Circulating calprotectin as biomarker in neutrophil-related inflammation: Pre-analytical recommendations and reference values according to sample type

Circulating calprotectin as a potential biomarker of persistent olfactory dysfunctions in Post-COVID-19 patients

BACKGROUND

This longitudinal prospective study aims to investigate the potential of circulating calprotectin (cCLP) as a biomarker in persistent olfactory dysfunctions following COVID-19 infection.

METHODS

Thirty-six patients with persistent hyposmia or anosmia post COVID-19 were enrolled (HT0) and re-evaluated after three months of olfactory training (HT1). Two control groups included 18 subjects without olfactory defects post COVID-19 (CG1) and 18 healthy individuals (CG2). Nasal brushing of the olfactory cleft and blood collection were performed to assess circulating calprotectin levels.

RESULTS

Higher calprotectin levels were observed in serum and nasal supernatant of hyposmic patients (HT0) compared to control groups (CG1 and CG2). Post-olfactory training (HT1), olfactory function improved significantly, paralleled by decreased calprotectin levels in serum and nasal samples. Circulating calprotectin holds potential as a biomarker in persistent olfactory dysfunctions after COVID-19. The decrease in calprotectin levels post-olfactory training implies a role in monitoring and evaluating treatment responses.

DISCUSSION AND CONCLUSIONS

These findings contribute to the growing literature on potential biomarkers in post-COVID-19 olfactory dysfunctions and underscore the importance of investigating novel biomarkers for personalized patient management. Nevertheless, further studies are needed to validate the application of calprotectin assay in nasal diseases and its correlation with nasal cytology.

Assessment of immunopathological responses of a novel non-chemical biocide in C57BL/6 for safe disinfection usage

BACKGROUND

Water electrospray technology has been developed and extensively studied for its physical properties and potential application as a non-chemical biocide against airborne pathogens. However, there are still concerns regarding the safety and potential toxicity of inhaling water electrospray (WE) particles. To address these potential hazards and offer insights into the impact of WE on humans, we analyzed the immunopathological response to WE by employing an intranasal challenge C57BL/6 mouse model. This analysis aimed to compare the effects of WE with those of sodium hypochlorite (SH), a well-known biocidal agent.

RESULTS

The study findings suggest that the WE did not trigger any pathological immune reactions in the intranasal-challenged C57BL/6 mouse model. Mice challenged with WE did not experience body weight loss, and there was no increase in inflammatory cytokine production compared to SH-treated mice. Histopathological analysis revealed that WE did not cause any damage to the lung tissue. In contrast, mice treated with SH exhibited significant lung tissue damage, characterized by the infiltration of neutrophils and eosinophils. Transcriptomic analysis of lung tissue further confirmed the absence of a pathological immune response in mice treated with WE compared to those treated with SH. Upon intranasal challenge with WE, the C57BL/6 mouse model did not show any evidence of immunopathological damage.

CONCLUSIONS

The results of this study suggest that WE is a safe technology for disinfecting airborne pathogens. It demonstrated little to no effect on immune system activation and pathological outcomes in the intranasal challenge C57BL/6 mouse model. These findings not only support the potential use of WE as an effective and safe method for air disinfection but also highlight the value of the intranasal challenge of the C57BL/6 mouse model in providing significant immunopathological insights for assessing the inhalation of novel materials for potential use.

Diagnostic accuracy of serum calprotectin measured by CLIA and EIA in juvenile idiopathic arthritis: a proof-of-concept study

Objective

C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are used to assess disease activity in juvenile idiopathic arthritis (JIA). However, because these biomarkers do not always differentiate between active and inactive disease, there is a need for alternative markers such as serum calprotectin (sCal). The main aim of this proof-of-concept study was to assess the diagnostic accuracy of sCal in patients with JIA. Secondary aims were to identify the optimal sCal cut-off levels to define active disease and evaluate the association between these biomarkers and disease activity status.

Methods

Serum samples were obtained from 25 pediatric patients with JIA. Serum calprotectin levels were determined by two different assays, the QUANTA FLASH chemiluminescence immunoassay (CLIA) from Inova Diagnostics and the solid-phase enzyme immunoassay (EIA) from Bühlmann Laboratories. Diagnostic accuracy was assessed for sCal CLIA, sCal EIA, CRP, and ESR. The results obtained by the CLIA and EIA methodologies were compared. We also evaluated the association between the individual each biomarkers (sCal CLIA, sCal EIA, CRP, and ESR) and disease activity (according to JADAS-27 criteria and the ACR criteria modified by Anink and colleagues).

