events and mortality.

Materials and methods

One hundred seventy-two individuals who were diagnosed with COVID-19 at University of Health Sciences, Istanbul Bagcilar Training and Research Hospital, between January 2021 and October 2021, were included in this prospective observational study. Real-time reverse transcriptase polymerase chain reaction (CFX 96, Bio-Rad Laboratories, Inc., USA) from a nasal and/or throat swab that was SARS-CoV-2 positive was used to diagnose COVID-19. Only patients above 18 years of age were enrolled and treated according to the Ministry of Health’s COVID-19 recommendations. The Institutional Research Ethics Committee approved the study (date: 06/11/2020, number: 2020.11.1.05.173. r2.179), and signed informed consent was obtained. Clinical data including demographic and clinical details were collected. At the time of admission, the patient’s radiological and laboratory findings were documented. Medical procedures, time between hospital admission and ICU transfer, need for ICU care while the patient was in the hospital, and overall length of hospital stay were noted.

Blood samples for serum copeptin measurements were collected in serum separator tubes (SST, BD Vacutainer, SST™ II Advance, 13 × 100 mm, 5.0 mL). Blood samples were centrifuged at 2,000 × g for 10 min after coagulation, serum was extracted, and the samples were stored at −80 °C in the biochemistry laboratory. Hemolysis indices of serum samples were evaluated and samples with hemolysis were excluded from the study. Biochemical and immunoassay tests were conducted using a Cobas 8,000 (Roche Diagnostic, Mannheim, Germany). Complete blood count analysis was performed using a Mindray BC-6800Plus (BC-6800P, Mindray, Shenzhen, China).

Copeptin levels in the samples were measured using an enzyme-linked immunosorbent assay (ELISA) kit (catalog number: E-EL-H0851; Elabscience Biotechnology Co., Ltd., Houston, Texas, USA) on an ELX800DA ELISA analyzer (Diagnostic Automation Inc., Calabasas, CA, USA). The absorbance of copeptin was measured spectrophotometrically at 450 nm. The analytical sensitivity of copeptin was 18.75 pg/mL, with an analytical measurement range of 31.25–2,000 pg/mL. The samples were studied at a 1/5 dilution, which resulted in copeptin concentrations in ng/mL rather than pg/mL. The coefficient of variation for within-run and between-day precision for copeptin has been reported to be less than 10 %.

Under earlier research and recommendations, the terms chronic kidney disease (CKD), deep vein thrombosis (DVT), chronic obstructive pulmonary disease (COPD), and cerebral vascular accident (CVA) are defined. The presence of acute myocardial injury, as shown by aberrant cardiac markers in the presence of signs of acute myocardial ischemia, is the clinical definition of myocardial infarction (MI) [19]. A diagnosis of peripheral artery disease (PAD), coronary artery disease, percutaneous coronary intervention, or prior MI or bypass surgery was suggestive of vascular disease.

Results

One hundred seventy-two patients (93 male and 79 female) were enrolled, and the average age was 56.6 ± 15.6 years. During the hospitalization period of these 172 patients, 24 patients had major ischemic events, 45 were transferred to the ICU, 43 needed advanced ventilator support, and 33 died. Detailed clinical, demographic, and laboratory data of all included patients are presented in Table S1.

Depending on the patient’s in-hospital mortality, we classified the patients into two groups: 33 patients in the non-survivor group and 139 patients in the survivor group. Mean age (64.4 ± 15.0 years vs. 54.8 ± 15.2 years; p=0.001), MI rate (12.1 % vs. 0.71 %; p=0.005), major ischemic event rate (27.3 % vs. 10.8 %; p=0.023), ICU admission rate (75.8 % vs. 14.4 %; p<0.001), and advanced ventilatory support rate (72.7 % vs. 13.7 %; p<0.001) were significantly higher in the non-survivor group compared with the survivor group. Regarding biochemical variables, copeptin (3.52 [1.66–6.41] vs. 1.97 [0.98–4.17]; p=0.018), pro-brain natriuretic peptide (pro-BNP) (1,622 [256–5,846] vs. 70 [70–78]; p<0.001), interleukin-6 (IL-6) (1,214 [78–5,000] vs. 6 [6–9]; p<0.001), procalcitonin (2.14 [0.57–14.1] vs. 0.05 [0.03–0.19]; p<0.001), fibrinogen (542 [482–624] vs. 454 [408–557]; p<0.001), D-dimer (0.71 [0.32–1.62] vs. 0.19 [0.12–0.43]; p<0.001), C-reactive protein (CRP) (80.6 [18.0–146] vs. 21.1 [7.82–50.4]; p<0.001), troponin-T (24.2 [7.50–40.0] vs. 4.00 [2.40–6.40]; p<0.001), neutrophil counts (7.38 [4.64–9.78] vs. 3.78 [2.71–5.71]; p<0.001), and NLR (9.98 [3.90–16.8] vs. 2.21 [1.62–3.46]; p<0.001) were significantly higher and lymphocyte count (0.53 [0.32–0.72] vs. 0.97 [0.68–1.39]; p<0.001) was significantly lower in the non-survivor group. Detailed comparisons of the demographic, clinical, and laboratory data of the survivor and non-survivor groups are presented in Table 1.

