Dolores Limongi，Cartesio D'Agostini，Marco Ciotti*Telematic University San Raffaele Rome，Via di Val Cannuta，0067，Rome，ItalyClinical Microbiology and Virology，Polyclinic Tor Vergata Foundation，Viale Oxford 8，00，Rome，ItalyLaboratory of Molecular Virology，Polyclinic Tor Vergata Foundation，Viale Oxford 8，00，Rome，Italy

ABSTRACT

Sepsis remains a leading cause of death in the intensive care units and in all age groups worldwide. Early recognition and diagnosis are key to achieving improved outcomes. Therefore，novel biomarkers that might better inform clinicians treating such patients are surely needed. The main attributes of successful biomarkers would be high sensitivity，specificity，possibility of bedside monitoring and financial accessibility. A panel of sepsis biomarkers along with currently used laboratory tests will facilitate earlier diagnosis，timely treatment and improved outcome may be more effective than single biomarkers. In this review，we summarize the most recent advances on sepsis biomarkers evaluated in clinical and experimental studies.

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New sepsis biomarkers

Dolores Limongi1，Cartesio D'Agostini2，Marco Ciotti3*1Telematic University San Raffaele Rome，Via di Val Cannuta，00167，Rome，Italy
2Clinical Microbiology and Virology，Polyclinic Tor Vergata Foundation，Viale Oxford 81，00133，Rome，Italy3Laboratory of Molecular Virology，Polyclinic Tor Vergata Foundation，Viale Oxford 81，00133，Rome，Italy

ABSTRACT

Sepsis remains a leading cause of death in the intensive care units and in all age groups worldwide. Early recognition and diagnosis are key to achieving improved outcomes. Therefore，novel biomarkers that might better inform clinicians treating such patients are surely needed. The main attributes of successful biomarkers would be high sensitivity，specificity，possibility of bedside monitoring and financial accessibility. A panel of sepsis biomarkers along with currently used laboratory tests will facilitate earlier diagnosis，timely treatment and improved outcome may be more effective than single biomarkers. In this review，we summarize the most recent advances on sepsis biomarkers evaluated in clinical and experimental studies.

Keywords：

Biomarker

Sepsis

Plasma chitotriosidase

Presepsin

Interleukin-27

Hepcidin

Macrophage migration inhibitory factor

ARTICLE INFO

Article history：

Received 19 Dec 2015

Accepted 15 Feb 2016

Available online 20 Apr 2016

Mini review http://dx.doi.org/10.1016/j.apjtb.2016.04.005

Tel: +39 06 20902087

Fax: +39 06 20900413

E-mail: marco.ciotti@ptvonline.it

Peer review under responsibility of Hainan Medical University. The journal implements double-blind peer review practiced by specially invited international editorial board members.

1. Introduction

The first scientific definition of sepsis proposed by Schottmuller in 1914 was that sepsis is a state caused by microbial invasion from a local infectious source into the bloodstream which leads to signs of systemic illness in remote organs［1，2］. In 1992 at the Consensus Conference of the American College of Chest Physicians and the Society of Critical Care Medicine，sepsis was defined as the host's immune response［systemic inflammatory response syndrome（SIRS）］to injury and/or infectious stimuli in the presence of a known（or strongly suspected）infection［3］. The same consensus group also defined criteria to qualify SIRS，which schematized the host inflammatory response to infection，trauma，ischemiareperfusion injury and burns. Moreover，in 2001，this same conference modified the SIRS definition by expanding the list of signs and symptoms of sepsis to reflect clinical bedside experience［4］. Sepsis remains a leading cause of death in the intensive care units and in all age groups worldwide. In Europe，every year，157 000 people die for this systemic multi-organs failure as a consequence of bacterial or fungal infection［5］.

The septic response is an extremely complex chain of events involving inflammatory and anti-inflammatory processes，humoral and cellular reactions and circulatory abnormalities［6，7］. The incidence of sepsis is increasing due to multiple factors，including the aging of the population，the performance of more invasive procedures and the continuing emergence of antibiotic-resistant microorganisms［8］. In some cases，the diagnosis is challenging. An early diagnosis of sepsis helps to enable rapid treatment，improve outcomes and reduce unnecessary antibiotic therapy. Diagnostic biomolecular markers could greatly simplify，accelerate and objectify the entire healing process，from diagnosis and process monitoring to verification and timely correction of therapy. At present，there is no ideal and clinical gold standard for the diagnosis of sepsis，as microbiology is not sensitive enough and laboratory tests are unspecific for use as a reference standard［9-11］.

