Soluble fms-like tyrosine kinase-1: a potential early predictor of respiratory failure in COVID-19 patients
-
José L. Eguiburu-Jaime
, Aitor Delmiro , Antonio Lalueza , Pedro L. Valenzuela , José M. Aguado , Carlos Lumbreras , Joaquín Arenas , Miguel A. Martín , Alejandro Luciaund Elena A. López-Jiménez
To the Editor,
A main feature of the most severely affected patients with coronavirus disease 2019 (COVID-19) is hypoxemic respiratory failure from acute respiratory distress syndrome (ARDS). The presence of intussusceptive (‘splitting’) angiogenesis and other vascular features has been reported to distinguish the lungs of patients who died from respiratory failure due to COVID-19 from those of individuals who died from influenza [1]. Angiogenesis is chiefly regulated by vascular endothelial growth factor (VEGF) and its associated family members, whose proangiogenic activity is mediated through their engagement with VEGF receptor 1 (VEGFR1, also known as ‘fms-like tyrosine kinase 1’ or Flt1) and VEGFR2. Another member of the VEGF family, placental growth factor (PlGF), stimulates endothelial healing and recruitment of mononuclear bone marrow cells as well as microvascular angiogenesis through engagement with Flt1, which is expressed in many tissues including the lung [2]. Alternative splicing of Flt1 pre-mRNA creates the soluble form of this receptor, known as ‘sFlt1’, which binds and antagonizes VEGF and PlGF signal [3]. Excess levels of sFlt1 induce endothelial dysfunction in hypoxia and contribute to cardiovascular disease [4].
In this single-center prospective cohort study, we aimed to analyze the potential role of sFlt-1 and PlGF, together with other ‘traditional’ biomarkers, as predictors of respiratory failure in patients hospitalized with COVID-19.
We enrolled patients hospitalized with COVID-19 at Hospital 12 de Octubre (Madrid, Spain) between 03/12/2020–04/20/2020. The study was approved by the local Ethics Committee (reference#20/222 and 20/117) and adhered to the Declaration of Helsinki. Patients’ main characteristics along with their progress and complications during hospitalization were extracted from electronic medical records. COVID-19 was confirmed via SARS-CoV-2 real-time reverse transcription polymerase chain reaction (nasopharyngeal swab or sputum samples). Respiratory failure was defined as the presence of an arterial oxygen partial pressure/fractional inspired oxygen ratio ≤200 mmHg or the need for mechanical ventilation (non-invasive positive pressure ventilation including high-flow nasal cannula oxygen, or invasive mechanical ventilation). Respiratory failure could occur at any time during hospital admission.
Blood samples were obtained within the first 48 h of hospitalization. Plasma sFlt1/PlG1 concentrations were measured using automated immunoassays (Cobas e601, Roche Diagnostics, Risch-Rotkreuz, Switzerland) following manufacturer’s instructions. Other major blood biomarkers associated with inflammation and/or COVID-19 were also determined (e.g., lactate dehydrogenase (LDH), C-reactive protein (CRP), lymphocyte count, albumin) as reported elsewhere [5].
To determine the clinical utility of blood biomarkers for prediction of respiratory failure (vs. not suffering this condition) in patients hospitalized with COVID-19, we used receiver operating characteristic (ROC) curve analysis. The sensitivity, specificity, positive and negative predictive values for the computed cutoff values were also calculated.
One hundred eleven hospitalized patients with confirmed COVID-19 were enrolled, of whom 52 (46.8% of total) developed respiratory failure 1–9 days following blood extraction (median, 2.5 days). Thirty-four (31% of total) of the patients died, most (n=32) having developed respiratory failure.
Significant differences were found for most blood biomarkers between patients who developed respiratory failure and those who did not (Table 1). On the other hand, four biomarkers (sFlt1, LDH, CRP and lymphocyte count) had area under the curve values >0.7 to predict the occurrence of respiratory failure in patients hospitalized with COVID-19, with sensitivity and specificity values ranging from 75.0 to 88.2% and from 52.8 to 75.4%, respectively, and with sFlt1 showing the best predictive accuracy (Figure 1).