We stratified the groups according to major ischemic events: 24 patients formed the major ischemic event-positive (+) group and 148 patients formed the major ischemic event-negative (−) group. The mean age (64.4 ± 15.2 vs. 55.4 ± 15.3; p=0.008), ICU admission rate (100 % vs. 14.2 %; p<0.001), and advanced ventilatory support rate (100 % vs. 12.8 %; p<0.001) were significantly higher in the major ischemic event (+) group. Regarding laboratory parameters, copeptin (5.26 [2.50–6.60] vs. 1.87 [0.99–4.02]; p<0.001), pro-BNP (377 [77–3,300] vs. 70 [70–132]; p<0.001), IL-6 (53 [8–1,326] vs. 6 [6–28]; p=0.002), procalcitonin (0.17 [0.06–2.62] vs. 0.06 [0.03–0.42]; p=0.015), and troponin-T (7.25 [4.60–18.1] vs. 4.10 [2.40–8.10]; p=0.012) levels were significantly higher in the ischemic event (+) group. Detailed comparisons of the demographic, clinical, and laboratory data of the ischemic event (+) and (−) groups are presented in Table 2.

Although we investigated the association between copeptin levels and several laboratory parameters, we did not find any statistically significant correlations. In our study population, we used regression analysis to identify the independent risk factors for major ischemic events and in-hospital mortality. Copeptin levels alone were a risk factor for both major ischemic events (OR=1.403; 95 % CI: 1.170–1.682; p<0.001) and in-hospital mortality (OR=1.241; 95 % CI: 1.060–1.454; p=0.007), as determined by univariate logistic regression analysis. Multivariate logistic regression analysis revealed that copeptin levels (OR=1.391; 95 % CI: 1.126–1.718; p=0.002) were independently associated with major ischemic events after adjusting for age, sex, smoking, diabetes mellitus, hypertension, COPD, CKD, pro-BNP, and hemoglobin. Multivariate logistic regression analysis revealed that copeptin levels (OR=1.368; 95 % CI: 1.078–1.740; p=0.010) were independently associated with in-hospital mortality after adjusting for age, sex, smoking, diabetes mellitus, hypertension, COPD, CKD, pro-BNP, hemoglobin, albumin, IL-6, D-dimer, urea, and Troponin T levels. A cut-off value of 5.161 for copeptin level was related to 54.2 % sensitivity and 85.1 % specificity (AUC: 0.727; 95 % CI: 0.654–0.792; p<0.001) for predicting major ischemic events, and a cut-off value of 3.304 for copeptin level was related to 51.5 % sensitivity and 71.9 % specificity (AUC: 0.633; 95 % CI: 0.556–0.705; p=0.018) for predicting in-hospital mortality (Figure 1A and B).

Figure 1:

Receiver operating characteristic curve analyses demonstrating the diagnostic performance of copeptin levels. (A) ROC curve analysis of copeptin levels for diagnosing major ischemic events. (B) ROC curve analysis of copeptin levels for diagnosing in-hospital mortality.

There was no significant difference in copeptin levels between the groups classified according to age, sex, comorbidities (diabetes mellitus, hypertension, and coronary artery disease), or smoking status (p>0.05). Copeptin levels were significantly higher in patients admitted to the ICU than in those who were not admitted (3.21 [1.41–6.06] vs. 1.89 [0.98–3.98]; p=0.014). Patients requiring advanced ventilatory support had significantly higher copeptin levels than those who did not (3.21 [1.35–6.29] vs. 1.89 [0.99–4.02]; p=0.019), as shown in Table 3.

