Sepsis and septic shock represent a leading cause of mortality in the Emergency Department (ED) and in the Intensive Care Unit (ICU). For these life-threating conditions, different diagnostic and prognostic biomarkers have been studied. Proadrenomedullin (MR-proADM) is a biomarker that can predict organ damage and the risk of imminent death in patients with septic shock.
1. Introduction
Sepsis and septic shock are life-threatening medical emergencies characterized by severe systemic inflammation and organ dysfunction due to an excessive response to infections that may lead to death
[1][2][3][4][5][6]. The definition of sepsis includes a dysregulated systemic inflammation, acute multi-organ dysfunction (i.e., cardiovascular, respiratory, and renal systems), and a deregulated immune response to a microbial invasion of the blood that is responsible of organ failure
[7][8][9][10]. The mortality rate ranges from 15–25%
[7]. Septic shock is sepsis characterized by a state of hypotension and hyperlactatemia, refractory to adequate fluid volume resuscitation that leads to hypoperfusion abnormalities, oliguria, and the alteration of mental status
[7]. Septic shock has a mortality rate that ranges from 30–50%
[7]. The early identification of sepsis and septic shock is essential for immediate treatment
[1][2] and for the reduction of the patient mortality rate
[10][11]. Sepsis can affect people of all ages
[2][3][4]. Therapy for sepsis should be personalized and tailored according to the patient’s needs. Many biomarkers such as procalcitonin (PCT) or interleukin (IL)-6 or IL-18 are used in clinical practice to facilitate the diagnosis of sepsis
[5][6]. Novel biomarkers such as proadrenomedullin (MR-proADM), kallistatin, testican-1, and presepsin have been introduced to assess the severity of sepsis and to predict the organ damage and the risk of imminent death
[5].
2. Role of MR-proADM in ICU and in ED
Several authors have investigated the role of MR-proADM in patients with sepsis and septic shock. MR-proADM is a stable and detectable fragment of 48-amino acids derived from ADM (a 52-amino acid peptide and member of the calcitonin family) that is mainly produced by vascular endothelial cells and smooth muscle cells. ADM and MR-proADM have effects on vasodilatation (on artery and vein), natriuresis, bronchodilatation, and they have influences on cardiac contractility and glomerular filtration
[11], which are involved in some clinical manifestations of sepsis and septic shock as refractory hypotension. MR-proADM has a half-life that is longer than ADM and can be more easily detected in blood compared to ADM, which is rapidly cleared from the circulation.
Most of the reported studies found that MR-proADM was a reliable biomarker that could serve as an early predictor of high mortality risk. In fact, levels of MR-proADM can potentially reflect the severity of organ dysfunction, even in the first stages of the disease, in the progression of systemic inflammatory response, in the movement from sepsis to septic shock, and in the mortality risk of septic patients
[11][12]. A prospective observational study conducted with 213 septic patients showed that MR-proADM was able to predict system dysfunction (respiratory, coagulation, renal, neurological, and cardiovascular) and was well-correlated with Sequential Organ Failure Assessment (SOFA) score components
[13]. The same results were obtained by Onal et al.
[11], who concluded that MR-proADM could be a good alternative to SOFA score. L. Buendgens and his team
[14] designed a prospective study to assess the role of MR-proADM in a cohort of 203 ICU patients and 66 healthy controls that they followed for a period of 26 months. They demonstrated that MR-proADM values were higher in critically ill patients—especially in those with sepsis progression—with a close correlation with other markers of systemic inflammation and endothelial dysfunction. Moreover, MR-proADM levels correlated with scores for disease severity (Acute Physiology and Chronic Health Disease Classification System (APACHE II), SOFA, and Simplified Acute Physiology Score (SAPS2)). The best cut-off value that was found by these authors to identify patients at high mortality risk was of 1.4 nmol/L
[14]. Similar results were also reported by Gonzales Del Castillo et al.
[15] in a larger study of 684 patients admitted to the ED for a suspected infection.
The abovementioned authors found that MR-proADM was able to identify those hiding an underlying severe condition and who were at high risk for delayed or insufficient initial treatment. In addition, authors compared several biomarkers (MR-proADM, C-reactive protein (CRP), PCT, and lactate) and clinical scores (SOFA, quick SOFA, and National early warning score (NEWS)), concluding that MR-proADM could help identify patients with low NEWS or quick SOFA values but who were at high risk for sepsis progression, helping in the initial treatment choices
[15]. A prospective observational study of 657 patients with an acute infection conducted by Haang et al.
[16] reported that the combination of MR-proADM and SOFA-score would better improve the stratification risk of patients for 30-day mortality (area under the curve (AUC) 0.87) than the SOFA-score alone (AUC 0.81). The authors defined a MR-proADM threshold value of 1.75 nmol/L as a prognostic value for 30-day mortality (sensitivity 81%, specificity 75%, and negative predictive value 98%)
[16]. The summary of studies exploring the role of MR-proADM can be seen in
Table 1.
Table 1. Summary of studies exploring the role of proadrenomedullin (MR-proADM).