Results

For both sCal assays (CLIA and EIA), the optimal cut-off level (ROC analysis) was the same (2.3 µg/ml). Serum calprotectin levels measured by CLIA and EIA were strongly correlated with each other (Kendall's tau-b, 0.71; p < 0.001). Compared to ESR and CRP, sCal CLIA and EIA were both more accurate (i.e., greater sensitivity) in identifying patients with active disease. By contrast, ESR and CRP were more effective in identifying patients in remission (i.e., better specificity).

Conclusion

This proof-of-concept study shows that determination of serum calprotectin levels with CLIA or EIA can accurately identify the presence of active disease in patients with JIA.

Mortality prediction model from combined serial lactate, procalcitonin and calprotectin levels in critically ill patients with sepsis: A retrospective study according to Sepsis-3 definition

OBJECTIVE

1) To evaluate the ability of baseline and on 24 h serum calprotectin, in comparison to canonical biomarkers (lactate and procalcitonin), for prognosis of 28-day mortality in critically ill septic patients; and 2) To develop a predictive model combining the three biomarkers.

DESIGN

A single-center, retrospective study.

SETTING

Intensive Care Unit of a university hospital.

PATIENTS OR PARTICIPANTS

One hundred and seventy three septic pacientes were included.

INTERVENTIONS

Measurement of baseline lactate, procalcitonin and calprotectin level and procalcitonin and calprotectin levels on 24 h.

MAIN VARIABLES OF INTEREST

Demographics and comorbidities, SOFA score on ICU admission, baseline lactate, procalcitonin and calprotectin on admission and on 24 h and 28-day mortality.

RESULTS

1) On ICU admission, lactate was the only biomarker achieving a significant accuracy (AUC: 0.698); 2) On 24 h, no differences were found on procalcitonin and calprotectin levels. Procalcitonin and calprotectin clearances were significantly lower in non-survivors and both achieved a moderate performance (AUCs: 0.668 and 0.664, respectively); 3) A biomarker based-model achieved a significant accuracy (AUC: 0.766), trending to increase (AUC: 0.829) to SOFA score alone; y 4) Baseline lactate levels and procalcitonin and calprotectin clearance were independent predictors for the outcome.

CONCLUSIONS

1) Baseline and on 24 h calprotectina and procalcitonin levels lacked ability in predicting 28-day mortality; 2) Accuracy of clearance of both biomarkers was moderate; and 3) Combination of SOFA score and the predictive biomarker based-model showed a high prognostic accuracy.

A Prospective Study of the Association Between Plasma Calprotectin Levels and New-Onset CKD in the General Population

Introduction

Systemic inflammation has been associated with chronic kidney disease (CKD). In this study, we aimed to investigate a potential association between the plasma biomarker of inflammation calprotectin and new-onset CKD in a population-based cohort study.

Methods

Individuals without CKD at baseline (n = 4662) who participated in the Prevention of REnal and Vascular ENd-stage Disease (PREVEND) prospective population-based cohort study in the Netherlands were included. Baseline plasma calprotectin levels were assessed in samples that had been stored at -80 °C. Occurrence of new-onset CKD was defined as a composite outcome of an estimated glomerular filtration rate (eGFR) <60 ml/min per 1.73 m2, urinary albumin excretion (UAE) >30 mg/24h, or both.

Results

Baseline median (interquartile range) plasma calprotectin levels were 0.49 (0.35-0.68) mg/l and baseline median eGFR was 95.9 (interquartile range: 85.0-105.7) ml/min per 1.73 m2. After median follow-up of 8.3 (7.8-8.9) years, 467 participants developed new-onset CKD. Baseline plasma calprotectin levels were significantly associated with an increased risk of new-onset CKD (hazard ratio [HR] per doubling 1.28 [95% confidence interval, CI: 1.14-1.44], P < 0.001), independent of potentially confounding factors (HR 1.14 [95% CI: 1.01-1.29], P = 0.034), except for baseline high-sensitive C-reactive protein (hs-CRP) (HR 1.05 [0.91-1.21], P = 0.494). In secondary analyses, the association between plasma calprotectin and occurrence of UAE >30 mg/24h remained significant (HR 1.17 [1.02-1.34], P = 0.027), but not significantly so for the incidence of eGFR <60 ml/min per 1.73 m2 as individual outcome (HR 1.15 [0.92-1.43], P = 0.218).

