Copeptin in the differential diagnosis of hyponatremia

Copeptin as a diagnostic and prognostic biomarker in pediatric diseases

Arginine vasopressin (AVP) plays a main role in maintaining the homeostasis of fluid balance and vascular tone and in regulating the endocrine stress response in response to osmotic, hemodynamic and stress stimuli. However, the difficulty in measuring AVP limits its clinical application. Copeptin, the C-terminal part of the AVP precursor, is released in an equimolar concentration mode with AVP from the pituitary but is more stable and simple to measure. Therefore, copeptin has emerged as a promising surrogate marker of AVP with excellent potential for the diagnosis, differentiation and prognosis of various diseases in recent decades. However, its application requires further validation, especially in the pediatric population. This review focuses on the clinical value of copeptin in different pediatric diseases and the prospects for its application as a potential biomarker.

Copeptin as a surrogate marker for arginine vasopressin: analytical insights, current utility, and emerging applications

Copeptin is a 39-amino-acid long glycosylated peptide with a leucine-rich core segment in the C-terminal part of pre-pro-vasopressin. It exhibits a rapid response comparable to arginine vasopressin (AVP) in response to osmotic, hemodynamic, and nonspecific stress-related stimuli. This similarity can be attributed to equimolar production of copeptin alongside AVP. However, there are markedly different decay kinetics for both peptides, with an estimated initial half-life of copeptin being approximately two times longer than that of AVP. Like AVP, copeptin correlates strongly over a wide osmolality range in healthy individuals, making it a useful alternative to AVP measurement. While copeptin does not appear to be significantly affected by food intake, small amounts of oral fluid intake may result in a significant decrease in copeptin levels. Compared to AVP, copeptin is considerably more stable in vitro. An automated immunofluorescent assay is now available and has been used in recent landmark trials. However, separate validation studies are required before copeptin thresholds from these studies are applied to other assays. The biological variation of copeptin in presumably healthy subjects has been recently reported, which could assist in defining analytical performance specifications for this measurand. An established diagnostic utility of copeptin is in the investigation of polyuria-polydipsia syndrome and copeptin-based testing protocols have been explored in recent years. A single baseline plasma copeptin >21.4 pmol/L differentiates AVP resistance (formerly known as nephrogenic diabetes insipidus) from other causes with 100% sensitivity and specificity, rendering water deprivation testing unnecessary in such cases. In a recent study among adult patients with polyuria-polydipsia syndrome, AVP deficiency (formerly known as central diabetes insipidus) was more accurately diagnosed with hypertonic saline-stimulated copeptin than with arginine-stimulated copeptin. Glucagon-stimulated copeptin has been proposed as a potentially safe and precise test in the investigation of polyuria-polydipsia syndrome. Furthermore, copeptin could reliably identify those with AVP deficiency among patients with severe hypernatremia, though its diagnostic utility is reportedly limited in the differential diagnosis of profound hyponatremia. Copeptin measurement may be a useful tool for early goal-directed management of post-operative AVP deficiency. Additionally, the potential prognostic utility of copeptin has been explored in other diseases. There is an interest in examining the role of the AVP system (with copeptin as a marker) in the pathogenesis of insulin resistance and diabetes mellitus. Copeptin has been found to be independently associated with an increased risk of incident stroke and cardiovascular disease mortality in men with diabetes mellitus. Increased levels of copeptin have been reported to be independently predictive of a decline in estimated glomerular filtration rate and a greater risk of new-onset chronic kidney disease. Furthermore, copeptin is associated with disease severity in patients with autosomal dominant polycystic kidney disease. Copeptin predicts the development of coronary artery disease and cardiovascular mortality in the older population. Moreover, the predictive value of copeptin was found to be comparable with that of N-terminal pro-brain natriuretic peptide for all-cause mortality in patients with heart failure. Whether the measurement of copeptin in these conditions alters clinical management remains to be demonstrated in future studies.

Impact Factors of Blood Copeptin Levels in Health and Disease States

OBJECTIVE

Copeptin, the C-terminal glycopeptide of provasopressin, is released into the circulation in an equimolar manner with arginine vasopressin (AVP) when fluid homeostasis changes or has somatic stress. Copeptin is considered a potential alternative to AVP due to its advantages in facilitating assays. Although there have been several studies and reviews that have focused on the marker potential of copeptin in diseases involving changes in AVP, studies on its characteristics and factors that may influence its secretion have not been reviewed before.

METHODS

We summarize the influencing factors associated with copeptin levels in healthy and disease states, show the changes in copeptin levels under different physiologic and pathophysiologic conditions, calculate the changes in copeptin levels under different physiologic and pathophysiologic conditions, and compare them according to the type of stimuli. We also report research advances in copeptin changes in the diagnosis and prognosis of endocrine-related diseases.

RESULTS

Males have higher copeptin levels. Decreased copeptin levels are mainly caused by reduced blood volume and some diseases (eg, obesity). Under normal physiologic conditions, the effects of stress, endocrine axis stimulation, and blood volume increase on copeptin levels gradually increase. Under severe disease conditions (eg, sepsis), copeptin would remain at consistently high levels under compound stimuli and these elevated levels are associated with a poor prognosis of the disease.

CONCLUSION

Summarizing the influencing factors of copeptin can help us better understand the biologic features of copeptin and the similarities and differences between AVP and copeptin.

Long-term Outcome of a Chihuahua With Idiopathic Syndrome of Inappropriate Antidiuretic Hormone Secretion

An approximately 3 yr old female Chihuahua was presented for evaluation of polyuria and polydipsia noted by the owner after adoption. Serum biochemistry and urinalysis revealed hyponatremia, hypochloremia, hypo-osmolality, and normal fractional excretion of sodium. Serum antidiuretic hormone concentration was 5.54 pg/mL and serum copeptin concentration was 135.40 pg/mL. The antidiuretic hormone value was above the reported range for healthy dogs and was considered inappropriate in light of serum osmolality. Idiopathic syndrome of inappropriate antidiuretic hormone secretion was considered the most likely diagnosis after excluding other potential causes, such as diuretic use, renal disease, adrenal disease, and thyroid dysfunction. The dog remains clinically well 2 yr after diagnosis without specific treatment other than minimal dietary salt supplementation. This case is unique because of the absence of systemic or neurologic signs, good long-term outcome without treatment, and use of novel diagnostic testing.

Novel Plasma Biomarkers Associated with Future Peripheral Atherosclerotic Disease and Abdominal Aortic Aneurysm-Insights from Contemporary Prospective Studies from the Malmö Diet and Cancer Study

INTRODUCTION

The potential utility of inflammatory and hemodynamic plasma biomarkers for the prediction of incident lower extremity arterial disease (LEAD), carotid artery stenosis (CAS), isolated atherosclerotic disease without concomitant abdominal aortic aneurysm (AAA), and isolated AAA without concomitant atherosclerotic disease has not yet been integrated in clinical practice. The main objective of this prospective study was to find predictive plasma biomarkers for cardiovascular disease and to evaluate differences in plasma biomarker profiles between asymptomatic and symptomatic CAS, as well as between isolated atherosclerotic disease and isolated AAA.

METHODS

Blood samples collected at baseline from participants in the prospective Malmö Diet and Cancer study (MDCS) cardiovascular cohort (n = 5550 middle-aged individuals; baseline 1991-1994) were used for plasma biomarker analysis. Validation of each incident cardiovascular diagnosis was performed by random sampling. Cox regression analysis was used to calculate hazard ratios (HRs) per one standard deviation increment of each respective log-transformed plasma biomarker with 95% confidence intervals (CI).

RESULTS

Adjusted lipoprotein-associated phospholipase A2 (Lp-PLA2) activity (HR 1.33; CI 1.17-1.52) and mass (HR 1.20; CI 1.05-1.37), C-reactive protein (CRP) (HR 1.55; CI 1.36-1.76), copeptin (HR 1.46; CI 1.19-1.80), N-terminal pro-B-type natriuretic peptide (N-BNP) (HR 1.28; 1.11-1.48), and cystatin C (HR 1.19; 95% 1.10-1.29) were associated with incident symptomatic LEAD. Adjusted N-BNP (HR 1.59; CI 1.20-2.11), mid-regional proadrenomedullin (HR 1.40; CI 1.13-1.73), cystatin C (HR 1.21; CI 1.02-1.43), and CRP (HR 1.53; CI 1.13-1.73) were associated with incident symptomatic but not asymptomatic CAS. Adjusted HR was higher for Lp-PLA2 (mass) for incident isolated AAA compared to for isolated atherosclerotic disease.

CONCLUSIONS

Plasma biomarker profile data support that subclinical vascular inflammation and cardiovascular stress seem to be relevant for the development of atherosclerotic disease and AAA.

Hyponatremia in the emergency department: an overview of diagnostic and therapeutic approach

INTRODUCTION

Hyponatremia, defined as a serum sodium concentration <135 mmol/l, is a frequent electrolyte disorder in patients presenting to an emergency department (ED). In this context, appropriate diagnostic and therapeutic management is rarely performed and challenging due to complex pathophysiologic mechanisms and a variety of underlying diseases.

