suPAR (soluble uPAR) is a protein measurable in blood. The concentration of suPAR reflects the level of activation of the immune system. All humans have a suPAR baseline level which is individually determined and increases with age.
The suPAR blood level is stable with no diurnal variation and no changes following fasting. The level increases or decreases with the progression and improvement of a disease, respectively.
Elevated suPAR levels reflects inflammation, disease progression, and risk of mortality in acute and chronic diseases3-16.
Measuring suPAR levels can thus serve as a marker to determine who can be classified into low-risk category and their chances for survival upon hospital admission.
suPAR can also be used for monitoring for prevention of disease progression and earlier intervention time point.
An individual’s suPAR level can serve as a marker to determine who can be classified in the low-risk category where the chance of survival is high, and who should be placed in the high-risk category, where the risk of a poor clinical outcome is elevated.
How suPAR helps in decision-making?
When risk-stratifying unselected acute medical patients in the Emergency Department this information is useful to the clinicians for deciding who should be discharged and who should be admitted.
suPAR can also be used as a monitoring marker to prevent disease progression and decide on a change in intervention time points.
The suPAR level is elevated across diseases and not solely associated with one specific disease. Therefore, suPAR is applicable as a prognostic marker and not as a diagnostic marker.
suPAR in Triage
The normal suPAR plasma level is below 4 ng/mL in healthy individuals, about 4-6 ng/mL in unselected patients in Emergency Departments, and above 6 ng/mL in critically ill patients.
A low suPAR level indicates a good prognosis and supports the decision to discharge the patient.
A high suPAR level indicates the presence, progression, and severity of disease, and supports further clinical attention.
The suPAR level can be used for triage in the hospital’s Emergency Department and measured using the suPARnostic® products, the only CE-IVD certified product range applied for clinical determination of suPAR.
By using suPARnostic® in the triage process, the performance of the Emergency Department is significantly improved. suPARnostic® can identify 22% more patients that can be sent home without hospitalization and help to avoid unnecessary treatments and readmissions.2
Figure 1. Schematic representation of uPA receptor. The GPI-anchor links uPAR to the cell membrane making it available for uPA to bind to the receptor (1 A). When the receptor is cleaved between the GPI-anchor and D3, it becomes soluble (suPAR) (1 B). suPAR is a stable protein that can be measured in various body fluids. uPAR: uPA receptor, suPAR: soluble uPAR, 1: Domain 1, D2: Domain 2, D3: Domain
The suPAR protein
suPAR is the soluble form of the cell membrane-bound protein uPAR, a three-domain receptor23 mainly expressed on immune cells, including neutrophils, activated T-cells, macrophages, endothelial cells, and smooth muscle cells.
uPAR is released during inflammation or immune activation, and therefore the suPAR level reflects the extent of immune activation in the individual.
The membrane-bound uPAR is illustrated in Figure 1. uPAR is linked to the cell membrane by a glycosylphosphatidylinositol (GPI)-anchor. The binding of uPA to uPAR facilitates cleavage of the anchor and hence, shedding the receptor.23
Consequently, once this anchor is cleaved, the protein is released from the membrane and becomes soluble.
The History of suPAR
Originally, uPAR was proven as a receptor for uPA, which splits plasminogen into active plasmin. Moreover, uPAR interacts with other proteins and plays a role in several essential cell processes like migration, adhesion, angiogenesis, proliferation, and chemotaxis.1
Which diseases is suPAR associated with?
The suPAR protein was discovered in 1991 when it was found to be a marker of cancer progression.1 In recent years, multiple studies have shown that suPAR is also associated with several chronic diseases including cardiovascular, hepatic, renal, and pulmonary diseases.3-13 An elevated suPAR-level is also associated with a negative outcome of various infectious diseases including tuberculosis, HIV, malaria, sepsis, meningitis, and pneumonia1, 8-22 , as well as with the outcome of critically ill patients. 16
Given its possibilities, because suPAR reflects the level of chronic inflammation, it has been studied intensively as a potential marker of the development of diseases. Studies have shown that an elevated level predicts the development of chronic diseases and cancer in the general population. 3-16
“it is essential to have the help of biomarkers, such as suPAR, which can support the discharge decision”
Juan González del Castillo,
Dr PhD, Hospital Clínico San Carlos, Spain
suPAR News Vol. 1, April 2019
suPARnostic® Patient Case Stories
A healthy male, age 50, suddentlyexperienced weight loss and general non-well-being. All blood parameters were normal. His suPAR value, however, was risingand hit a critical level after approx. 6 months. Although still labelled “healthy” by the medical system, he shortly after was admitted to ICU and diagnosed with liver failure. The patient did not survive and was post-mortem diagnosed with Q-fever, a tropical disease.More elaborate tests including suPAR only one month earlier would most likely have saved this person’s life, as it would earlier have been revealed he was suffering from a critical disease.
A healthy male, age 25 years, experienced sickness and symptoms like paleness and fatigue. Repeated visits to the General Practitioner resulted in no diagnosis. All blood values were normal, and no further tests were authorized.
The slowly rising suPAR value, however, predicted that this person was developing a potentially critical condition. At a suPAR level of 4.1 ng/mL, the person was admitted to an emergency department. A series of more elaborate tests diagnosed this person with latent tuberculosis and mononucleosis.
As a result of the early recognition, the person did not require hospitalization or drug treatment. Later recognition might have involved sick days, medical treatment, and hospitalization days.
A healthy male, age 45, experienced sickness, sudden weight loss and fatigue.Blood values were normal, and the person’s suPAR level was slightly, but not critically, elevated.Adjustment of lifestyle including more sleep, better food, and more sports lowered the suPAR level, which in a period of a few months was reduced to the normal baseline.