Conclusion

Higher plasma calprotectin levels are associated with an increased risk of developing CKD in the general population. This association is mitigated after adjustment for hs-CRP, and more pronounced with new-onset CKD defined by UAE.

Establishing a pediatric reference interval for plasma calprotectin

Plasma calprotectin is a promising new biomarker of inflammatory activity and has been found to correlate well with clinical and endoscopic activity in children and adolescents with inflammatory bowel disease. A pediatric reference interval for plasma calprotectin has not been established for the Phadia 250 EliA™ Calprotectin fluoroenzyme immunoassay. In studies regarding pre-analytical properties, excellent precision and stability was found. However, sensitivity to hemolysis was demonstrated. We identified pediatric blood samples from apparently healthy children who were referred by their general practitioner for blood sampling including measurement of hemoglobin (Hb) and C-reactive protein (CRP). We excluded samples from children who had undergone additional blood sampling within 2 months before or after the index sample, if Hb was outside of local reference ranges or CRP levels were above the lower limit of the measuring interval (LLM), and any samples with a hemolysis above 0.02 mmol/L. Using this algorithm, we identified 141 blood samples. No outliers were identified. We established the following reference intervals according to CLSI C28-A3 using non-parametric statistics: 1-17 years: 16-246 µg/L. Our results may prove useful for further utilization of plasma calprotectin as a marker of inflammation in children and adolescents with inflammatory disorders.

Assessment of the predictive value of plasma calprotectin in the evolution of SARS-Cov-2 primo-infection

BACKGROUND

The COVID-19 epidemic still calls for anticipation aimed at preventing the overloading of critical care services. With this in mind, the predictive value of easily accessible biomarkers is to be assessed.

OBJECTIVE

Secretion of calprotectin is stimulated during an inflammatory process, especially in the cytokine storm. We tried to determine whether early plasma concentration of calprotectin in patients with primary SARS-CoV-2 infection could predict an adverse outcome in cases of COVID-19.

METHODS

We included 308 patients with a primary diagnosis of SARS-CoV-2 confirmed by PCR. Heparinized tube samples, collected within the first 24 h of hospitalization, were used for biomarker assays, in which plasma calprotectin was included. Data from the patients' medical records and severity groups established subsequent to diagnosis at the end of hospitalization were collected.

RESULTS

Early plasma calprotectin concentration is significantly associated with progression to a severe form of COVID-19 in patients with primary infection (Relative Risk: 2.2 [1.6-2.7]). In multivariate analysis, however, it does not appear to provide additional information compared to other parameters (age, GFR, CRP…).

CONCLUSION

Our study shows that while an early single blood test for calprotectin could help to predict the progression of a primary SARS-CoV-2 infection, it is not superior to the other parameters currently used in emergency medicine. However, it paves the way for future considerations, such as the interest of this biomarker for high-risk infected patients (immunocompromised individuals…). Finally, the usefulness of early serial measurements of plasma calprotectin to assess progression towards severity of COVID-19 requires further assessment.

Pre-treatment calprotectin (MRP8/14) provides no added value to testing CRP alone in terms of predicting response to TNF inhibitors in rheumatoid arthritis in a post hoc analysis

OBJECTIVES

The inflammatory protein calprotectin (MRP8/14) has been identified as a promising biomarker of treatment response in rheumatoid arthritis (RA). Our aim was to test MRP8/14 as a biomarker of response to tumour necrosis factor (TNF)-inhibitors in the largest RA cohort to date and to compare with C-reactive protein (CRP).

METHODS

Serum MRP8/14 was measured in 470 patients with RA about to commence treatment with adalimumab (n=196) or etanercept (n=274). Additionally, MRP8/14 was measured in the 3-month sera of 179 adalimumab-treated patients. Response was determined using European League against Rheumatism (EULAR) response criteria calculated using the traditional 4-component (4C) DAS28-CRP and alternate validated versions using 3-component (3C) and 2-component (2C), clinical disease activity index (CDAI) improvement criteria and change in individual outcome measures. Logistic/linear regression models were fitted for response outcome.

RESULTS

In the 3C and 2C models, patients with RA were 1.92 (CI: 1.04 to 3.54) and 2.03 (CI: 1.09 to 3.78) times more likely to be classified as EULAR responders if they had high (75th quartile) pre-treatment levels of MRP8/14 compared with low (25th quartile). No significant associations were observed for the 4C model. When only using CRP as a predictor, in the 3C and 2C analyses, patients above the 75th quartile were 3.79 (CI: 1.81 to 7.93) and 3.58 (CI: 1.74 to 7.35) times more likely to be EULAR responders and addition of MRP8/14 did not significantly improve model fit (p values=0.62 and 0.80, respectively). No significant associations were observed in the 4C analysis. Exclusion of CRP from the outcome measure (CDAI) did not result in any significant associations with MRP8/14 (OR 1.00 (CI: 0.99 to 1.01), suggesting that the associations were due to the correlation with CRP and that there is no additional utility of MRP8/14 beyond use of CRP in patients with RA starting TNFi therapy.