Baseline characteristics and main results by group.
| No respiratory failure | Respiratory failure | p-Value between groups | |
|---|---|---|---|
| n=59 | n=52 | ||
| Age, years | 71 [59.5, 80.5] | 74 [62.0, 81.2] | 0.304 |
| Sex | |||
| Male | 31 (52.5%) | 37 (71.1%) | 0.053 |
| Female | 28 (47.5%) | 15 (28.9%) | 0.053 |
| Signs and symptoms on admission | |||
| Days with symptoms | 7 [4, 8] | 5 [4, 7] | 0.027 |
| Cough | 48 (81.4%) | 39 (75.0%) | 0.491 |
| Dyspnea | 27 (45.8%) | 36 (69.2%) | 0.021 |
| Myalgia | 24 (40.7%) | 15 (28.8%) | 0.234 |
| Diarrhoea | 19 (32.2%) | 16 (30.8%) | 1.000 |
| Expectoration | 12 (20.3%) | 11 (21.1%) | 1.000 |
| Vomit | 9 (15.2%) | 4 (7.7%) | 0.251 |
| Bronchospasm | 2 (3.4%) | 3 (5.8%) | 0.664 |
| Vital signs on admission | |||
| Systolic blood pressure, mmHg | 130 [121, 144] | 125 [116, 138] | 0.116 |
| Heart rate, beats/min | 87 [79, 98] | 89 [74, 97] | 0.453 |
| Body temperature, °C | 37.4 [36.9, 38.0] | 37.8 [37.3, 28.4] | 0.011 |
| Respiratory rate, breaths/min | 18 [16, 20] | 21 [18, 23] | 0.001 |
| Arterial oxygen saturation, % | 96 [93, 98] | 92 [89, 94] | <0.001 |
| PaO2 (mmHg)/FiO2 (%), mmHg | 438 [345, 471] | 305 [263, 433] | 0.012 |
| Comorbidities | |||
| Hypertension | 29 (49.2%) | 34 (65.4%) | 0.124 |
| Influenza vaccination (last year) | 31(52.5%) | 30 (57.7%) | 0.703 |
| Dyslipidemia | 19 (32.2%) | 23 (44.2%) | 0.240 |
| Obesity | 16 (27.1%) | 18 (34.6%) | 0.416 |
| Diabetes | 15 (25.4%) | 14 (26.9%) | 1.000 |
| Malignancies | 7 (11.9%) | 9 (17.3%) | 0.433 |
| Chronic heart failure | 6 (10.2%) | 9 (15.2%) | 0.405 |
| Acute myocardial infarction | 6 (10.2%) | 6 (11.5%) | 1.000 |
| Chronic obstructive pulmonary disease | 1 (1.7%) | 10 (19.2%) | 0.003 |
| Asthma | 7 (11.9%) | 3 (5.8%) | 0.331 |
| Severe nephropathies | 4 (6.8%) | 6 (11.2%) | 0.501 |
| Liver diseases | 3 (5.1%) | 7 (11.9%) | 0.185 |
| Transplant | 6 (10.2%) | 4 (6.8%) | 0.748 |
| Treatments on admission | |||
| Antihypertensive drugs | 28 (53.8%) | 32 (54.2%) | 0.252 |
| ACE inhibitors | 17 (32.7%) | 13 (22.0%) | 0.675 |
| ARB | 10 (16.9%) | 14 (23.7%) | 0.250 |
| Other | 1 (1.7%) | 5 (8.5%) | 0.097 |
| ASA | 11 (18.6%) | 10 (16.9%) | 1.000 |
| Anticoagulants | 7 (11.9%) | 12 (23.1%) | 0.136 |
| Steroids | 5 (8.5%) | 6 (10.2%) | 0.753 |
| Treatments during hospitalization | |||
| Lopinavir/ritonavir | 32 (54.2%) | 37 (71.1%) | 0.079 |
| Hydroxychloroquine | 55 (93.2%) | 47 (90.4%) | 0.737 |
| Tocilizumab | 2 (3.4%) | 11 (21.1%) | 0.006 |
| Antibiotics | 58 (98.3%) | 51 (98.1%) | 1.000 |
| Steroids | 16 (27.1%) | 36 (69.2%) | <0.001 |
| Scores | |||
| SOFA | 1.29 ± 1.82 | 2.28 ± 1.63 | 0.005 |
| qSOFA | 0.28 ± 0.45 | 0.71 ± 0.70 | <0.001 |
| Charlson comborbidity index | 3.41 ± 2.13 | 4.39 ± 2.30 | 0.024 |
| Exitus | 3 (5.1%) | 33 (63.5%) | <0.001 |
| eGFR (CKD-EPI, mL/min per 1.73 m2) | 20.3 [15.1, 26.1] | 24.0 [18.9, 30.5] | 0.046 |
| Blood biochemical variables | |||
| sFlt1, ng/L | 88.2 [77.6, 98.6] | 118.8 [98.3, 139.4] | <0.001 |
| LDH, U/L | 287 [250, 348] | 404 [342, 476] | <0.001 |
| CRP, mg/L | 44.3 [22.0, 100.4] | 105.9 [70.8, 177.9] | 0.001 |
| Lymphocyte count (×109/L) | 1.1 [0.9, 1.4] | 0.8 [0.6, 1.0] | 0.003 |
| AST/ALT | 1.35 [1.03, 1.68] | 1.56 [1.26, 1.86] | 0.018 |
| PlGF, ng/L | 84.6 [58.9, 97.5] | 71.4 [49.8, 87.0] | 0.022 |
| Albumin, g/L | 37.6 [34.0, 39.8] | 35.9 [32.7, 38.0] | 0.066 |