OBJECTIVE

To implement a feasible pathway of central diagnostic and therapeutic steps in the setting of an ED.

METHODS

We conducted a narrative review of the literature, considering current practice guidelines on diagnosis and treatment of hyponatremia. Underlying pathophysiologic mechanisms and management of adverse treatment effects are outlined. We also report four cases observed in our ED.

RESULTS

Symptoms associated with hyponatremia may appear unspecific and range from mild cognitive deficits to seizures and coma. The severity of hyponatremia-induced neurological manifestation and the risk of poor outcome is mainly driven by the rapidity of serum sodium decrease. Therefore, emergency treatment of hyponatremia should be guided by symptom severity and the assumed onset of hyponatremia development, distinguishing acute (<48 hours) versus chronic hyponatremia (>48 hours).

CONCLUSIONS

Especially in moderately or severely symptomatic patients presenting to an ED, the application of a standard management approach appears to be critical to improve overall outcome. Furthermore, an adequate work-up in the ED enables further diagnostic and therapeutic evaluation during hospitalization.

Chronic Hyponatremia: The Role of Reset Osmostat in Patients with Suspected SIAD

Background: Hyponatremia is common, particularly among the elderly. Reset osmostat (RO) serves as an alternative diagnosis to the syndrome of inappropriate antidiuresis (SIAD). There is limited information available regarding the prevalence of RO in outpatient clinics and hospital wards. The water-diluting test is considered the gold standard for the diagnosis of RO. The recent identification of copeptin provides an additional diagnostic marker alongside the utilization of fractional uric acid excretion. Methods: This single-center, prospective, observational study involved eight patients undergoing a water-diluting test over a study period of 2 years. Results: Reset osmostat was diagnosed in 50% of cases, while SIAD was confirmed in one patient. The tests were inconclusive for the remaining three patients. Conclusions: Our findings suggest that reset osmostat, despite its rarity, is a plausible diagnosis in chronic hyponatremia. The relevance of copeptin could not be confirmed in this study. Moreover, fractional uric acid excretion might be as effective as the water-diluting test in diagnosing reset osmostat.

Updates in hyponatremia and hypernatremia

PURPOSE OF REVIEW

Hyponatremia and hypernatremia are commonly encountered electrolyte abnormalities that require timely and careful intervention, as they can be associated with significant morbidity and mortality.

RECENT FINDINGS

This review article addresses the etiology, presentation, diagnosis, and management of both hyponatremia and hypernatremia, emphasizing the latest advancements and emerging trends in pediatric care.

SUMMARY

A methodical approach is needed to accurately assess and treat hyponatremia and hypernatremia. Both conditions continue to rely on serum and urine testing, however newer tests such as copeptin and stimulated testing may hold promise to further refine testing in the future.

Preoperative Serum Copeptin Can Predict Delayed Hyponatremia after Pituitary Surgery in the Absence of Arginine Vasopressin Deficiency

BACKGRUOUND

Delayed postoperative hyponatremia (DPH) is the most common cause of readmission after pituitary surgery. In this study, we aimed to evaluate the cutoff values of serum copeptin and determine the optimal timing for copeptin measurement for the prediction of the occurrence of DPH in patients who undergo endoscopic transsphenoidal approach (eTSA) surgery and tumor resection.

METHODS

This was a prospective observational study of 73 patients who underwent eTSA surgery for pituitary or stalk lesions. Copeptin levels were measured before surgery, 1 hour after extubation, and on postoperative days 1, 2, 7, and 90.

RESULTS

Among 73 patients, 23 patients (31.5%) developed DPH. The baseline ratio of copeptin to serum sodium level showed the highest predictive performance (area under the curve [AUROC], 0.699), and its optimal cutoff to maximize Youden's index was 2.5×10-11, with a sensitivity of 91.3% and negative predictive value of 92.0%. No significant predictors were identified for patients with transient arginine vasopressin (AVP) deficiency. However, for patients without transient AVP deficiency, the copeptin-to-urine osmolarity ratio at baseline demonstrated the highest predictive performance (AUROC, 0.725). An optimal cutoff of 6.5×10-12 maximized Youden's index, with a sensitivity of 92.9% and a negative predictive value of 94.1%.

CONCLUSION

The occurrence of DPH can be predicted using baseline copeptin and its ratio with serum sodium or urine osmolarity only in patients without transient AVP deficiency after pituitary surgery.

Mechanisms of hyponatremia and diabetes insipidus after acute spinal cord injury: a critical review

The incidence of hyponatremia after spinal cord injury was reported to be between 25 and 80%. Hyponatremia can lead to a variety of clinical symptoms, from mild to severe and even life-threatening. Hyponatremia is often associated with diabetes insipidus, which refers to insufficient arginine vasopressin (AVP) secretion or defective renal response to AVP, with clinical manifestations of syndromes such as hypoosmolality, polydipsia, and polydipsia. Recent mechanistic studies on hyponatremia and diabetes insipidus after acute spinal cord injury have been performed in isolation, without integrating the above two symptoms into different pathological manifestations that occur in the same injury state and without considering the acute spinal cord injury patient's condition as a whole. The therapeutic principles of CSWS and SIADH are in opposition to one another. It is not easy to identify the mechanism of hyponatremia in clinical practice, which makes selecting the treatment difficult. According to the existing theories, treatments for hyponatremia and diabetes insipidus together are contraindicated, whether the mechanism of hyponatremia is thought to be CSWS or SIADH. In this paper, we review the mechanism of these two pathological manifestations and suggest that our current understanding of the mechanisms of hyponatremia and diabetes insipidus after high acute cervical SCI is insufficient, and it is likely that there are other undetected pathogenetic mechanisms.

Predicting autosomal dominant polycystic kidney disease progression: review of promising Serum and urine biomarkers

Autosomal dominant polycystic kidney disease (ADPKD) is one of the leading causes of end-stage renal disease. In spite of the recent tremendous progress in the understanding of ADPKD pathogenesis, the molecular mechanisms of the disease remain incompletely understood. Considering emerging new targeted therapies for ADPKD, it has become crucial to disclose easily measurable and widely available biomarkers for identifying patients with future rapid disease progression. This review encompasses all the research with a shared goal of identifying promising serum or urine biomarkers for predicting ADPKD progression or response to therapy. The rate of the ADPKD progress varies significantly between patients. The phenotypic variability is only partly explained by the underlying genetic lesion diversity. Considering significant decline in kidney function in ADPKD is not usually evident until at least 50% of the parenchyma has been destroyed, conventional kidney function measures, such as glomerular filtration rate (GFR), are not suitable for monitoring disease progression in ADPKD, particularly in its early stages. Since polycystic kidney enlargement usually precedes the decline in GFR, height-adjusted total kidney volume (ht-TKV) has been accepted as an early biomarker for assessing disease severity in ADPKD patients. However, since measuring ht-TKV is time-consuming and observer-dependent, the identification of a sensitive and quickly measurable biomarker is of a great interest for everyday clinical practice. Throughout the last decade, due to development of proteomic and metabolomic techniques and the enlightenment of multiple molecular pathways involved in the ADPKD pathogenesis, a number of urine and serum protein biomarkers have been investigated in ADPKD patients, some of which seem worth of further exploring. These include copeptin, angiotensinogen, monocyte chemoattractant protein 1, kidney injury molecule-1 and urine-to-plasma urea ratio among many others. The aim of the current review is to provide an overview of all of the published evidence on potentially clinically valuable serum and urine biomarkers that could be used for predicting disease progression or response to therapy in patients with ADPKD. Hopefully, this review will encourage future longitudinal prospective clinical studies evaluating proposed biomarkers as prognostic tools to improve management and outcome of ADPKD patients in everyday clinical practice.

Syndrome of Inappropriate Antidiuresis: From Pathophysiology to Management

Hyponatremia is the most common electrolyte disorder, affecting more than 15% of patients in the hospital. Syndrome of inappropriate antidiuresis (SIAD) is the most frequent cause of hypotonic hyponatremia, mediated by nonosmotic release of arginine vasopressin (AVP, previously known as antidiuretic hormone), which acts on the renal V2 receptors to promote water retention. There are a variety of underlying causes of SIAD, including malignancy, pulmonary pathology, and central nervous system pathology. In clinical practice, the etiology of hyponatremia is frequently multifactorial and the management approach may need to evolve during treatment of a single episode. It is therefore important to regularly reassess clinical status and biochemistry, while remaining alert to potential underlying etiological factors that may become more apparent during the course of treatment. In the absence of severe symptoms requiring urgent intervention, fluid restriction (FR) is widely endorsed as the first-line treatment for SIAD in current guidelines, but there is considerable controversy regarding second-line therapy in instances where FR is unsuccessful, which occurs in around half of cases. We review the epidemiology, pathophysiology, and differential diagnosis of SIAD, and summarize recent evidence for therapeutic options beyond FR, with a focus on tolvaptan, urea, and sodium-glucose cotransporter 2 inhibitors.