CONCLUSION

Beyond correlation with CRP, we found no evidence to suggest that MRP8/14 explains additional variability in response to TNFi in patients with RA over and above CRP alone.

Serial measurement of circulating calprotectin as a prognostic biomarker in COVID-19 patients in intensive care setting

OBJECTIVES

Circulating calprotectin (cCLP) has been shown to be a promising prognostic marker for COVID-19 severity. We aimed to investigate the prognostic value of serial measurements of cCLP in COVID-19 patients admitted to an intensive care unit (ICU).

METHODS

From November 2020 to May 2021, patients with COVID-19, admitted at the ICU of the OLV Hospital, Aalst, Belgium, were prospectively included. For sixty-six (66) patients, blood samples were collected at admission and subsequently every 48 h during ICU stay. On every sample (total n=301), a cCLP (EliA™ Calprotectin 2, Phadia 200, Thermo Fisher Scientific; serum/plasma protocol (for Research Use Only, -RUO-) and C-reactive protein (CRP; cobas c501/c503, Roche Diagnostics) analysis were performed. Linear mixed models were used to associate biomarkers levels with mortality, need for mechanical ventilation, length of stay at ICU (LOS-ICU) and medication use (antibiotics, corticosteroids, antiviral and immune suppressant/modulatory drugs).

RESULTS

Longitudinally higher levels of all biomarkers were associated with LOS-ICU and with the need for mechanical ventilation. Medication use and LOS-ICU were not associated with variations in cCLP and CRP levels. cCLP levels increased significantly during ICU hospitalization in the deceased group (n=21/66) but decreased in the non-deceased group (n=45/66). In contrast, CRP levels decreased non-significantly in both patient groups, although significantly longitudinally higher CRP levels were obtained in the deceased subgroup.

CONCLUSIONS

Serial measurements of cCLP provides prognostic information which can be useful to guide clinical management of COVID-19 patients in ICU setting.

Serum Calprotectin as a Promising Inflammatory Biomarker in Psoriatic Arthritis: a 1-Year Longitudinal Study

INTRODUCTION

There are few biomarkers correlated with psoriatic arthritis (PsA). We aimed to explore the clinical value of calprotectin (CLP) in PsA in disease activity and treatment targets.

METHODS

Serum CLP was detected by enzyme-linked immunosorbent assay (ELISA) in 71 patients with PsA, 55 patients with psoriasis (PsO), and 10 healthy controls. The association of serum CLP with disease activity index at baseline and follow-up was analyzed. Cox regression and receiver operating characteristic (ROC) analysis were used to evaluate the potential of CLP for predicting the achievement of treatment targets, including low disease activity (LDA), remission, and minimal disease activity (MDA).

RESULTS

Serum CLP levels (μg/ml) were significantly increased in patients with PsA/PsO compared with healthy controls (p < 0.001). Serum CLP levels were positively associated with psoriasis area and severity index (PASI), disease activity in psoriatic arthritis (DAPSA), and its components [including tender joint count (TJC), swollen joint count (SJC), patient's global assessment (PGA), and visual analog scale (VAS)-pain, r 0.290-0.601, all p value < 0.05]. After 1-year follow-up, the number of patients with PsA in remission and MDA increased [17 (23.9%) versus 47 (66.1%) and 21 (29.5%) versus 52 (73.2%) respectively, all p value < 0.001]. Cox regression and Kaplan-Meier survival analysis indicated that patients with lower CLP obtain LDA, MDA, and remission earlier, including remission and MDA within a year (all p-value < 0.05). ROC analysis showed the ability of serum at baseline to predict the achievement of the treatment target in 3 months [area under the curve (AUC) 0.663-0.691, all p-values < 0.05].

CONCLUSIONS

Serum CLP level was correlated with disease activity in PsA. It also possessed the ability to predict the achievement of the therapeutic target. These features of CLP would make it a useful tool in clinical work.

Is canine calprotectin in serum stabile after storage at low temperature?