Biomarkers can have an important role in this process because they can indicate the presence or absence or severity of sepsis and have the potential to serve a crucial role by providing adjunctive information to guide clinicians to rapid diagnosis and extension of treatment beyond the standard therapy［12，13］. This review will discuss the major biomarkers of sepsis.

2. Sepsis biomarkers

Biomarkers are a valuable tool in facilitating early diagnosis，identification of patients at high risk of complications and in monitoring disease progression. These assessments are critical for establishing an appropriate therapy and improving patient outcomes. An ideal biomarker provides indirect but ongoing information（determinations）of disease activity.

In 2010，Pierrakos and Vincent estimated that at least 178 different sepsis biomarkers have been reported in the literature ［14］. Five years later，that number is likely higher.

3. Plasma chitotriosidase（ChT）activity

ChT，a member of the mammalian chitinase family，structurally homologous to chitinases from other species，is synthesized and secreted by specifically activated macrophages. ChT was found to be an excellent marker for lipid laden macrophages in Gaucher patients and is now widely used to assist clinical management of patients［14，15］. Moreover，an increased ChT has been noted in other inherited lysosomal storage disorders including atherosclerosis，malaria，hematological disorders and other conditions where activated macrophages are involved ［15-17］. ChT was previously proposed to quantify the severity of sepsis. In a complex surgical case，with prolonged sepsis and consistently high ChT，it was found that the least increased values occurred in stages of extreme illness，with profound hypocholesterolemia.

ChT in sepsis should be better characterized，correlated to other biomarkers and to clinical events before becoming a reliable biomarker of septic evolution that could be implemented for patient management and decision process［18］.

4. Presepsin

Presepsin is a novel promising marker for diagnosing and monitoring sepsis. Presepsin is a 13-kDa protein that is the truncated N-terminal fragment of cluster of differentiation 14 （CD14），the receptor for lipopolysaccharide（LPS）/LPS binding protein complexes. CD14 activates the toll-like receptor 4 proinflammatory cascade in the presence of infectious agents. Two forms of CD14 are membrane CD14 and soluble CD14 （sCD14）. Complex LPS-LPS binding protein-CD14 is shed into the circulation and plasma protease generates sCD14 molecule called sCD14 subtype-presepsin. Presepsin is generated as the body response to bacterial infection and its production is induced by phagocytosis of bacteria. So，the level of presepsin should reflect the severity of infection rather than the degree of inflammation［19，20］. Some clinical studies showed that level of sCD14 increased in septic patients and it is not significantly different between patients with Gram-positive and Gramnegative infection［21-25］. This biomarker shows high specificity，and results from experimental and clinical studies are reinforcing the proof of concept［26］. Presepsin appears to be the most promising new biomarker for early diagnosis of sepsis and a better prognostic biomarker than procalcitonin.

5. Interleukin（IL）-27

A revision of the literature showed that ILs have been long investigated as potential biomarkers of sepsis. For instance，IL-6 has been evaluated as biomarker of the severity of sepsis. A recent study pointed out that IL-27 could be used as novel biomarker of sepsis in critically ill children［27］.

IL-27 was first discovered in 2002 as a new member of the IL-12 cytokine family［28］. IL-27 is a heterodimeric cytokine produced by antigen presenting cells upon exposure to microbial products and inflammatory stimuli［29，30］.

In a recent study，Hanna et al. showed that IL-27 may serve as a useful biomarker in estimating risk of bacterial infection among critically ill paediatric patients with bloodstream infections［31］. In particular，among those classified as immunecompromised，this diagnostic biomarker may be useful either alone or using a combination strategy with other available biomarkers. So，although further research is warranted，IL-27 exhibited high specificity and positive predictive values for bacterial infection in critically ill children. It has been also demonstrated that a combination of IL-27 and procalcitonin （PCT）improves the overall ability to predict infection，compared with that of either biomarker alone.