Copeptin levels in hospitalized infants and children with suspected vasopressin-dependent disorders: a case series

OBJECTIVES

There have been recent advances assessing copeptin levels in adults with suspected disorders of vasopressin release. Very limited data exits on copeptin levels in children and infants, especially in a critically-ill hospitalized population where hyper- and hypo-natremia are very common. Our objective is to describe the institutional experience assessing copeptin levels in hospitalized infants and children with hyper- or hypo-natremia.

METHODS

We performed a single-center retrospective case series of all infants, children, and adolescents who had an ultrasensitive plasma copeptin level obtained between 2019-2021.

RESULTS

A total of 29 critically ill patients (6 infants) were identified with 38 % of patients having copeptin levels after neurosurgical procedures for tumors or trauma. Approximately 13/17 children with hypernatremia had CDI to diagnose CDI, A copeptin level ≤ 4.9 pmol/L resulted in an 88 % sensitivity (95 % CI 47-99 %), and 66 % specificity (95 % CI 30-93 %). Amongst those with hyponatremia levels were more variable, 8/12 children had SIAD with copeptin levels ranging 4.7-72.6 pmol/L.

CONCLUSIONS

While difficult to conclude due to multiple limitations, this case series highlights that typical copeptin cutoffs used to diagnose DI in adults in an ambulatory setting may also translate to a critically-ill pediatric population. Large prospective studies are needed to confirm this observation. In addition, postoperative copeptin levels could potentially be utilized as an additional marker to predict permanent from transient DI, but much larger studies are needed. Further work is needed to establish normative copeptin levels in infants and patients with SIAD.

Severe hyponatraemia with cerebral oedema after Pfizer BNT162b2 mRNA vaccination against COVID-19

Background

Severe hyponatraemia can lead to serious neurological complications including coma, seizure and death. Hyponatraemia and the Syndrome of Inappropriate Antidiuretic Hormone (SIADH) has been previously described in cases of COVID-19, however there have been few reports post vaccination. We describe a case of severe hyponatraemia post second Pfizer BNT162b2 mRNA vaccination against COVID-19.

Case presentation

A 48-year-old previously well woman presented to the emergency department with severe headaches and confusion one day after she received her second Pfizer COVID-19 vaccination. She reported no more than 2.5 L fluid intake. Vital signs were normal. Laboratory investigation revealed serum sodium 113 mmol/L, potassium 3.4 mmol/L, urea 3.5 mmol/L and serum osmolality 266 mmol/kg. TSH, random cortisol and C-reactive protein levels were normal. She was found to be in urinary retention and developed marked polyuria post in dwelling catheter insertion. Following this she underwent spontaneous and rapid correction of serum sodium without intervention. Retrospective analysis showed an inappropriately high copeptin of 4.4 pmol/L.

Conclusions

It is important to be cautioned and aware of hyponatraemia as an immediate side effect of COVID-19 vaccination. The exact mechanism is unknown and further research is required to understand the acute endocrine effects which may arise in response to COVID-19 vaccination.

Serum copeptin levels at day two after pituitary surgery and ratio to baseline predict postoperative central diabetes insipidus

PURPOSE

Central diabetes insipidus is a complication that may occur after pituitary surgery and has been difficult to predict. This study aimed to identify the cutoff levels of serum copeptin and its optimal timing for predicting the occurrence of central diabetes insipidus in patients who underwent transsphenoidal surgery.

METHODS

This was a prospective observational study of patients who underwent transsphenoidal surgery for pituitary gland or stalk lesions. Copeptin levels were measured before surgery, 1 h after extubation, and on postoperative days 1, 2, 7, and 90.

RESULTS

Among 73 patients, 14 (19.2%) and 13 (17.8%) patients developed transient and permanent central diabetes insipidus, respectively. There was no significant difference in copeptin levels before surgery and 1 h after extubation; copeptin levels on postoperative days 1, 2, 7, and 90 were significantly lower in patients with permanent central diabetes insipidus than in those without central diabetes insipidus. Copeptin measurement on postoperative day 2 exhibited the highest performance for predicting permanent central diabetes insipidus among postoperative days 1, 2, and 7 (area under the curve [95% confidence interval] = 0.754 [0.632-0.876]). Serum copeptin level at postoperative day 2(< 3.1 pmol/L) showed a sensitivity of 92.3% and a negative predictive value of 97.1%. The ratio of copeptin at postoperative day 2 to baseline (< 0.94) presented a sensitivity of 84.6% and a negative predictive value of 94.9%. The copeptin levels > 3.4 and 7.5 pmol/L at postoperative day 2 and 7 may have ruled out the occurrence of CDI with a negative predictive value of 100%.

CONCLUSION

The copeptin level at postoperative day 2 and its ratio to baseline can predict the occurrence of permanent central diabetes insipidus after pituitary surgery.

Korean Society of Nephrology 2022 recommendations on controversial issues in diagnosis and management of hyponatremia

The Korean Society for Electrolyte and Blood Pressure Research, in collaboration with the Korean Society of Nephrology, has published a clinical practice guideline (CPG) document for hyponatremia treatment. The document is based on an extensive evidence-based review of the diagnosis, evaluation, and treatment of hyponatremia with the multidisciplinary participation of representative experts in hyponatremia with methodologist support for guideline development. This CPG consists of 12 recommendations (two for diagnosis, eight for treatment, and two for special situations) based on eight detailed topics and nine key questions. Each recommendation begins with statements graded by the strength of the recommendations and the quality of the evidence. Each statement is followed by rationale supporting the recommendations. The committee issued conditional recommendations in favor of rapid intermittent bolus administration of hypertonic saline in severe hyponatremia, the use of vasopressin receptor antagonists in heart failure with hypervolemic hyponatremia, and syndrome of inappropriate antidiuresis with moderate to severe hyponatremia, the individualization of desmopressin use, and strong recommendation on the administration of isotonic fluids as maintenance fluid therapy in hospitalized pediatric patients. We hope that this CPG will provide useful recommendations in practice, with the aim of providing clinical support for shared decision-making to improve patient outcomes.

Copeptin as a Diagnostic and Prognostic Biomarker in Cardiovascular Diseases

Copeptin is the carboxyl-terminus of the arginine vasopressin (AVP) precursor peptide. The main physiological functions of AVP are fluid and osmotic balance, cardiovascular homeostasis, and regulation of endocrine stress response. Copeptin, which is released in an equimolar mode with AVP from the neurohypophysis, has emerged as a stable and simple-to-measure surrogate marker of AVP and has displayed enormous potential in clinical practice. Cardiovascular disease (CVD) is currently recognized as a primary threat to the health of the population worldwide, and thus, rapid and effective approaches to identify individuals that are at high risk of, or have already developed CVD are required. Copeptin is a diagnostic and prognostic biomarker in CVD, including the rapid rule-out of acute myocardial infarction (AMI), mortality prediction in heart failure (HF), and stroke. This review summarizes and discusses the value of copeptin in the diagnosis, discrimination, and prognosis of CVD (AMI, HF, and stroke), as well as the caveats and prospects for the application of this potential biomarker.

Approach to the Patient: Hyponatremia and the Syndrome of Inappropriate Antidiuresis (SIAD)

Hyponatremia is the most common electrolyte disturbance seen in clinical practice, affecting up to 30% of acute hospital admissions, and is associated with significant adverse clinical outcomes. Acute or severe symptomatic hyponatremia carries a high risk of neurological morbidity and mortality. In contrast, chronic hyponatremia is associated with significant morbidity including increased risk of falls, osteoporosis, fractures, gait instability, and cognitive decline; prolonged hospital admissions; and etiology-specific increase in mortality. In this Approach to the Patient, we review and compare the current recommendations, guidelines, and literature for diagnosis and treatment options for both acute and chronic hyponatremia, illustrated by 2 case studies. Particular focus is concentrated on the diagnosis and management of the syndrome of inappropriate antidiuresis. An understanding of the pathophysiology of hyponatremia, along with a synthesis of the duration of hyponatremia, biochemical severity, symptomatology, and blood volume status, forms the structure to guide the appropriate and timely management of hyponatremia. We present 2 illustrative cases that represent common presentations with hyponatremia and discuss the approach to management of these and other causes of hyponatremia.

