A new turbidimetric immunoassay for serum calprotectin for fully automatized clinical analysers

Calprotectin as a sepsis diagnostic marker in critical care: a retrospective observational study

Diagnosing sepsis in critical care remains a challenge due to the lack of gold-standard diagnostics. Calprotectin (S100A8/A9) has been proposed as a diagnostic marker to identify sepsis in critically ill patients. This study evaluated the diagnostic performance of calprotectin and C-reactive protein (CRP) to distinguish between sepsis and non-sepsis on intensive care unit (ICU) admission. Admission biobank blood samples from adult patients admitted to four ICUs (2015-2018) were used to analyse calprotectin and CRP. All adult patients were screened retrospectively for the sepsis-3 criteria at ICU admission. The diagnostic performance of calprotectin and CRP was evaluated using receiver operating characteristic (ROC) curves. We included 4732 patients, of whom 44% had sepsis. Calprotectin levels were higher in sepsis (p < 0.001). The area under the receiver operating curve (AUROC) to diagnose sepsis was 0.61 for calprotectin compared to 0.72 for CRP (p < 0.001). Among microbiological subgroups of sepsis patients, fungal sepsis had the highest level of calprotectin. We conclude that the diagnostic performance of calprotectin in identifying sepsis patients at ICU admission was inferior to that of CRP.

Serum calprotectin correlates stronger with inflammation and disease activity in ACPA positive than ACPA negative rheumatoid arthritis

OBJECTIVES

The aim of the present study was to evaluate the performance of serum and SF levels of the granulocyte protein calprotectin as an inflammatory biomarker in RA patients with knee synovitis.

METHODS

Seventy-six RA patients with ongoing knee synovitis were included. Data on DAS with 28 joints and their subcomponents and radiological destruction of the affected knee were collected. White blood cell count, CRP, ACPA against cyclic citrullinated peptide version 2 (anti-CCP2), IgM RF and calprotectin were analysed in parallel in circulation and in SF. Counts of polynuclear and mononuclear cells were measured in SF.

RESULTS

Serum (S)-calprotectin correlated more strongly than SF-calprotectin with inflammatory markers and disease activity. Instead, SF-calprotectin showed a strong correlation to SF counts of white blood cells, and especially to polymorphonuclear cell counts (Spearman's ρ = 0.72, P < 0.001). S-calprotectin showed markedly stronger correlation with inflammatory markers and disease activity in ACPA positive as compared with ACPA negative RA patients; a similar difference was observed for patients with and without IgM RF.

CONCLUSION

The particularly strong association between circulating calprotectin and inflammation in ACPA positive RA is a new argument for a specific role for polymorphonuclear granulocytes/neutrophils in this RA subset. Measurement of calprotectin in SF does not convey any additional benefit compared with measurement in the circulation in RA patients with knee synovitis.

Rapid prediction of acute thrombosis via nanoengineered immunosensors with unsupervised clustering for multiple circulating biomarkers

The recent SARS-CoV-2 pandemic underscores the need for rapid and accurate prediction of clinical thrombotic events. Here, we developed nanoengineered multichannel immunosensors for rapid detection of circulating biomarkers associated with thrombosis, including C-reactive protein (CRP), calprotectin, soluble platelet selectin (sP-selectin), and D-dimer. We fabricated the immunosensors using fiber laser engraving of carbon nanotubes and CO2 laser cutting of microfluidic channels, along with the electrochemical deposition of gold nanoparticles to conjugate with biomarker-specific aptamers and antibody. Using unsupervised clustering based on four biomarker concentrations, we predicted thrombotic events in 49 of 53 patients. The four-biomarker combination yielded an area under the receiver operating characteristic curve (AUC) of 0.95, demonstrating high sensitivity and specificity for acute thrombosis prediction compared to the AUC values for individual biomarkers: CRP (0.773), calprotectin (0.711), sP-selectin (0.683), and D-dimer (0.739). Thus, a nanoengineered multichannel platform with unsupervised clustering provides accurate and efficient methods for predicting thrombosis, guiding personalized medicine.

