Study of plasma copeptin level as a prognostic marker in respiratory failure patients admitted in the ICU at Benha University Hospital
Authors: Salahy Mahmoud M. Al , Elmahdy Mohammad A. , Gouda Tahany M. , Belal Khaled M. , Elnahas Shiemaa M. 
Published: September 2023

Abstract
Background
Arginine vasopressin (AVP), produced by hypothalamic neurons, is released during stress following different stimuli such as hypotension, hypoxia, hyperosmolarity, acidosis, and infections. Measurement of AVP levels has limitations because of its short half-life and instability. Copeptin, the carboxy-terminal part of the precursor (prepro-AVP), is a more stable peptide and mirrors AVP concentrations.

Aim
The aim of this work was to study the usefulness of plasma copeptin as a predictor of prognosis and outcome of respiratory failure patients admitted in the ICU.

Patients and methods
This prospective study was carried out on 45 patients (38 patients admitted at Benha University Hospital ICU and Chest Department and seven healthy patients). They were classified into three groups: group A (ICU patients) comprised 30 patients admitted with respiratory failure due to different chest diseases; group B (in-patients) comprised eight patients selected from those hospitalized at Chest Department because of respiratory failure and with no need for ICU admission as a positive control group; and group C comprised seven healthy patients included as a negative control group. All patients were submitted to full clinical history and physical examination at ICU admission, as well as available preadmission clinical data, pulmonary function tests, chest radiography if done, arterial blood gases, ECG, and clinical lab data; blood samples were taken and plasma was separated and copeptin level was measured by sandwich immunoluminometric assay.

Results
There was a statistically significant difference among studied groups as regards plasma copeptin level, which was higher in ICU patients (group A) than in in-patients (group B) and healthy control patients (group C) (P<0.001). There was a statistically significant correlation between copeptin level and both Glasgow Coma Scale and Acute Physiology and Chronic Health Evaluation II (APACHE II) score (P<0.001). The relation with Glasgow Coma Scale was negative, whereas that with Acute Physiology and Chronic Health Evaluation II score was positive. There was a statistically significant positive correlation between mean copeptin level and patients’ outcome, as its level was markedly higher in nonsurvivors (80.6+31.6) than in survivors (30.5+17.3) (P<0.001), substantiating it as a prognostic marker in critically ill patients. In ICU patients copeptin levels less than 55 pg/ml predict good prognosis and survival among ICU patients, with a sensitivity of 88.2% and a specificity of 84.6%.

Conclusion
Elevated plasma copeptin levels reflect disease severity and predict short-term mortality. Copeptin concentrations are strongly related to hypoxia, as they increase markedly with low blood oxygen concentration. Elevated plasma copeptin levels predict long hospital and ICU stay. Plasma copeptin levels increased progressively with the development of complications in ICU patients.