Changes in Serum Creatinine Levels Can Help Distinguish Hypovolemic from Euvolemic Hyponatremia

Background and Objectives: Differentiating between hypovolemic (HH) and euvolemic hyponatremia (EH) is crucial for correct diagnosis and therapy, but can be a challenge. We aim to ascertain whether changes in serum creatinine (SC) can be helpful in distinguishing HH from EH. Materials and Methods: Retrospective analysis of patients followed in a monographic hyponatremia outpatient clinic of a tertiary hospital during 1 January 2014−30 November 2019. SC changes during HH and EH from eunatremia were studied. The diagnostic accuracy of the SC change from eunatremia to hyponatremia (∆SC) was analyzed. Results: A total of 122 hyponatremic patients, median age 79 years (70−85), 46.7% women. In total, 70/122 patients had EH, 52/122 HH. During hyponatremia, median SC levels increased in the HH group: +0.18 mg/dL [0.09−0.39, p < 0.001], but decreased in the EH group: −0.07 mg/dL (−0.15−0.02, p < 0.001), as compared to SC in eunatremia. HH subjects presented a higher rate of a positive ∆SC than EH (90.4% vs. 25.7%, p < 0.001). EH subjects presented a higher rate of a negative/null ∆SC than HH (74.3% vs. 9.6%, p < 0.001). ROC curve analysis found an AUC of 0.908 (95%CI: 0.853 to 0.962, p < 0.001) for ∆SC%. A ∆SC% ≥ 10% had an OR of 29.0 (95%CI: 10.3 to 81.7, p < 0.001) for HH. A ∆SC% ≤ 3% had an OR of 68.3 (95%CI: 13.0 to 262.2, p < 0.001) for EH. Conclusions: The assessment of SC changes from eunatremia to hyponatremia can be useful in distinguishing between HH and EH.

Approach to the Patient: "Utility of the Copeptin Assay"

Copeptin derives from the same precursor peptide preprovasopressin as arginine vasopressin (AVP). The secretion of both peptides is stimulated by similar physiological processes, such as osmotic stimulation, hypovolemia, or stress. AVP is difficult to measure due to complex preanalytical requirements and due to technical difficulties. In the last years, copeptin was found to be a stable, sensitive, and simple to measure surrogate marker of AVP release. Different immunoassays exist to measure copeptin. The 2 assays which have most often be used in clinical studies are the original sandwich immunoluminometric assay and its automated immunofluorescent successor. In addition, various enzyme-linked immunosorbent assay have been developed. With the availability of the copeptin assay, the differential diagnosis of diabetes insipidus was recently revisited. The goal for this article is therefore to first review the physiology of copeptin, and second to describe its use as marker for the differential diagnosis of vasopressin-dependent fluid disorders, mainly diabetes insipidus but also hyper- and hyponatremia. Furthermore, we highlight the role of copeptin as prognostic marker in other acute and chronic diseases.

Copeptin: Utility in Paediatric Patients with Hyponatraemia

INTRODUCTION

Copeptin concentrations are a useful component of the diagnostic workup of paediatric patients with polyuria and polydipsia, but the value of measuring copeptin in patients with hyponatraemia is less clear.

CASE REPORTS

We report 5 children with hyponatraemia in the context of different underlying pathologies. Copeptin concentrations were elevated in 4 cases (13.7, 14.4, 26.1, and 233 pmol/L; reference range 2.4-8.6 pmol/L), suggesting that non-osmoregulated vasopressin release (syndrome of inappropriate antidiuretic hormone) was the underlying mechanism for low sodium levels. In one of the patients, there was an underlying diagnosis of Schaaf-Yang syndrome (MAGEL2 gene mutation) with a clinical picture suggestive of dysregulated vasopressin production with inappropriately high and then low copeptin release. In one hyponatraemic patient, low copeptin concentrations indicated that non-osmoregulated arginine vasopressin release was not the cause of hyponatraemia and oliguria.

DISCUSSION

Copeptin measurement did not influence management acutely but helped to clarify the mechanism leading to hyponatraemia when the result was available. Relatively high and low copeptin concentrations in association with hypo- and hypernatraemia indicate dysregulated vasopressin production in Schaaf-Yang syndrome.

Circulating Biomarkers Predict Symptomatic but Not Asymptomatic Carotid Artery Stenosis

BACKGROUND

Subjects exposed to risk factors such as age, gender, hypertension, diabetes mellitus, and smoking are prone to atherosclerotic events.

AIMS

The main aim of this longitudinal cohort study was to determine whether the role of novel plasma biomarkers for atherosclerotic carotid artery disease is different in subjects developing symptomatic carotid artery stenosis (CAS), as opposed to those with incident asymptomatic CAS.

METHODS

The following biomarkers were measured in 5,550 middle-aged subjects in a population-based cohort study: C-reactive protein (CRP), lipoprotein-associated phospholipase A2 mass and activity, proneurotensin, midregional proadrenomedullin (MR-proADM), midregional proatrial natriuretic peptide (MR-proANP), N-terminal pro-B-type natriuretic peptide (NT pro-BNP), copeptin, and cystatin C. After exclusion of those with prevalent CAS, subjects were thereafter followed in national patient registers for 23.4 (interquartile range 19.5-24.3) years regarding incident symptomatic and asymptomatic CAS.

RESULTS

Among 110 patients with confirmed incident CAS, 56 were symptomatic and 54 were asymptomatic. When including conventional risk markers in a Cox regression analysis, NT pro-BNP (hazard ratio [HR] 1.59; 95% confidence interval [CI]: 1.20-2.11), MR-proADM (HR 1.40; CI: 1.13-1.73), cystatin C (HR 1.21; CI: 1.02-1.43), and CRP (HR 1.53; CI: 1.13-1.73) were independently associated with incident symptomatic CAS, whereas no plasma biomarker was associated with incident asymptomatic CAS.

CONCLUSION

Plasma biomarkers NT pro-BNP, MR-proADM, cystatin C, and CRP were independently associated with incident symptomatic CAS, whereas no such association could be demonstrated with incident asymptomatic CAS. As these biomarkers indicate future development of clinically relevant atherosclerotic CAS, their potential utility in relation to intensified preventive measures and selection of potential candidates for carotid surgery should be further evaluated.

Copeptin in fluid disorders and stress

Copeptin, a glycosylated peptide of 39 amino acids, is the C-terminal segment of arginine vasopressin (AVP) precursor peptide, which is consisted of two other fragments, vasopressin and neurophysin Ⅱ. The main physiological functions of AVP are fluid and osmotic balance, cardiovascular homeostasis and regulation of the endocrine stress response. Numerous studies have demonstrated that the endogenous AVP in plasma is a meaningful biomarker to guide diagnosis and therapy of diseases associated with fluids disorders and stress. However, due to its instability, short half-time life in circulation and lack of readily available AVP assays, clinical measurement of AVP is restricted. In contrast to AVP, copeptin which is released in an equimolar mode with AVP from the pituitary, has emerged as a stable and simple-to-measure surrogate marker of AVP and displays excellent potential in diagnosis, differentiation and prognosis of various diseases. This review will discuss the studies on the clinical value of copeptin in different diseases, especially in AVP-dependent fluids disorders, as well as issues and prospects of the application of this potential biomarker.

Prospective Comparison of Plasma Biomarker and Traditional Risk Factor Profiles for Incident Isolated Atherosclerotic Disease and Incident Isolated Abdominal Aortic Aneurysm

Background: Traditional risk factors for atherosclerotic disease (AD) are well-known, of which some are relevant also for abdominal aortic aneurysms (AAA). The present study compares the importance of plasma biomarkers and traditional risk factor profiles for incident AD without concomitant AAA (isolated AD) and AAA without concomitant AD (isolated AAA) during long-term follow-up.

Methods: In the Malmö Diet and Cancer Study—cardiovascular cohort, 5,381 participants were free from atrial fibrillation or flutter, AD (coronary artery disease, atherothrombotic ischemic stroke, carotid artery disease, or peripheral artery disease), and AAA underwent blood sampling under standardized fasting conditions between 1991 and 1994. Cox proportional hazards regression analysis was used to calculate hazard ratios (HR) with 95% CIs.

Results: During a median follow-up of 23.1 years, 1,152 participants developed isolated AD, and 44 developed isolated AAA. Adjusted HR for lipoprotein-associated phospholipase A2 (mass) (HR 1.53, 95% CI 1.14–2.04 vs. HR 1.05, 95% CI.99–1.12) was higher for incident isolated AAA compared to incident isolated AD, respectively. Mid-regional pro-adrenomedullin (MR-proADM) was associated with incident isolated AD (HR 1.17, 95% CI 1.1–1.25) and incident isolated AAA (HR 1.47, 95% CI 1.15–1.88). MR-proADM was correlated (r = 0.32; p < 0.001) to body mass index (BMI), and BMI was associated with increased risk of incident isolated AAA (HR 1.43, 95% CI 1.02–2). No participant with diabetes mellitus (DM) at baseline developed isolated AAA (0/44), whereas DM was associated with an increased risk of isolated AD (HR 2.57, 95% CI 2.08–3.18). Adjusted HR for male sex (HR 4.8, 95% CI 2.42–9.48, vs. HR 1.76, 95% CI 1.56–1.98) and current smoking (HR 4.79, 95% CI 2.42–9.47 vs. HR 1.97, 95% CI 1.73–2.23) were higher in the incident isolated AAA group compared to the incident isolated AD group, respectively.

Conclusions: The data supports the view that components of vascular inflammation and cardiovascular stress drives AAA development, whereas glycated cross-links in abdominal aortic wall tissue may have a plausible role in reducing AAA risk in individuals with DM.