BACKGROUND

In human and veterinary medicine calprotectin is most widely used in diagnosing different gastro-intestinal diseases. The aim of this study was to assess the stability of canine calprotectin (cCP) in serum after storage at low temperatures and imprecision of the method.

METHODS

Blood samples were collected from dogs with different clinical diagnoses. Twenty-two dogs were included in this study. Calprotectin concentration was measured 4 hours after serum separation (T0), and after being frozen at - 80 °C for 8 (T1) and 16 weeks (T2). The maximum permissible difference (MPD) was derived from the equation for calculating total error (TE) TE = %Bias + (1.96 x %CV), where bias and coefficient of variation (CV) were defined by the manufacturer. The dogs enrolled in this study were patients admitted during the morning (9-12 a.m.), on the day the first measurement was performed. All sample analysis for determination of stability were done in duplicates. For determination of within-run precision, the two patients' serum samples were analyzed in 20 replicates. Imprecision was assessed by analyzing 20 replicates on one plate on two samples where high and low concentrations were anticipated.

RESULTS

The calculated value of MPD was 32.52%. Median calprotectin concentrations were higher at T1 114.08 μg/L (IQR = 55.05-254.56) and T2 133.6 μg/L (IQR = 100.57-332.98) than at T0 83.60 μg/L (IQR = 50.38-176.07). Relative and absolute bias at T1 (49.3%; 45.98 μg/L) and T2 (109.93%; 94.09 μg /L) have shown that calprotectin concentrations increase after long term storage at - 80 °C.

CONCLUSION

The results of the present study indicate that c-CP was not stable for 16 weeks at low storage temperature (- 80 °C). Considering the observed change in the concentration of c-CP at T1, a storage time of 8 weeks should be safely applied. The method imprecision was not satisfactory, especially in the lower concentration range.

Biomarkers in Systemic Juvenile Idiopathic Arthritis, Macrophage Activation Syndrome and Their Importance in COVID Era

Systemic juvenile idiopathic arthritis (sJIA) and its complication, macrophage activation syndrome (sJIA-MAS), are rare but sometimes very serious or even critical diseases of childhood that can occasionally be characterized by nonspecific clinical signs and symptoms at onset-such as non-remitting high fever, headache, rash, or arthralgia-and are biologically accompanied by an increase in acute-phase reactants. For a correct positive diagnosis, it is necessary to rule out bacterial or viral infections, neoplasia, and other immune-mediated inflammatory diseases. Delays in diagnosis will result in late initiation of targeted therapy. A set of biomarkers is useful to distinguish sJIA or sJIA-MAS from similar clinical entities, especially when arthritis is absent. Biomarkers should be accessible to many patients, with convenient production and acquisition prices for pediatric medical laboratories, as well as being easy to determine, having high sensitivity and specificity, and correlating with pathophysiological disease pathways. The aim of this review was to identify the newest and most powerful biomarkers and their synergistic interaction for easy and accurate recognition of sJIA and sJIA-MAS, so as to immediately guide clinicians in correct diagnosis and in predicting disease outcomes, the response to treatment, and the risk of relapses. Biomarkers constitute an exciting field of research, especially due to the heterogeneous nature of cytokine storm syndromes (CSSs) in the COVID era. They must be selected with utmost care-a fact supported by the increasingly improved genetic and pathophysiological comprehension of sJIA, but also of CSS-so that new classification systems may soon be developed to define homogeneous groups of patients, although each with a distinct disease.

Calprotectin (S100A8/S100A9) detects inflammatory activity in rheumatoid arthritis patients receiving tocilizumab therapy

Background

Assessing serological inflammation is difficult in tocilizumab (TCZ)-treated rheumatoid arthritis (RA) patients, as standard inflammation parameters, like erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP), are influenced by interleukin-6-receptor inhibition. Calprotectin in the serum, also named S100A8/S100A9, might be a more useful inflammation parameter in TCZ-treated patients.

Methods

Sixty-nine RA patients taking TCZ were included. Serum-calprotectin levels were assessed, as well as ESR, CRP, need for a change in disease-modifying anti-rheumatic drugs due to RA activity (= active RA), and the RA clinical disease activity score (CDAI). Forty-five RA patients taking tumor-necrosis factor-inhibitors (TNFi) were investigated for the same parameters.