Increasing plasma calprotectin (S100A8/A9) is associated with 12-month mortality and unfavourable functional outcome in critically ill COVID-19 patients

BACKGROUND

Calprotectin (S100A8/A9) is a pro-inflammatory mediator primarily released from neutrophils. Previous studies have revealed associations between plasma calprotectin, disease severity and in-hospital mortality in unselected COVID-19 patients.

OBJECTIVE

We aimed to assess whether plasma calprotectin dynamics during the first week of intensive care are associated with mortality and functional outcome in critically ill COVID-19 patients.

METHODS

This prospective study included 498 COVID-19 patients admitted to six intensive care units (ICUs) in Sweden between May 2020 and May 2021. Blood samples were collected on ICU admission and on day 7. The primary outcome was 12-month mortality. Secondary outcomes were functional outcome of survivors at 3 and 12 months, and the need for invasive mechanical ventilation (IMV) or continuous renal replacement therapy (CRRT) during the ICU stay. Functional outcome was assessed by the Glasgow Outcome Scale Extended (GOSE, range 1-8, with < 5 representing an unfavourable outcome). Associations between plasma calprotectin and outcomes were examined in binary logistic regression analyses adjusted for age, sex, BMI, hypertension, smoking, and creatinine.

RESULTS

High plasma calprotectin on admission and day 7 was independently associated with increased 12-month mortality. Increasing calprotectin from admission to day 7 was independently associated with higher mortality at 12 months [OR 2.10 (95% CI 1.18-3.74), p = 0.012], unfavourable functional outcome at 3 months [OR 2.53 (95% CI 1.07-6.10), p = 0.036], and the use of IMV [OR 2.23 (95% CI 1.10-4.53), p = 0.027)] and CRRT [OR 2.07 (95% CI 1.07-4.00), p = 0.031)]. A receiver operator characteristic (ROC) model including day 7 calprotectin and age was a good predictor of 12-month mortality [AUC 0.79 (95% CI 0.74-0.84), p < 0.001]. Day 7 calprotectin alone predicted an unfavourable functional outcome at 3 months [AUC 0.67 (95% CI 0.58-0.76), p < 0.001].

CONCLUSION

In critically ill COVID-19 patients, increasing calprotectin levels after admission to the ICU are associated with 12-month mortality and unfavourable functional outcome in survivors. Monitoring plasma calprotectin dynamics in the ICU may be considered to evaluate prognosis in critical COVID-19.

STUDY REGISTRATION

ClinicalTrials.gov Identifier: NCT04974775, registered April 28, 2020.

Calprotectin: two sides of the same coin

Calprotectin (CLP) is a calcium-binding protein produced by neutrophils and monocytes in the course of inflammation. Today, the role of faecal CLP in chronic IBD is well known, but in recent years attention has shifted towards circulating CLP. In fact, this molecule can be measured in different biological fluids: blood, saliva and urine, using different analytic methods that are described in this review. Furthermore, different data confirm the relevant role of serum CLP in autoimmune diseases. In this review we will highlight the correlation between high levels of circulating CLP and specific autoantibodies of major autoimmune pathologies paving the way to the employment of CLP measurement as useful biomarker for monitoring outcome in different pathologies.

Serum Biomarkers in Diagnosis and Clinical Management of Inflammatory Bowel Disease: Anything New on the Horizon?

Persistent inflammation in inflammatory bowel disease (IBD) leads to progressive damage to the gastrointestinal tract, resulting in potentially severe sequelae. Diagnosis primarily relies on invasive endoscopy and monitoring of faecal calprotectin (FC), which has limitations, particularly regarding patient compliance. There is a pressing need for a new biomarker that is non-invasive, easily determinable, and possesses good diagnostic accuracy for both dia-gnosing and monitoring IBD. Our narrative review covers the latest developments in novel serum biomarkers, focusing on those with promising diagnostic accuracy and laboratory methods, and evaluates them in the context of established biomarkers such as FC and CRP. Serum calprotectin (SC) and leucine-rich alpha-2 glycoprotein (LRG) show the most extensive evidence and relatively good diagnostic accuracy but currently cannot replace FC due to insufficient evidence. Major limitations of the analysed studies include their monocentric nature, small sample sizes, lack of longitudinal monitoring and in some cases, missing assessments of endoscopic activity. ELISA holds a leading position among the laboratory methods; however, emerging evidence supports the potential use of point-of-care testing (POCT). Establishing these biomarkers for regular clinical application will require further validation through multicentric studies involving a larger number of patients with a longitudinal design, concurrent assessment of endoscopic activity and pro-active monitoring of the biomarker. However, based on the evidence accumulated so far, SC might potentially serve as a complementary biomarker and/or in assessing the activity of extraintestinal manifestations in IBD patients, while LRG appears to be effective in evaluating endoscopic activity, especially in small bowel CD.