6. Hepcidin

Current research has expanded the diagnostic implications of hepcidin in other medical conditions，especially hepcidin is indicated as a potential acute-phase biomarker in inflammation and sepsis. Hepcidin is a novel peptide hormone of hepatic origin and it has a crucial role in iron metabolism interfering with the access of microorganism to iron. The synthesis of hepcidin in the liver is induced by IL-6 in response to inflammation and abnormal serum levels have been observed in different diseases and sepsis［32，33］. Recently，Cizmeci et al. showed that hepcidin is a reliable biological marker of early-as well as late-onset sepsis in neonates［34］. The serum hepcidin values were in keeping with the disease process in late-onset neonatal sepsis. A four-fold rise of serum hepcidin during sepsis returned to normal levels following therapy suggesting its use as marker of late-onset neonatal sepsis［35］.

7. Macrophage migration inhibitory factor（MIF）

MIF is a pleiotropic immune regulatory cytokine whose effect on arresting random immune cell movement was already recognized decades ago. Multiple studies have pointed to the utility of MIF as a biomarker for different diseases that have an inflammatory component and these include systemic infections and sepsis，cancer，autoimmune diseases as well as different metabolic disorders. MIF has a chemokine-like function and promotes the directed migration and recruitment of leukocytes into infectious and inflammatory sites［36］. MIF is produced by a variety of cell types in addition to immune cells such as monocytes/macrophages，B- and T-cells including endocrine，endothelial and epithelial cells［37］. It is rapidly released in response to stimuli such as microbial products，proliferative signals and hypoxia［38］. Some studies showed that MIFplasma concentrations can be elevated in patients with severe sepsis when compared to healthy control individuals［39-44］. A study conducted by Gando et al. showed that elevations of MIF and tumor necrosis factor-α were both related to poor prognosis and mortality in patients with intravascular disseminated coagulation with systematic inflammation compared to non-intravascular disseminated coagulation patients［45］. However，when compared to other infectious biomarkers，MIF had a limited value as single marker compared to C-reactive protein（CRP）or PCT，which exhibited superior diagnostic characteristics［45］. So，MIF seems to have a greater diagnostic value when used in combination with other biomarkers rather than alone. This observation is in line with another study where the high measured levels of MIF and PCT correlated with lethal outcome in severe burned patients［46］.

8. Conclusions

Several potential biomarkers of sepsis and inflammation have been identified and investigated in recent years，but none of them has sufficient specificity or sensitivity to characterize by itself the presence of an infection and the complexity of the inflammatory and immune processes involved，and therefore to be routinely employed in clinical practice. A combination of several sepsis biomarkers may be more effective.

Conflict of interest statement

We declare that we have no conflict of interest.

References

［1］Schottmueller H.［Nature and treatment of sepsis］. Inn Med 1914；31: 257-80. German.

［2］Reinhart K，Bauer M，Riedemann NC，Hartog CS. New approaches to sepsis: molecular diagnostics and biomarkers. Clin Microbiol Rev 2012；25（4）: 609-34.

［3］American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference: definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Crit Care Med 1992；20（6）: 864-74.

［4］Levy MM，F(xiàn)ink MP，Marshall JC，Abraham E，Angus D，Cook D，et al. 2001 SCCM/ESICM/ACCP/ATS/SIS International Sepsis Definitions Conference. Crit Care Med 2003；31（4）: 1250-6.

［5］Goto M，Al-Hasan MN. Overall burden of bloodstream infection and nosocomial bloodstream infection in North America and Europe. Clin Microbiol Infect 2013；19（6）: 501-9.

［6］Hotchkiss RS，Karl IE. The pathophysiology and treatment of sepsis. N Engl J Med 2003；348（2）: 138-50.

［7］Gullo A，Bianco N，Berlot G. Management of severe sepsis and septic shock: challenges and recommendations. Crit Care Clin 2006；22（3）: 489-501. ix.

［8］Coelho FR，Martins JO. Diagnostic methods in sepsis: the need of speed. Rev Assoc Med Bras 2012；58（4）: 498-504.

［9］Wacker C，Prkno A，Brunkhorst FM，Schlattmann P. Procalcitonin as a diagnostic marker for sepsis: a systematic review and metaanalysis. Lancet Infect Dis 2013；13（5）: 426-35.

［10］Su LX，F(xiàn)eng L，Song Q，Kang HJ，Zhang XG，Liang ZX，et al. Diagnostic value of dynamics serum sCD163，sTREM-1，PCT，and CRP in differentiating sepsis，severity assessment，and prognostic prediction. Mediat Inflamm 2013；2013: 969875.