Discussion

We evaluated the predictive value of copeptin, including major vascular events (CVA, venous thromboembolism, and MI) in hospitalized COVID-19 patients. Copeptin levels were significantly higher among individuals who did not survive, experienced vascular events, were admitted to the ICU, or required advanced respiratory support. Furthermore, according to regression analysis, copeptin level was an independent risk factor for both major ischemic events and in-hospital mortality.

COVID-19 is an epidemic disease with multiple clinical manifestations, and the respiratory system is its main target [20]. The severity of the disease varies greatly, ranging from infection with no symptoms to a severe condition that requires immediate medical attention [21]. Biomarkers provide significant prognostic knowledge that could help in the decision-making process, and the identification of individuals at risk for fatal outcomes could promote better monitoring and early augmentation of treatment. In hospitalized COVID-19 patients, a correlation between inflammatory and coagulation indicators and organ failure and death has been observed [22], 23]. In COVID-19, some biomarkers have become effective prognostic indicators, especially hs-Tn, galectin-3, and N-terminal pro-B-type natriuretic peptide (NT-proBNP) [24]. The results of our study were consistent with those of previous studies; pro-BNP, D-dimer, CRP, IL-6, troponin levels, NLR, procalcitonin, and fibrinogen were significantly higher in the non-survivor group than in the survivor group [25], [26], [27], [28].

As the two molecules are co-released in an equimolar ratio, copeptin, the C-terminal section of the arginine vasopressin precursor peptide, is more easily quantified than vasopressin [4], 5]. Numerous cell types, especially vascular endothelial cells, release copeptin in response to several stimuli such as endothelium damage, hypoxia, and inflammatory cytokines [5]. Infectious disorders, cardiovascular conditions, renal failure, and cerebrovascular diseases are the only few clinical conditions for which copeptin has been documented to have predictive significance in the general population [5].

Only a few investigations have shown an association between serum copeptin levels and severity of COVID-19 [29]. Kaufmann et al. observed increased copeptin in hospitalized COVID-19 patients, having median values higher than the normal range for a healthy population [30]. Gregoriano et al. reported that copeptin accurately predicted 30-day all-cause mortality in COVID-19 patients [31]. Rita et al. verified these findings in a larger cohort and demonstrated that copeptin levels were related to hospital stay duration and a consistently more complicated medical course, as composite results were able to predict sepsis and acute renal damage [32]. Upon admission, serum copeptin levels were remarkably elevated in individuals diagnosed with severe COVID-19, distinct from those with mild to moderate presentations of the disease [33], [34], [35]. Another study demonstrated the efficacy of copeptin in distinguishing COVID-19 pneumonia from community-acquired pneumonia (CAP), indicating higher serum copeptin levels in patients with COVID-19 than in patients with CAP [15]. Alongside presepsin and soluble ST2, novel biomarkers such as copeptin are increasingly recognized as markers of cardiovascular injury in COVID-19 and may be associated with poor prognosis [36]. Patients who developed septic shock during their ICU stay exhibited a significant increase in copeptin levels, whereas none of the biochemical parameters assessed predicted the occurrence of septic shock. Specifically, early copeptin levels greater than 23.4 pmol/L were associated with a significantly higher risk of requiring renal replacement therapy during hospitalization [37]. In a recently published study, contrary to our findings, no significant difference was found between the ICU group and the non-ICU or control groups. This situation has been linked to the use of glucocorticoids in ICU patients. Accordingly, under hyperinflammatory conditions, the prognostic utility of copeptin in COVID-19 may be limited due to corticosteroid administration [38]. Our findings indicated that COVID-19 patients in the ischemic event (+) group had significantly higher copeptin levels than COVID-19 patients in the ischemic event (−) group. Regression analysis revealed that the copeptin level was an independent risk factor for both major ischemic events and in-hospital mortality.

Our study has some limitations. First, the sample size of COVID-19 patients was relatively small, and the study had a single-center design. Secondly, only a single measurement was obtained from the patients; however, the prognostic value of copeptin could be better elucidated through serial measurements. We could not classify patients according to their medication 

Conclusion

COVID-19 infection is associated with severe respiratory complications. However, fatal cardiovascular complications have also been reported. The main findings of our study were the predictive performance (in-hospital mortality, need for advanced ventilator support, and ICU admission) of copeptin, including vascular events (CVA, venous thromboembolism, and MI), in hospitalized COVID-19 patients. Copeptin assessment at admission for early risk stratification in patients hospitalized with COVID-19 can help predict mortality and major ischemic events. However, more extensive studies are required to determine the critical importance of copeptin.