Calprotectin in Patients with Rheumatic Immunomediated Adverse Effects Induced by Checkpoints Inhibitors

BACKGROUND

this is an exploratory study to evaluate calprotectin serum levels in patients with rheumatic immune-related adverse events (irAEs) induced by immune checkpoint inhibitor (ICI) treatment.

METHODS

this is a retrospective observational study including patients with irAEs rheumatic syndromes. We compared the calprotectin levels to those in a control group of patients with RA and with a control group of healthy individuals. Additionally, we included a control group of patients treated with ICI but without irAEs to check calprotectin levels. We also analysed the performance of calprotectin for the identification of active rheumatic disease using receiver operating characteristic curves (ROC).

RESULTS

18 patients with rheumatic irAEs were compared to a control group of 128 RA patients and another group of 29 healthy donors. The mean calprotectin level in the irAE group was 5.15 μg/mL, which was higher than the levels in both the RA group (3.19 μg/mL) and the healthy group (3.81 μg/mL) (cut-off 2 μg/mL). Additionally, 8 oncology patients without irAEs were included. In this group, calprotectin levels were similar to those of the healthy controls. In patients with active inflammation, the calprotectin levels in the irAE group were significantly higher (8.43 μg/mL) compared to the RA group (3.94 μg/mL). ROC curve analysis showed that calprotectin had a very good discriminatory capacity to identify inflammatory activity in patients with rheumatic irAEs (AUC of 0.864).

CONCLUSIONS

the results suggest that calprotectin may serve as a marker of inflammatory activity in patients with rheumatic irAEs induced by treatment with ICIs.

Changes in Calprotectin (S100A8-A9) and Aldolase in the Saliva of Horses with Equine Gastric Ulcer Syndrome

Equine gastric ulcer syndrome (EGUS) is a highly prevalent disease that affects horses worldwide. Within EGUS, two different forms have been described: equine squamous gastric disease (ESGD) and equine glandular gastric disease (EGGD). The associated clinical signs cause detrimental activity performance, reducing the quality of life of animals. Saliva can contain biomarkers for EGUS that could be potentially used as a complementary tool for diagnosis. The objective of this work was to evaluate the measurements of calprotectin (CALP) and aldolase in the saliva of horses as potential biomarkers of EGUS. For this purpose, automated assays for the quantification of these two proteins were analytically validated and applied for detecting EGUS in a total of 131 horses divided into 5 groups: healthy horses, ESGD, EGGD, combined ESGD and EGGD, and horses with other intestinal pathologies. The assays showed good precision and accuracy in analytical validation, and they were able to discriminate between horses with EGUS and healthy horses, especially in the case of CALP, although they did not show significant differences between horses with EGUS and horses with other diseases. In conclusion, salivary CALP and aldolase can be determined in the saliva of horses and further studies are warranted to elucidate the potential of these analytes as biomarkers in EGUS.

Analytical and clinical evaluation of DiaSorin Liaison® Calprotectin fecal assay adapted for serum samples

Background

Calprotectin is a calcium‐binding protein that can be measured in serum, plasma, and feces. Increased serum and plasma calprotectin concentrations have been found in chronic inflammatory rheumatic disorders. An analytical and clinical evaluation of the DiaSorin Liaison® fecal Calprotectin assay using LIAISON® XL was performed.

Methods

The protocol included an analytical and clinical evaluation in which imprecision, the linearity of dilution, differences between serum and plasma samples and method comparison with CalproLab™ ELISA kit were assessed. Serum calprotectin concentrations in active (n = 26) and remission (n = 23) rheumatoid arthritis (RA) patients were compared.