Results

TCZ-treated patients with active RA had higher calprotectin values than not active RA patients (4155.5 [inter quartile range 1865.3–6068.3] vs 1040.0 [676.0–1638.0] ng/ml, P < 0.001). A calprotectin cut-off value of 1916.5 ng/ml resulted in a sensitivity and specificity of 80.0 %, respectively, for the detection of RA disease activity. Calprotectin values correlated with CDAI-scores (r = 0.228; P = 0.011). ESR and CRP were less suitable to detect RA activity in TCZ-treated patients. Also TNFi-treated patients with active RA had higher calprotectin values compared to not active RA (5422.0 [3749.0–8150.8] vs 1845.0 [832.0–2569.0] ng/ml, P < 0.001). The calprotectin value with the best sensitivity and specificity for detecting RA activity was 3690.5 ng/ml among TNFi-treated patients.

Conclusion

Calprotectin in the serum can be a useful inflammation parameter despite TCZ-treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02887-7.

Plasma calprotectin - preanalytical stability and interference from hemolysis

As an activation product of neutrophil granulocytes, calprotectin has been widely used in fecal samples for diagnosis and monitoring of patients with inflammatory bowel disease. However, fecal sample collection is cumbersome, and pre-analytical sources of error are plentiful. Therefore, plasma calprotectin is being investigated as a promising new biomarker. To utilize any biomarker, pre-analytical factors such as stability and susceptibility to interference from hemolysis must be established. We present precision estimates, stability results as well as interference study on plasma calprotectin in EDTA-plasma using the Thermo Fischer Phadia 250 EliA^TM Calprotectin immunoassay. Precision was estimated by the use of patient pools as well as internal quality controls provided by the manufacturer. Coefficients of variance were below 6.9% for patient samples. Calprotectin was stable in EDTA plasma after storage at 5-8 °C for up to 4 days, as well as after long-term storage at -20 °C. Susceptibility to interference from hemolysis was high, especially for low concentrations of calprotectin (<50 ng/mL) where hemoglobin levels above 0.02 mmol/L lead to false increase in calprotectin concentrations of up to 100%.

Circulating Calprotectin as a Predictive and Severity Biomarker in Patients with COVID-19

Background: New tools for the assessment and prediction of the severity of hospitalized COVID-19 patients can help direct limited resources to patients with the greatest need. Circulating levels of calprotectin (S100A8/S100A9) reflect inflammatory activity in multiple conditions, and have been described as being elevated in COVID-19 patients, but their measurement is not routinely utilized. The aim of our study was to assess the practical and predictive value of measuring circulating calprotectin levels in patients at admission and during their hospitalization. Methods: Circulating calprotectin levels were measured in 157 hospitalized patients with COVID-19 using an automated quantitative chemiluminescent assay. Results: Circulating calprotectin levels were strongly correlated with changing respiratory supplementation needs of patients. The overall trajectory of circulating calprotectin levels generally correlated with patient improvement or deterioration. Conclusions: Routine measurement of circulating calprotectin levels may offer a valuable tool to assess and monitor hospitalized patients with COVID-19, as well as other acute inflammatory conditions.

Prognostic value of circulating calprotectin levels on the clinical course of COVID-19 differs between serum, heparin, EDTA and citrate sample types

INTRODUCTION

During the recent SARS-CoV-2 pandemic, circulating calprotectin (cCLP) gained interest as biomarker to predict the severity of COVID-19. We aimed to investigate the prognostic value of cCLP measured in serum, heparin, EDTA and citrate plasma.

MATERIALS AND METHODS

COVID-19 patients were prospectively included, in parallel with two SARS-CoV-2 negative control populations. The prognostic value of cCLP was compared with IL-6, CRP, LDH, procalcitonin, and the 4C-mortality score by AUROC analysis.

RESULTS

For the 136 COVID-19 patients, cCLP levels were higher compared to the respective control populations, with significantly higher cCLP levels in serum and heparin than in EDTA or citrate. Higher cCLP levels were obtained for COVID-19 patients with i) severe/critical illness (n = 70), ii) ICU admission (n = 66) and iii) need for mechanical ventilation/ECMO (n = 25), but iv) not in patients who deceased within 30 days (n = 41). The highest discriminatory power (AUC [95% CI]) for each defined outcome was i) CRP (0.835 [0.755-0.914]); ii) EDTA cCLP (0.780 [0.688-0.873]); iii) EDTA cCLP (0.842 [0.758-0.925]) and iv) the 4C-mortality score (0.713 [0.608-0.818]).

CONCLUSION

Measuring cCLP in COVID-19 patients helps the clinician to predict the clinical course of COVID-19. The discriminatory power of EDTA and citrate plasma cCLP levels often outperforms heparin plasma cCLP levels.

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.