Prevalence of adrenal insufficiency among patients with euvolemic hyponatremia

BACKGROUND

The diagnosis of syndrome of inappropriate anti-diuresis requires the exclusion of secondary adrenal insufficiency (AI) among patients with euvolemic hyponatremia (EuVHNa). Studies have suggested that about 2.7-3.8% of unselected patients presenting to the emergency room with EuVHNa have undiagnosed AI and it is as high as 15% among patients admitted to specialized units for evaluation of hyponatremia.

OBJECTIVE

To study the prevalence of AI among in-patients with EuVHNa in a general medical ward setting.

METHODS

This was a prospective, single-center observational study conducted among general medical in-patients with EuVHNa, defined as patients with a serum sodium <135 mmol/L, clinical euvolemia and urine spot sodium >30 mmol/L. Additionally, patients with recent vomiting, current renal failure, diuretic use and those with uncontrolled hyperglycemia were excluded. Adrenal functions were assessed by a modified adrenocorticotropic hormone (ACTH) stimulation test called the Acton Prolongatum™ stimulation test (APST). A cut-off cortisol value of <18 mg/dL after 60 min of ACTH injection was used to diagnose AI.

RESULTS

One hundred forty-one patients were included and underwent an APST. APST suggested 20/141 (14.2%) had undiagnosed AI. The commonest cause of AI (9/20) was secondary AI because of the use of steroids including inhaled steroids and indigenous medicines contaminated with steroids. In 5 (3.5%) patients hypopituitarism was newly diagnosed. Despite primary AI (PAI) not commonly presenting as EuVHNa, 2/20 patients had PAI.

CONCLUSIONS

AI is much commoner in our country, among in-patients with EuVHNa primarily driven by exogenous steroid use and undiagnosed hypopituitarism.

Role of copeptin in the diagnosis of traumatic neuroendocrine dysfunction

Traumatic neuroendocrine dysfunction may present with diabetes insipidus (DI) or with the syndrome of inappropriate antidiuretic hormone secretion (SIADH). Both these pathologies involve a disturbance in the antidiuretic hormone (ADH) secretion, causing dysnatremias. Diagnosis of posttraumatic ADH dysfunction is hampered by technical difficulties in ADH assessment, and relies mostly on non-specific serum sodium, serum and urine osmolality and diuresis, often leading to misdiagnosis in the acute care setting. Research now focuses on the diagnostic role of copeptin, a peptide secreted together with ADH in an equimolar fashion, and which can be accurately evaluated. Recent studies identified cut-off values of 2.6 pmol/L for baseline copeptin and of 4.9 and 3.8 pmol/L for hypertonic saline infusion and arginine infusion stimulated copeptin, respectively, for the diagnosis of DI in patients with polyuria-polydipsia syndrome. Although SIADH is more difficult to be explored due to its heterogeneity, a ratio of copeptin to urinary sodium below 30 pmol/mmol identifies euvolemic hyponatremia. Exploring the role of copeptin assessment in patients with traumatic brain injury (TBI) in the acute phase may improve their diagnosis accuracy, management and outcome.

Changes in copeptin levels before and 3 months after transsphenoidal surgery according to the presence of postoperative central diabetes insipidus

Copeptin levels reflect arginine vasopressin (AVP) release from the hypothalamus. Pituitary surgery often impairs AVP release and results in central diabetes insipidus (CDI). Here, we aimed to investigate how serum copeptin level changes 3 months after pituitary surgery and whether it has a diagnostic value for postoperative permanent CDI. Consecutive patients who underwent endoscopic transsphenoidal surgery at a single tertiary hospital were recruited. Serum copeptin levels were measured preoperatively and 3 months postoperatively. Among 88 patients, transient and permanent CDI occurred in 17 (19.3%) and 23 (26.1%), respectively. Three-month postoperative copeptin levels significantly declined from preoperative levels in permanent CDI group (P < 0.001, percentage difference =  - 42.2%) and also in the transient CDI group (P = 0.002, - 27.2%). Three months postoperative copeptin level < 1.9 pmol/L under normal serum sodium levels was the optimal cutoff value for diagnosing permanent CDI with an accuracy of 81.8%, while 3-month postoperative copeptin level ≥ 3.5 pmol/L excluded the CDI with a negative predictive value of 100%. Conclusively, 3 months postoperative copeptin levels significantly decreased from preoperative levels in the transient CDI group as well as the permanent CDI group. Three-month postoperative copeptin levels ≥ 3.5 pmol/L under normal serum sodium levels may be diagnostic for excluding postoperative CDI.

Use of Copeptin Levels to Predict the Resolution of Transient Postoperative SIADH

BACKGROUND

Copeptin levels reflect vasopressin activity and help classify osmoregulatory disorders. There is limited pediatric experience using copeptin to diagnose and manage diabetes insipidus, syndrome of inappropriate antidiuretic hormone secretion (SIADH), and bi- or tri-phasic postsurgical osmoregulatory disorders. In this report, we describe serial copeptin levels in an infant who developed transient SIADH after neurosurgery.

CASE DESCRIPTION

A 4-month-old infant with no prior pituitary dysfunction underwent endoscopic fenestration of a large arachnoid cyst (3.5 × 4.7 × 3.8 cm). He developed SIADH on postoperative day 4 with seizures, hyponatremia (sodium 121 mmol/L), and concentrated urine (535 mOsm/kg). His initial copeptin level was inappropriately high in the context of his hyponatremia. Copeptin levels decreased as his SIADH resolved. Serial copeptin levels correlated to the infant's increased ability to dilute urine.

CONCLUSION

Copeptin levels in this infant are consistent with levels described in adults and older children. Obtaining copeptin levels may improve providers' ability to quickly diagnose and manage SIADH amongst other heterogeneous causes of hyponatremia. Lastly, trending copeptin levels improved providers' ability to monitor SIADH progression, and may allow preemptive fluid titration for children with bi- or tri-phasic shifts in osmoregulation after neurological procedures.

Copeptin combined with National Early Warning Score for predicting survival in elderly critical ill patients at emergency department

OBJECTIVE

Copeptin, reflecting vasopressin release, as well as the National Early Warning Score (NEWS), reflecting the severity of critical illness, might qualify for survival prediction in elderly patients with critical illness. This prospective 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 combined 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 patients with critical illness at ED, comparing to either factor individually.

Distribution of plasma copeptin levels and influence of obesity in children and adolescents

In recent years, a more stable AVP surrogate, called copeptin, has been used as an adjuvant diagnostic tool for dysnatremia in adults and appears to be promising even in the pediatric age. The aim of this study is to present the distribution of plasma copeptin in a large pediatric cohort and to observe the influence of fluid consumption and obesity on its values. A cohort of 128 children and adolescents was divided into two groups on the basis of nocturnal deprivation (group A) or free access to oral fluids in the 6-8 h before blood collection (group B). At all distribution percentiles, copeptin levels were higher (p < 0.0001) in group A, as were plasma sodium levels and osmolality (p = 0.02 and p = 0.008, respectively). The influence of BMI on copeptin levels was investigated by dividing the cohort into nonobese (group C) and obese children and adolescents (group D). Copeptin levels were higher in group D (p = 0.04).Conclusion: The measurement of copeptin could represent a useful tool for the diagnostic pathway of dysnatremic conditions, but its interpretation should take into consideration the state of hydration. Furthermore, it could also be a promising marker for obesity and metabolic syndrome, although this hypothesis needs further studies to be confirmed. What is Known: • Copeptin use as a diagnostic tool in AVP-related disorders, such as diabetes insipidus or syndrome of inappropriate secretion of antidiuretic hormone, is well established in adults • In pediatric age, few studies are available, but the preliminary data, including our previous study, seems to be promising. What is New: • In this study, we represent the distribution of copeptin levels in a pediatric cohort and show the significant influence of fluid ingestion on its plasma levels. • Also BMI seems to be a significant variable on copeptin levels and may be used as an obesity marker in pediatric age.

Pro B-type Natriuretic Peptide and Midregional Proadrenomedullin are Associated with Incident Carotid Stenosis During Long Term Follow-up

BACKGROUND

Plasma biomarkers may be useful to detect healthy individuals at increased risk for atherosclerotic manifestations, such as carotid artery stenosis. The aim of this longitudinal cohort study was to evaluate new biomarkers in relation to C-reactive protein and conventional risk factors for carotid artery stenosis during long term follow-up METHODS: The following markers were measured in 5550 middle-aged subjects: C-reactive protein, lipoprotein-associated phospholipase A2, proneurotensin, midregional pro-adrenomedullin, midregional pro-atrial natriuretic peptide, N-terminal pro B-type natriuretic peptide, copeptin, and cystatin C. Subjects with prevalent carotid artery stenosis were excluded. Subjects were followed in national patient registers for 23.4 (interquartile range 19.5-24.3) years regarding incident carotid artery stenosis, both operated and non-operated.