Results

The intra‐day and inter‐day analytical imprecision CVs ranged from 2.9% to 4.0% and 2.7% to 10.4%, respectively. Correlation between measured and expected values was high (R > 0.99), indicating good linearity. The Wilcoxon signed‐rank test showed that serum and plasma matched samples presented statistically significant differences (p < 0.001) being the highest concentrations of calprotectin observed in serum samples. Deming regression equation was as follows: Diasorin calprotectin (μg/ml) = −0.32 (95% CI: −0.65 ‐ −0.05) +1.58 (95% CI: 1.42–1.79).* Calprolab calprotectin (μg/ml). Significantly higher serum calprotectin levels were found in RA patients with active disease when compared to patients with low disease activity or in clinical remission (mean ± SD) [(3.35 μg/ml ± 1.55) vs. (1.63 μg/ml ± 0.52), p < 0.001] and these levels correlated well with all disease activity indices.

Conclusions

The DiaSorin Liaison® fecal Calprotectin assay adapted for serum samples showed adequate technical performances and the clinical performances were similar to other assays.

Circulating levels of calprotectin, a signature of neutrophil activation in prediction of severe respiratory failure in COVID-19 patients: a multicenter, prospective study (CalCov study)

OBJECTIVE

Severe COVID-19 is characterized by a dysregulated immune response in which neutrophils play a critical role. Calprotectin reflects neutrophil activation and is involved in the self-amplifying thrombo-inflammatory storm in severe COVID-19. We aimed to evaluate the role of calprotectin in early prediction of severity in COVID-19 patients.

METHODS

This was a multicenter prospective observational study enrolling consecutive adult COVID-19 patients. On arrival to emergency department, blood samples were collected for laboratory tests, including serum calprotectin. The primary outcome was severe respiratory failure requiring invasive mechanical ventilation and the secondary outcome was need for Intensive Care Unit (ICU) admission.

RESULTS

Study population included 395 patients, 57 (14.4%) required invasive mechanical ventilation and 100 (25.3%) were admitted to ICU. Median serum calprotectin levels were significantly higher in intubated (3.73 mg/L vs. 2.63 mg/L; p < 0.001) and ICU patients (3.48 mg/L vs. 2.60 mg/L; p = 0.001). Calprotectin showed a significant accuracy to predict the need for invasive mechanical ventilation (ROC AUC 0.723) and ICU admission (ROC AUC 0.650). In multivariate analysis, serum calprotectin was an independent predictor of invasive mechanical ventilation (OR 1.161) and ICU admission (OR 1.068).

CONCLUSION

Serum calprotectin can be used as an early predictor of severity in COVID-19 patients.

Second Trimester Maternal Leptin Levels Are Associated with Body Mass Index and Gestational Weight Gain but not Birth Weight of the Infant

INTRODUCTION

Obesity is increasing among the pregnant population. Leptin has an important role in the regulation of energy balance and hunger. The aim of this study was to investigate the association between maternal leptin levels with maternal obesity, gestational weight gain (GWG), single nucleotide polymorphisms (SNPs) within the leptin gene, and the age-adjusted birth weight of the child.

MATERIAL AND METHODS

Maternal leptin levels (n = 740) and SNPs (n = 504) were analyzed in blood samples taken within the Uppsala Biobank of Pregnant women at pregnancy weeks 16-19.

RESULTS

Maternal leptin levels differed significantly between body mass index (BMI) groups. Normal weight women had the lowest median leptin levels and levels increased with each BMI group. Leptin SNP genotype was not associated with leptin levels or BMI. There was also no association between maternal leptin levels and age-adjusted birth weight of the child except for a negative association between leptin levels and birth weight in the morbid obese group.

DISCUSSION/CONCLUSION

Maternal BMI was identified as the best positive explanatory factor for maternal leptin levels. Leptin was a strong positive explanatory factor for GWG. Birth weight of children of uncomplicated pregnancies was, however, dependent on maternal height, BMI, GWG, and parity but not leptin levels, except for in morbid obese women where a negative association between maternal leptin levels and birth weight was found. We speculate that this indicates altered placental function, not manifested in pregnancy complication. We conclude that maternal leptin levels do not affect the birth weight of the child more than BMI, GWG, and parity.