［11］Jaimes FA，De La Rosa GD，Valencia ML，Arango CM，Gomez CI，Garcia A，et al. A latent class approach for sepsis diagnosis supports use of procalcitonin in the emergency room for diagnosis of severe sepsis. BMC Anesthesiol 2013；13（1）: 23.

［12］Biomarkers Definitions Working Group. Biomarkers and surrogate endpoints: preferred definitions and conceptual framework. Clin Pharmacol Ther 2001；69（3）: 89-95.

［13］Marshall JC，Reinhart K. International sepsis forum. Biomarkers of sepsis. Crit Care Med 2009；37（7）: 2290-8.

［14］Pierrakos C，Vincent JL. Sepsis biomarkers: a review. Crit Care 2010；14（1）: R15.

［15］Malaguarnera L. Chitotriosidase: the yin and yang. Cell Mol Life Sci 2006；63（24）: 3018-29.

［16］Cho SJ，Weiden MD，Lee CG. Chitotriosidase in the pathogenesis of inflammation，interstitial lung diseases and COPD. Allergy Asthma Immunol Res 2015；7（1）: 14-21.

［17］Chiarla C，Giovannini I，Antuzzi D，Piras A，Ardito F，Giuliante F. Clinical use of plasma chitotriosidase in severe sepsis. Curr Med Res Opin 2016；32（2）: 273-6.

［18］Shirakawa K，Naitou K，Hirose J，Takahashi T，F(xiàn)urusako S. Presepsin（sCD14-ST）: development and evaluation of one-step ELISA with a new standard that is similar to the form of presepsin in septic patients. Clin Chem Lab Med 2011；49（5）: 937-9.

［19］Shozushima T，Takahashi G，Matsumoto N，Kojika M，Okamura Y，Endo S. Usefulness of presepsin（sCD14-ST）measurements as a marker for the diagnosis and severity of sepsis that satisfied diagnostic criteria of systemic inflammatory response syndrome. J Infect Chemother 2011；17（6）: 764-9.

［20］Endo S，Suzuki Y，Takahashi G，Shozushima T，Ishikura H，Murai A，et al. Usefulness of presepsin in the diagnosis of sepsis in a multicenter prospective study. J Infect Chemother 2012；18（6）: 891-7.

［21］Yaegashi Y，Shirakawa K，Sato N，Suzuki Y，Kojika M，Imai S，et al. Evaluation of a newly identified soluble CD14 subtype as a marker for sepsis. J Infect Chemother 2005；11（5）: 234-8.

［22］Endo S，Suzuki Y，Takahashi G，Shozushima T，Ishikura H，Murai A，et al. Presepsin as a powerful monitoring tool for the prognosis and treatment of sepsis: a multicenter prospective study. J Infect Chemother 2014；20（1）: 30-4.

［23］Masson S，Caironi P，Spanuth E，Thomae R，Panigada M，Sangiorgi G，et al. Presepsin（soluble CD14 subtype）and procalcitonin levels for mortality prediction in sepsis: data from the Albumin Italian Outcome Sepsis trial. Crit Care 2014；18（1）: R6.

［24］Novelli G，Morabito V，F(xiàn)erretti G，Pugliese F，Ruberto F，Venuta F，et al. Pathfast presepsin assay for early diagnosis of bacterial infections in surgical patients: preliminary study. Transpl Proc 2013；45（7）: 2750-3.

［25］Chenevier-Gobeaux C，Borderie D，Weiss N，Mallet-Coste T，Claessens YE. Presepsin（sCD14-ST），an innate immune response marker in sepsis. Clin Chim Acta 2015；450: 97-103.

［26］Henriquez-Camacho C，Losa J. Biomarkers for sepsis. Biomed Res Int 2014；2014: 547818.

［27］Wong HR，Cvijanovich NZ，Hall M，Allen GL，Thomas NJ，F(xiàn)reishtat RJ，et al. Interleukin-27 is a novel candidate diagnostic biomarker for bacterial infection in critically ill children. Crit Care 2012；16（5）: R213.

［28］Pflanz S，Timans JC，Cheung J，Rosales R，Kanzler H，Gilbert J，et al. IL-27，a heterodimeric cytokine composed of EBI3 and p28 protein，induces proliferation of naive CD4+T cells. Immunity 2002；16（6）: 779-90.

［29］Wojno ED，Hunter CA. New directions in the basic and translational biology of interleukin-27. Trends Immunol 2012；33（2）: 91-7.