RESULTS

When including conventional risk markers in Cox regression, N-terminal pro B-type natriuretic peptide (Hazard ratio 1.36; 95% confidence interval 1.12-1.65; p = 0.002) was independently associated with incident carotid artery stenosis, whereas there were trends for C-reactive protein (HR 1.20; 95% confidence interval 0.98-1.48; p = 0.071), and midregional pro-adrenomedullin (Hazard ratio 1.21; 95% confidence interval 0.99-1.47; p = 0.061). Midregional pro-adrenomedullin (Hazard ratio 1.30; 95% confidence interval 1.03-1.65; p = 0.029) was independently associated with incident surgery for carotid artery stenosis, whereas there was a trend for N-terminal pro B-type natriuretic peptide (Hazard ratio 1.31; 95% confidence interval 1.00-1.72; p = 0.052).

CONCLUSIONS

N-terminal pro B-type natriuretic peptide and midregional pro-adrenomedullin can be used as predictors for clinically detected carotid artery stenosis during long-term follow-up of healthy subjects.

Copeptin is not useful as a marker of malignant disease in the syndrome of inappropriate antidiuresis

OBJECTIVE

The syndrome of inappropriate antidiuresis (SIAD) is a common condition in hospitalized patients. It is crucial to establish the cause of SIAD, especially in order to exclude underlying malignancy. As malignant SIAD may be due to a paraneoplastic synthesis of arginine vasopressin, we hypothesized that its stable surrogate marker copeptin can be used as a diagnostic tool to differentiate between malignant and non-malignant SIAD.

METHODS

Prospective observational study. We analyzed data from 146 SIAD patients of two different cohorts from Switzerland and Germany. Patients were included while presenting at the emergency department and underwent a standardized diagnostic assessment including the measurement of copeptin levels.

RESULTS

Thirty-nine patients (median age: 63 years, 51% female) were diagnosed with cancer-related SIAD and 107 (median age: 73 years, 68% female) with non-malignant SIAD. Serum sodium levels were higher in cancer-related versus non-malignant SIAD: median (IQR) 124 mmol/l (120; 127) versus 120 mmol/l (117; 123) (P<0.001). Median (IQR) copeptin levels of patients with cancer-related SIAD were 11.1 pmol/l (5.2; 37.1) and 10.5 pmol/l (5.2; 25.2) with non-malignant SIAD (P = 0.38). Among different cancer entities, patients suffering from small-cell lung cancer showed the highest copeptin values, but overall no significant difference in copeptin levels between cancer types was observed (P = 0.46).

CONCLUSIONS

Copeptin levels are similar in cancer-related and non-malignant SIAD. Therefore, Copeptin does not seem to be suitable as a marker of malignant disease in SIAD.

Elevated copeptin, arterial stiffness, and elevated albumin excretion in adolescents with type 1 diabetes

OBJECTIVE

We sought to evaluate copeptin concentrations in adolescents with and without type 1 diabetes (T1D) and examine the associations between copeptin and measures of arterial stiffness and kidney dysfunction.

RESEARCH DESIGN AND METHODS

This analysis included 169 adolescents with T1D (12-19 years of age, 59% girls, mean HbA1c 9.0 ± 1.5% and diabetes duration of 8.6 ± 2.9 years), in addition to 61 controls without T1D. Arterial stiffness including carotid-femoral pulse wave velocity (CF-PWV), carotid-radial PWV (CR-PWV), augmentation index normalized to heart rate of 75 bpm (AIx@HR75), and brachial artery distensibility (BAD). Serum copeptin, urinary albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR) by serum creatinine and cystatin C were also assessed.

RESULTS

Compared to controls, adolescents with T1D had higher median (Q1-Q3) copeptin (7.5 [5.2-11.3] vs 6.4 [4.8-8.3] pmol/L, P = .01), mean ± SD eGFR (121 ± 23 vs 112 ± 16 mL/min/1.73m² , P = .002) and lower BAD (7.1 ± 1.3 vs 7.2 ± 1.2%, P = .02). Adolescents with T1D in the in high tertile copeptin group (>9.1 pmol/L) had higher AIx@HR75 (10.7 ± 1.2 vs 5 ± 1.2, P = .001), CR-PWV (5.30 ± 1.0 vs 5.18 ± 1.0 m/s, P = .04), and UACR (12 ± 1 vs 8 ± 1 mg/g, P = .025) compared to those in low tertile (<5.8 pmol/L) after adjusting for age, sex, and eGFR. Copeptin inversely associated with CF-PWV independent of age, sex, eGFR, SBP, and HbA1c in T1D adolescents.

CONCLUSIONS

Our data demonstrate that elevated copeptin was associated with worse arterial stiffness in adolescents with T1D. These findings suggest that copeptin could improve CVD risk stratification in adolescents with T1D.

Vasopressin and Copeptin in health and disease

Arginine Vasopressin (AVP) and copeptin derive from the same precursor molecule. Due to the equimolar secretion, copeptin responds as rapidly as AVP to osmotic, hemodynamic and unspecific stress-related stimuli and both peptides show a very strong correlation. The physiological functions of AVP are homeostasis of fluid balance, vascular tonus and regulation of the endocrine stress response. In contrast, the exact function of copeptin remains unknown. Since copeptin, in contrast to AVP, can easily be measured with a sandwich immunoassay, its main function so far that it indirectly indicates the amount of AVP in the circulation. Copeptin has emerged as a useful measure in different diseases. On one hand, through its characteristics as a marker of stress, it provides a unique measure of the individual stress burden. As such, it is a prognostic marker in different acute diseases such as ischemic stroke or myocardial infarction. On the other side, it has emerged as a promising marker in the diagnosis of AVP-dependent fluid disorders. Copeptin reliably differentiates various entities of the polyuria polydipsia syndrome; baseline levels >20 pmol/L without prior fluid deprivation identify patients with nephrogenic diabetes insipidus, whereas levels measured upon osmotic stimulation with hypertonic saline or upon non-osmotic stimulation with arginine differentiate primary polydipsia from central diabetes insipidus. In patients with hyponatremia, low levels of copeptin together with low urine osmolality identify patients with primary polydipsia, but copeptin levels overlap in all other causes of hyponatremia, limiting its diagnostic use in hyponatremia. Copeptin has also been put forward as predictive marker for autosomal dominant polycystic kidney disease and for diabetes mellitus, but more studies are needed to confirm these findings.

Cardiovascular biomarkers predict post-discharge re-hospitalization risk and mortality among Swedish heart failure patients

AIM

The aim of this study was to assess the predictive role of biomarkers, associated with cardiovascular stress and its neuroendocrine response as well as renal function, in relation to mortality and risk of re-hospitalization among consecutive patients admitted because of heart failure (HF).

METHODS AND RESULTS

A total of 286 patients (mean age, 75 years; 29% women) hospitalized for newly diagnosed or exacerbated HF were analysed. Associations between circulating levels of mid-regional pro-adrenomedullin (MR-proADM), copeptin, C-terminal pro-endothelin-1, N-terminal pro-brain natriuretic peptide (NT-proBNP), cystatin C, and all-cause mortality as well as risk of re-hospitalization due to cardiac causes were assessed using multivariable Cox regression models. A two-sided Bonferroni-corrected P-value of 0.05/5 = 0.010 was considered statistically significant. All biomarkers were related to echocardiographic measurements of cardiac dimensions and function. A total of 57 patients died (median follow-up time, 17 months). In the multivariable-adjusted Cox regression analyses, all biomarkers, except C-terminal pro-endothelin-1, were significantly associated with increased mortality: NT-proBNP [hazard ratio (HR) 1.85, 95% confidence interval (CI) 1.17-2.17; P = 4.0 × 10^-4 ], MR-proADM (HR 1.94, 95% CI 1.36-2.75; P = 2.2 × 10^-4 ), copeptin (HR 1.70, 95% CI 1.22-2.36; P = 0.002), and cystatin C (HR 2.11, 95% CI 1.56-2.86; P = 1.0 × 10^-6 ). A total of 90 patients were re-hospitalized (median time to re-hospitalization, 5 months). In multivariable Cox regression analyses, NT-proBNP was the only biomarker that showed significant association with risk of re-hospitalization due to cardiac causes (HR 1.43, 95% CI 1.10-1.87; P = 0.009).

CONCLUSIONS

Among patients hospitalized for HF, elevated plasma levels of NT-proBNP, MR-proADM, copeptin, and cystatin C are associated with higher mortality after discharge, whereas NT-proBNP is the only biomarker that predicts the risk of re-hospitalization due to cardiac causes.