Calprotectin (S100A8/S100A9)-induced cytotoxicity and apoptosis in human gastric cancer AGS cells: Alteration in expression levels of Bax, Bcl-2, and ERK2

Calprotectin is a heterodimeric EF-hand Ca²⁺ binding protein that is typically released by infiltrating polymorphonuclear leukocytes and macrophages. This protein is a key player linking inflammation and cancer. Due to the increased levels of calprotectin in different inflammatory diseases and cancer, it is considered as a marker for diagnostic purposes. In this study, we evaluated the mechanism of cell viability and apoptotic-inducing effects of recombinant human calprotectin (rhS100A8/S100A9) on the gastric adenocarcinoma (AGS), the most common type of gastric cancer cell line. AGS cells were exposed to the different concentrations (5-100 μg/ml) of calprotectin for 24, 48, and 72 h, and cell viability was assessed through 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptotic-inducing effects of calprotectin were evaluated by sub-G1 cell cycle assay and Annexin V/propidium iodide double staining. Furthermore, real-time polymerase chain reaction and Western blot analysis were performed to evaluate the mechanism of action of calprotectin. Our findings indicated that calprotectin inhibits growth and viability of AGS cells in a time- and dose-dependent manner. The half-maximal inhibitory concentration values were measured as 85.77, 79.14, and 65.39 μg/ml for 24, 48, and 72 h, respectively. Additionally, we found that calprotectin downregulated the expression of antiapoptotic protein Bcl-2 and upregulated proapoptotic protein Bax in a time- and concentration-dependent fashion. Calprotectin also slightly upregulated the expression of extracellular signal-regulated protein kinase 2 (ERK2), while it significantly decreased the levels of phospho-ERK in a time-dependent manner. Overall, these findings indicated that calprotectin has cytotoxicity and apoptosis-inducing effects on AGS cell lines in high concentration by modulating Bax/Bcl-2 expression ratio accompanied by inhibition of ERK activation.

Polycystic Ovary Syndrome and Insulin Physiology: An Observational Quantitative Serum Proteomics Study in Adolescent, Normal-Weight Females

BACKGROUND

Polycystic ovary syndrome (PCOS) is a common endocrine disorder associated with insulin resistance, even in the absence of overweight/obesity. The aim of the present study is to examine the global serum proteomic profile of adolescent, normal-weight females with PCOS in order to gain novel insight in the association of this endocrine disorder with insulin physiology and to identify novel circulating markers that can guide intervention protocols.

METHODS

Non-depleted serum from normal-weight (BMI: 18-23 kg m^-2 ), adolescent females (13-21 years old) with PCOS (n = 20) is compared to BMI- and age-matched healthy controls (n = 20) using our 3D quantitative proteomics methodology. Serum samples from study participants are randomly pooled to form four biological replicates of females with PCOS and four of healthy controls (n = 5 per sample pool).

RESULTS

One-hundred and twenty-six proteins are differentially expressed in females with PCOS compared to controls. Gene ontology analysis shows significant enrichment for terms related to inflammatory immune response, metabolism and insulin-like growth factor receptor signaling pathway. Circulating levels of IGF-1 and -2 and IGFBP-2, -3, and -4 are found to be lower in females with PCOS compared to healthy controls.

CONCLUSIONS

The present serum proteomics study provides insight into the pro-inflammatory status and insulin dysregulation in young females with PCOS and identifies potential serological markers that can guide early intervention protocols.

Measuring calprotectin in plasma and blood with a fully automated turbidimetric assay

Calprotectin in plasma and blood might prove to be a useful biomarker of inflammation and infection; however, automated methods for analysing the concentration of calprotectin in those materials are lacking. We have validated a fully automated turbidimetric method and present health-related reference limits. Calprotectin was measured by Siemens Advia XPT with the Bühlmann fCAL® turbo test (Bühlmann Laboratories AG, Schönenbuch, Switzerland), a particle enhanced turbidimetric immunoassay for quantification of calprotectin in fecal extracts. Plasma and serum samples were analysed directly, while whole blood was first extracted with M-PER® Mammalian Protein Extraction Reagent (ThermoFisher) and diluted with B-CAL-EX (Bühlmann). We studied analytical imprecision, estimated health-related reference limits and examined the correlation between neutrophil-calprotectin (blood-calprotectin adjusted for plasma-calprotectin) and the neutrophil count. The intermediate ('day-to-day') coefficient of variation was 3.5 and 1.0% for heparin-plasma-calprotectin at 0.52 mg/L and 3.53 mg/L, respectively, and 4.9% for heparin-blood-calprotectin at 50.2 mg/L. Health-related reference limits were 0.470-3.02 mg/L for calprotectin in heparin-plasma, 50.8-182 mg/L for calprotectin in heparin-blood, 0.534-2.41% for the ratio between them and 24.7-33.3 pg for the mean amount of calprotectin per neutrophil. Compared to heparin-plasma, calprotectin concentrations were significantly lower in EDTA-plasma and higher in serum (p < .05). Correlation between neutrophil-calprotectin and the neutrophil count was excellent. We have shown that the Bühlmann fCAL® turbo test can be used to measure calprotectin in plasma and blood.