［30］Bosmann M，Ward PA. Modulation of inflammation by interleukin-27. J Leukoc Biol 2013；94（6）: 1159-65.

［31］Hanna WJ，Berrens Z，Langner T，Lahni P，Wong HR. Interleukin-27: a novel biomarker in predicting bacterial infection among the critically ill. Crit Care 2015；19: 378.

［32］Nemeth E，Ganz T. The role of hepcidin in iron metabolism. Acta Haematol 2009；122（2-3）: 78-86.

［33］Yapak?i E，Tarcan A，Celik B，Ozbek N，G¨urakan B. Serum prohepcidin levels in term and preterm newborns with sepsis. Pediatr Int 2009；51（2）: 289-92.

［34］Cizmeci MN，Kara S，Kanburoglu MK，Simavli S，Duvan CI，Tatli MM. Detection of cord blood hepcidin levels as a biomarkerfor early-onset neonatal sepsis. Med Hypotheses 2014；82（3）: 310-2.

［35］Wu TW，Tabangin M，Kusano R，Ma Y，Ridsdale R，Akinbi H. The utility of serum hepcidin as a biomarker for late-onset neonatal sepsis. J Pediatr 2013；162（1）: 67-71.

［36］Bernhagen J，Krohn R，Lue H，Gregory JL，Zernecke A，Koenen RR，et al. MIF is a noncognate ligand of CXC chemokine receptors in inflammatory and atherogenic cell recruitment. Nat Med 2007；13（5）: 587-96.

［37］Calandra T，Roger T. Macrophage migration inhibitory factor: a regulator of innate immunity. Nat Rev Immunol 2003；3（10）: 791-800.

［38］Simons D，Grieb G，Hristov M，Pallua N，Weber C，Bernhagen J，et al. Hypoxia-induced endothelial secretion of macrophage migration inhibitory factor and role in endothelial progenitor cell recruitment. J Cell Mol Med 2011；15（3）: 668-78.

［39］Calandra T，Echtenacher B，Roy DL，Pugin J，Metz CN，H¨ultner L，et al. Protection from septic shock by neutralization of macrophage migration inhibitory factor. Nat Med 2000；6（2）: 164-70.

［40］Lehmann LE，Novender U，Schroeder S，Pietsch T，von Spiegel T，Putensen C，et al. Plasma levels of macrophage migration inhibitory factor are elevated in patients with severe sepsis. Intensive Care Med 2001；27（8）: 1412-5.

［41］Bozza FA，Gomes RN，Japiass′u AM，Soares M，Castro-Faria-Neto HC，Bozza PT，et al. Macrophage migration inhibitory factor levels correlate with fatal outcome in sepsis. Shock 2004；22（4）: 309-13.

［42］de Mendon?a-Filho HT，Gomes RV，de Almeida Campos LA，Tura B，Nunes EM，Gomes R，et al. Circulating levels of macrophage migration inhibitory factor are associated with mild pulmonary dysfunction after cardiopulmonary bypass. Shock 2004；22（6）: 533-7.

［43］Lehmann LE，Weber SU，F(xiàn)uchs D，Book M，Klaschik S，Schewe JC，et al. Oxidoreductase macrophage migration inhibitory factor is simultaneously increased in leukocyte subsets of patients with severe sepsis. Biofactors 2008；33（4）: 281-91.

［44］Kofoed K，Andersen O，Kronborg G，Tvede M，Petersen J，Eugen-Olsen J，et al. Use of plasma C-reactive protein，procalcitonin，neutrophils，macrophage migration inhibitory factor，soluble urokinase-type plasminogen activator receptor，and soluble triggering receptor expressed on myeloid cells-1 in combination to diagnose infections: a prospective study. Crit Care 2007；11（2）: R38.

［45］Gando S，Sawamura A，Hayakawa M，Hoshino H，Kubota N，Nishihira J. High macrophage migration inhibitory factor levels in disseminated intravascular coagulation patients with systemic inflammation. Inflammation 2007；30（3-4）: 118-24.

［46］Grieb G，Simons D，Piatkowski A，Bernhagen J，Steffens G，Pallua N. Macrophage migration inhibitory factor-A potential diagnostic tool in severe burn injuries？Burns 2010；36（3）: 335-42.

*Corresponding author:Marco Ciotti，Laboratory of Molecular Virology，Polyclinic Tor Vergata Foundation，Viale Oxford 81，00133，Rome，Italy.