Copeptin, B-type natriuretic peptide and cystatin C are associated with incident symptomatic PAD

Purpose: The aim of this study is to evaluate plasma biomarkers as predictors for peripheral arterial disease (PAD). Materials and methods: Prospective longitudinal cohort study of middle-aged individuals from the cardiovascular cohort of the Malmö Diet and Cancer study (MDCS) (n = 5550; 1991-94). Cystatin C, copeptin, N-terminal pro-B-type natriuretic peptide (N-BNP), midregional proatrial natriuretic peptide (MR-proANP), mid-regional proadrenomedullin (MR-proADM), and conventional risk factors were measured at baseline. The diagnosis of symptomatic PAD was validated in 97% of the cases. Results: Cumulative incidence of PAD during median follow up of 23.4 years was 4.4% (men 5.9%, women 3.3%). Adjusted for age, sex, smoking, body mass index, hypertension, diabetes mellitus and total cholesterol, copeptin (hazard ratio [HR] 1.46; 95% confidence interval [CI] 1.19-1.80), N-BNP (HR 1.28; 95% CI 1.11-1.48), and cystatin C (HR 1.19; 95% CI 1.10-1.29) were independently associated with incident PAD. Subjects with the three biomarkers copeptin, N-BNP, and cystatin C in the highest quartiles, ran a high risk of incident PAD (HR 3.29; 95% CI 1.76-6.17) compared to those with no biomarker in the highest quartile. Conclusion: Copeptin, N-BNP, and cystatin C were associated with incident symptomatic PAD, implying that these biomarkers are sensitive indicators of early subclinical PAD. Clinical significance First prospective longitudinal cohort study evaluating Cystatin C, copeptin, N-terminal pro-B-type natriuretic peptide (N-BNP), midregional proatrial natriuretic peptide (MR-proANP), and mid-regional proadrenomedullin (MR-proADM) as predictors for peripheral arterial disease (PAD). Copeptin, N-BNP, and Cystatin C where independently associated with incident symptomatic PAD after adjustment for conventional risk factors. Copeptin, N-BNP, and Cystatin C seem to be sensitive indicators of early subclinical PAD.

Copeptin and its role in the diagnosis of diabetes insipidus and the syndrome of inappropriate antidiuresis

Copeptin is secreted in an equimolar amount to arginine vasopressin (AVP) but can easily be measured in plasma or serum with a sandwich immunoassay. The main stimuli for copeptin are similar to AVP, that is an increase in osmolality and a decrease in arterial blood volume and pressure. A high correlation between copeptin and AVP has been shown. Accordingly, copeptin mirrors the amount of AVP in the circulation. Copeptin has, therefore, been evaluated as diagnostic biomarker in vasopressin-dependent disorders of body fluid homeostasis. Disorders of body fluid homeostasis are common and can be divided into hyper- and hypoosmolar circumstances: the classical hyperosmolar disorder is diabetes insipidus, while the most common hypoosmolar disorder is the syndrome of inappropriate antidiuresis (SIAD). Copeptin measurement has led to a "revival" of the direct test in the differential diagnosis of diabetes insipidus. Baseline copeptin levels, without prior thirsting, unequivocally identify patients with nephrogenic diabetes insipidus. In contrast, for the difficult differentiation between central diabetes insipidus and primary polydipsia, a stimulated copeptin level of 4.9 pmol/L upon hypertonic saline infusion differentiates these two entities with a high diagnostic accuracy and is clearly superior to the classical water deprivation test. On the contrary, in the SIAD, copeptin measurement is of only little diagnostic value. Copeptin levels widely overlap in patients with hyponatraemia and emphasize the heterogeneity of the disease. Additionally, a variety of factors lead to unspecific copeptin elevations in the acute setting further complicating its interpretation. The broad use of copeptin as diagnostic marker in hyponatraemia and specifically to detect cancer-related disease in SIADH patients can, therefore, not be recommended.

Syndrome of Inappropriate Antidiuresis

The syndrome of inappropriate antidiuresis (SIAD) is a common cause of hyponatremia in hospitalized children. SIAD refers to euvolemic hyponatremia due to nonphysiologic stimuli for arginine vasopressin production in the absence of renal or endocrine dysfunction. SIAD can be broadly classified as a result of tumors, pulmonary or central nervous system disorders, medications, or other causes such as infection, inflammation, and the postoperative state. The presence of hypouricemia with an elevated fractional excretion of urate can aid in the diagnosis. Treatment options include fluid restriction, intravenous saline solutions, oral sodium supplements, loop diuretics, oral urea, and vasopressin receptor antagonists (vaptans).

Cardiovascular biomarkers predict fragility fractures in older adults

OBJECTIVE

To assess the role of four biomarkers of neuroendocrine activation and endothelial dysfunction in the longitudinal prediction of fragility fractures.

METHODS

We analysed a population-based prospective cohort of 5415 community-dwelling individuals (mean age, 68.9±6.2 years) enrolled in the Malmö Preventive Project followed during 8.1±2.9 years, and investigated the longitudinal association between C-terminal pro-arginine vasopressin (CT-proAVP), C-terminal endothelin-1 precursor fragment (CT-proET-1), the mid-regional fragments of pro-adrenomedullin (MR-proADM) and pro-atrial natriuretic peptide (MR-proANP), and incident vertebral, pelvic and extremity fractures.

RESULTS

Overall, 1030 (19.0%) individuals suffered vertebral, pelvic or extremity fracture. They were older (70.7±5.8 vs 68.4±6.3 years), more likely women (46.9% vs 26.3%), had lower body mass index and diastolic blood pressure, were more often on antihypertensive treatment (44.1% vs 38.4%) and had more frequently history of fracture (16.3% vs 8.1%). Higher levels of MR-proADM (adjusted HR (aHR) per 1 SD: 1.51, 95% CI 1.01 to 2.28, p<0.001) and MR-proANP (aHR: 1.23, 95% CI 1.05 to 1.45, p<0.001) were independently associated with increased risk of any fracture. The fracture risk increased linearly across MR-proANP quartiles. Individuals who were in the top quartile of all four biomarkers had a significant higher risk of fracture at any site (aHR: 2.32, 95% CI 1.86 to 2.91), vertebral fracture (aHR: 3.16, 95% CI 1.97 to 5.07) and femoral fracture (aHR: 2.35, 95% CI 1.64 to 3.36).

CONCLUSIONS

Elevated levels of MR-proADM and MR-proANP independently predict fragility fractures in older adults. In subjects with top quartile levels of all four biomarkers there is a twofold to threefold increase in risk of vertebral and femoral fractures.

Cardiovascular biomarkers and risk of low-energy fractures among middle-aged men and women-A population-based study

BACKGROUND

Low-energy fractures are a growing health challenge as their incidence increases with advancing age. As cardiovascular instability may be associated with higher likelihood of traumatic falls, we aimed to investigate the associations between four cardiovascular biomarkers and the risk of low-energy fractures in a middle-aged population.

METHODS

A total of 5291 individuals from the prospective Malmö Diet and Cancer (MDC) study (mean age, 57 years; 59% women) with data on baseline levels of four cardiovascular biomarkers: mid-regional-fragment of pro-adrenomedullin-peptide (MR-pro-ADM), mid-regional-fragment of pro-atrial-natriuretic-peptide (MR-proANP), N-terminal pro-brain natriuretic peptide (NT-pro-BNP) and C-terminal-pro-arginine-vasopressin (CT-pro-AVP/Copeptin) were included. The associations between biomarker levels and first incident low-energy fracture were tested in Cox proportional-hazard models, taking potential interactions and traditional risk factors into account.

RESULTS

Participants were followed for a median time of 21.0 years, during which 1002 subjects (19%) experienced at least one low-energy fracture. Subjects with incident fracture were older, more likely to be women, had lower BMI and higher prevalence of previous fractures. Among biomarkers, there was a significant interaction between gender and MR-pro-ADM on the risk of fracture (p = 0.002). MR-pro-ADM predicted fractures in men only (hazard ratio, 1.23; 95% CI 1.09-1.40; p = 0.001), whereas there was no association among women. Levels of MR-pro-ANP, NT-pro-BNP and CT-pro-AVP did not predict fractures.

CONCLUSIONS

Higher circulating levels of MR-pro-ADM predict low-energy fractures among middle-aged-men, whereas levels of MR-pro-ANP, NT-pro-BNP and CT-pro-AVP are not associated with increased fracture risk. Further controlled studies should test the hypothesis whether MR-pro-ADM may improve prediction of bone fractures.

Plasma copeptin, kidney disease, and risk for cardiovascular morbidity and mortality in two cohorts of type 2 diabetes

Background

Cardiovascular disease and kidney damage are tightly associated in people with type 2 diabetes. Experimental evidence supports a causal role for vasopressin (or antidiuretic hormone) in the development of diabetic kidney disease (DKD). Plasma copeptin, the COOH-terminal portion of pre-provasopressin and a surrogate marker of vasopressin, was shown to be positively associated with the development and progression of DKD. Here we assessed the association of plasma copeptin with the risk of cardiovascular events during follow-up in two prospective cohorts of type 2 diabetic patients, and we examined if this association could be mediated by deleterious effects of vasopressin on the kidney.

Methods

We studied 3098 and 1407 type 2 diabetic patients from the French cohorts DIABHYCAR and SURDIAGENE, respectively. We considered the incidence during follow-up (median: 5 years) of a combined end point composed of myocardial infarction, coronary revascularization, hospitalization for congestive heart failure, or cardiovascular death. Copeptin concentration was measured in baseline plasma samples by an immunoluminometric assay.