Calprotectin (S100A8/S100A9): a key protein between inflammation and cancer

BACKGROUND

Calprotectin (S100A8/S100A9), a heterodimeric EF-hand Ca²⁺ binding protein, are abundant in cytosol of neutrophils and are involved in inflammatory processes and several cancerous pathogens.

OBJECTIVE

The purpose of the present systematic review is to evaluate the pro- and anti-tumorigenic functions of calprotectin and its relation to inflammation.

MATERIALS AND METHODS

We conducted a review of studies published in the Medline (1966-2018), Scopus (2004-2018), ClinicalTrials.gov (2008-2018) and Google Scholar (2004-2018) databases, combined with studies found in the reference lists of the included studies.

RESULTS

Elevated levels of S100A8/S100A9 were detected in inflammation, neoplastic tumor cells and various human cancers. Recent data have explained that many cancers arise from sites of infection, chronic irritation, and inflammation. The inflammatory microenvironment which largely includes calprotectin, has an essential role on high producing of inflammatory factors and then on neoplastic process and metastasis.

CONCLUSION

Scientists have shown different outcomes in inflammation, malignancy and apoptosis whether the source of the aforementioned protein is extracellular or intracellular. These findings are offering new insights that anti-inflammatory therapeutic agents and anti-tumorigenic functions of calprotectin can lead to control cancer development.

Extraction, isolation, and concentration of calprotectin antigen (S100A8/S100A9) from granulocytes

BACKGROUND

Calprotectin is a promising biomarker for granulocyte activation. It is mainly measured in faeces as a marker for inflammatory bowel disease. A limitation is that there is no widely accepted calibrator.

AIM

To establish a method for purification of calprotectin from human granulocytes that is easily reproducible, reliable, and could contribute to a better agreement between different calprotectin methods.

METHODS AND RESULTS

Calprotectin was purified from granulocyte extracts using ion-exchange chromatography. The granulocytes were separated from blood bags. The purity was analysed by analysing pixel density of a picture of the sodium dodecyl sulfate polyacrylamide gel electrophoresis and by size exclusion chromatography. The calprotectin concentration of the pure antigen solution was determined using Biuret method. The purity was >95% for 3 preparations, and their concentrations were 1079, 1080, and 1813 mg/L.

CONCLUSION

It is possible to reproducibly prepare highly purified calprotectin antigen from human granulocytes. The preparations can be used for preparing calibrators, controls for immunological calprotectin assays, and immunisation for raising antibodies against human calprotectin in hens.

Performance of plasma calprotectin as a biomarker of early sepsis: a pilot study

AIM

To determine the performance of plasma calprotectin as a marker of sepsis on intensive care unit (ICU) admission and as a marker of mortality day 30 post-ICU admission.

MATERIALS & METHODS

Consecutive ICU patients were allocated to: sepsis (n = 15), postoperative inflammation (n = 23) and intoxication without inflammation (n = 7) groups.

RESULTS

Calprotectin was 4.3 (2.6-8.2; mg/l; median [interquartile range]) in the sepsis, 2.8 (1.6-4.4) in the postoperative and 0.7 (0.4-1.6) in the intoxication groups. Area under the receiver operating characteristic curve for sepsis versus intoxication group was: 0.95, for sepsis versus postoperative groups: 0.65 and for survivors versus nonsurvivors: 0.70.

CONCLUSION

Calprotectin was a sensitive marker of systemic inflammation, is a potential sepsis marker and performed well as mortality predictor in this pilot study.