Results

The cumulative incidence of cardiovascular events during follow-up by sex-specific tertiles of baseline plasma copeptin was 15.6% (T1), 18.7% (T2) and 21.7% (T3) in DIABHYCAR (p = 0.002), and 27.7% (T1), 34.1% (T2) and 47.6% (T3) in SURDIAGENE (p < 0.0001). Cox proportional hazards survival regression analyses confirmed the association of copeptin with cardiovascular events in both cohorts: hazard ratio with 95% confidence interval for T3 vs. T1 was 1.29 (1.04–1.59), p = 0.02 (DIABHYCAR), and 1.58 (1.23–2.04), p = 0.0004 (SURDIAGENE), adjusted for sex, age, BMI, duration of diabetes, systolic blood pressure, arterial hypertension, HbA1c, total cholesterol, HDL-cholesterol, triglycerides, estimated glomerular filtration rate (eGFR), urinary albumin concentration (UAC), active tobacco smoking, and previous history of myocardial infarction at baseline. No interaction was observed between plasma copeptin and eGFR (p = 0.40) or UAC (p = 0.61) categories on the risk of cardiovascular events in analyses of pooled cohorts.

Conclusions

Plasma copeptin was positively associated with major cardiovascular events in people with type 2 diabetes. This association cannot be solely accounted for by the association of copeptin with kidney-related traits.

Electronic supplementary material

The online version of this article (10.1186/s12933-018-0753-5) contains supplementary material, which is available to authorized users.

Release and Decay Kinetics of Copeptin vs AVP in Response to Osmotic Alterations in Healthy Volunteers

CONTEXT

Copeptin is the C-terminal fragment of the arginine vasopressin (AVP) prohormone whose measurement is more robust than that of AVP. Similar release and clearance characteristics have been suggested promoting copeptin as a surrogate marker.

OBJECTIVE

To characterize the physiology of osmotically regulated copeptin release and its half-life in direct comparison with plasma AVP.

DESIGN

Ninety-one healthy volunteers underwent a standardized three-phase test protocol including (1) osmotic stimulation into the hypertonic range by hypertonic-saline infusion followed by osmotic suppression via (2) oral water load and (3) subsequent glucose infusion. Plasma copeptin, AVP, serum sodium, and osmolality levels were measured in regular intervals.

RESULTS

In phase 1, an increase in median osmotic pressure [289 (286; 291) to 311 (309; 314) mOsm/kg H2O] caused similar release kinetics of plasma copeptin [4 (3.1; 6) to 29.3 (18.6; 48.2) pmol/L] and AVP [1 (0.7; 1.6) to 10.3 (6.8; 18.8) pg/mL]. Subsequent osmotic suppression to 298 (295; 301) mOsm/kg at the end of phase 3 revealed markedly different decay kinetics between both peptides-an estimated initial half-life of copeptin being approximately 2 times longer than that of AVP (26 vs 12 minutes).

CONCLUSION

Copeptin is released in equimolar amounts with AVP in response to osmotic stimulation, suggesting its high potential as an AVP surrogate for differentiation of osmotic disorders. Furthermore, we here describe the decay kinetics of copeptin in response to osmotic depression enabling to identify a half-life for copeptin in direct comparison with AVP.

B-type natriuretic peptide for prediction of incident clinically significant abdominal aortic aneurysm: A population-based prospective study

Pathogenesis of abdominal aortic aneurysm (AAA) is unclear. The aim of this study was to evaluate inflammatory and hemodynamic plasma biomarkers as predictors for AAA in the prospective longitudinal cohort of middle-aged individuals from the cardiovascular cohort of the Malmö Diet and Cancer Study ( n=5551; 1991–94). C-reactive protein, cystatin C, copeptin, N-terminal pro-B-type natriuretic peptide (N-BNP), midregional pro-atrial natriuretic peptide (MR-proANP) and conventional risk factors at baseline were measured in patients with incident AAA during follow-up and compared to individuals without a diagnosis of AAA. Subjects were followed until 31 December 2013. Multivariable analyses were expressed in terms of hazard ratios (HR) per 1 standard deviation increment of each respective log-transformed plasma biomarker in the Cox proportional hazard models. Mean follow-up time was 20.7 years. Cumulative incidence of AAA was 1.5% (men 2.9%, women 0.5%). Mean age of individuals with incident AAA was 59.7 years at study entry and AAA was diagnosed on average 14 years later. Adjusting for age, sex, smoking, body mass index, hypertension and diabetes mellitus, N-BNP (HR 1.29; 95% CI 1.03–1.62), but not MR-proANP (HR 1.20; 95% CI 0.95–1.50), was independently associated with incident AAA. In conclusion, the plasma biomarker N-BNP was associated with future development of AAA, which implies that this marker is a sensitive indicator of early subclinical cardiovascular disease.

Effects of hydration on plasma copeptin, glycemia and gluco-regulatory hormones: a water intervention in humans

Purpose

High plasma copeptin, a marker of vasopressin, predicts diabetes mellitus. We tested if copeptin could be suppressed by increased water intake in healthy individuals, and if a water-induced change in copeptin was accompanied by altered concentrations of glucose, insulin or glucagon.

Methods

Thirty-nine healthy individuals underwent, in random order, 1 week of high water intake (3 L/day on top of habitual intake) and 1 week of normal (habitual) fluid intake (control). Fasting plasma concentrations of copeptin, glucose, insulin and glucagon were compared between the ends of both periods. Furthermore, acute copeptin kinetics were mapped for 4 h after ingestion of 1 L of water.

Results

After acute intake of 1 L water, copeptin was significantly reduced within 30 min, and reached maximum reduction within 90 min with on average 39% reduction (95% confidence interval (95 CI) 34–45) (p < 0.001) and remained low the entire test period (4 h). One week of increased water intake led to a 15% reduction (95 CI 5–25) (p = 0.003) of copeptin compared to control week. The greatest reduction occurred among subjects with habitually high copeptin and concentrated urine (“water-responders”). Water-responders had significant water-induced reduction of glucagon, but glucose and insulin were unaffected.

Conclusions

Both acute and 1 week extra water intake potently reduced copeptin concentration. In those with the greatest decline (water-responders), who are typically low drinkers with high baseline copeptin, water induced a reduction in fasting glucagon. Long-term trials assessing the effect of water on glucometabolic traits should focus on low-water drinkers with high copeptin concentration.

Electronic supplementary material

The online version of this article (10.1007/s00394-017-1595-8) contains supplementary material, which is available to authorized users.

Prognostic and diagnostic significance of copeptin in acute exacerbation of chronic obstructive pulmonary disease and acute heart failure: data from the ACE 2 study

BACKGROUND

Copeptin is a novel biomarker that predicts mortality in lower respiratory tract infections and heart failure (HF), but the diagnostic value of copeptin in acute dyspnea and the prognostic significance of copeptin in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is not clear.

METHOD

We determined copeptin and NT-proBNP concentrations at hospital admission in 314 patients with acute dyspnea who were categorized by diagnosis. Survival was registered after a median follow-up of 816 days, and the prognostic and diagnostic properties of copeptin and NT-proBNP were analyzed in acute HF (n = 143) and AECOPD (n = 84) separately.

RESULTS

The median concentration of copeptin at admission was lower in AECOPD compared to acute HF (8.8 [5.2-19.7] vs. 22.2 [10.2-47.9]) pmol/L, p < 0.001), but NT-proBNP discriminated acute HF from non-HF related dyspnea more accurately than copeptin (ROC-AUC 0.85 [0.81-0.89] vs. 0.71 [0.66-0.77], p < 0.0001). Adjusted for basic risk factors, increased copeptin concentrations predicted mortality in AECOPD (HR per log (ln) unit 1.72 [95% CI 1.21-2.45], p = 0.003) and acute HF (1.61 [1.25-2.09], p < 0.001), whereas NT-proBNP concentrations predicted mortality only in acute HF (1.62 [1.27-2.06], p < 0.001). On top of a basic model copeptin reclassified a significant proportion of patients into a more accurate risk strata in AECOPD (NRI 0.60 [0.19-1.02], p = 0.004) and acute HF (0.39 [0.06-0.71], p = 0.020).

CONCLUSION

Copeptin is a strong prognostic marker in both AECOPD and acute HF, while NT-proBNP concentrations predict mortality only in patients with acute HF. NT-proBNP levels are superior to copeptin levels to diagnose acute HF in patients with acute dyspnea.

[Hyponatremia in emergency admissions - often dangerous]

Hyponatremia is the most common electrolyte disorder in clinical practice and associated with increased morbidity and mortality, independent of underlying disease. Untreated acute hyponatremia can cause substantial morbidity and mortality as a result of osmotically induced cerebral edema whilst over rapid correction of chronic hyponatremia can cause serious neurologic impairment and death resulting from osmotic demyelination. Still hyponatremia is often neglected and insufficiently addressed, most likely due to limited understanding of its pathophysiological mechanisms. Being familiar with only few basic principles of body fluid regulation may be a worthwhile investment into the clinical career and save patients' lives.