| RDW, % | 13.7 [13.4, 14.5] | 14.1 [13.6, 17.3] | 0.143 |
| Ferritin, µg/L | 761 [336, 1,250] | 1,016 [549, 2,183] | 0.219 |
| sFlt1/PlGF | 4.24 [3.55, 6.00] | 4.77 [3.83, 6.17] | 0.219 |
Data are mean [interquartile range] for age and vital signs and symptoms on admission, median [interquartile range] for days with symptoms, mean ± standard deviation for scores, and n (%) for the rest of variables. p-Values corresponds to the comparisons between groups with the Mood ´s median test or with the χ2 or Fisher’s test (for proportions). Significant p-values (<0.05) are in bold. ACE, angiotensin converting enzyme; ARB, angiotensin-II receptor blockers; ALT, alanine transaminase; ASA, acetylsalicylic acid; AST, aspartate transaminase; CKD-EPI, chronic kidney disease epidemiology collaboration equation; CRP, C-reactive protein; FiO2, fractional inspired oxygen; eGFR, estimated glomerular filtration rate; LDH, lactate dehydrogenase; PaO2, arterial oxygen partial pressure; PlGF, placental growth factor; RDW, red blood cell distribution width; ROC, receiver operating characteristic; sFlt1, soluble fms-like tyrosine kinase 1; SOFA, sequential organ failure assessment.

Area under the curve (AUC), sensitivity, specificity, cut off points and Youden Index (J) values for the biomarkers with the highest AUC (>0.70) to predict occurrence of respiratory failure in patients hospitalized with COVID-19.
CRP, C-reactive protein; LDH, lactate dehydrogenase; sFlt1, soluble fms-like tyrosine kinase 1.
Endothelial disease is an essential part of the pathological response to severe COVID-19, which leads to respiratory failure, multiorgan dysfunction and thrombosis [1]. Because the vascular endothelium depends on proangiogenic factors, excess release of antiangiogenic factors (e.g., sFlt1) is a possible cause of the endothelial dysfunction observed in patients with COVID-19. Yet, sFlt1 and PlGF (an anti and proangiogenic factor, respectively) have received scant attention in the context of this disease. Giardini et al. [6] reported higher values of sFlt1 and sFlt1/PlGF ratio in patients with COVID-19–associated pneumonia than in healthy controls. Dupont et al. [7] reported high sFlt1 circulating levels in patients severely affected with COVID-19, finding a correlation between sFlt1 and an endothelial dysfunction biomarker, soluble vascular cell adhesion molecule-1. On the other hand, the finding of a potential role of angiogenic processes in patients with COVID-19 opens the door for new therapeutic approaches. Low-dose aspirin (60–100 mg/day) inhibits the expression of sFlt1 in hypoxia-induced human cytotrophoblasts [8]. It can be thus hypothesized that aspirin administration might diminish the hypoxemic respiratory failure due to COVID-19–associated ARDS in critically ill patients. In addition, sFlt1 values could guide the timing of steroid administration.
To our knowledge, this is the first study with sFlt1 as an early predictor of respiratory failure in the context of COVID-19. Our findings suggest that this biomarker might identify a subgroup of hospitalized patients with this condition who are at higher risk of developing respiratory failure, and could thus help physicians to better triage these patients.
Funding source: Spanish Ministry of Science and Innovation, Instituto de Salud Carlos III
Award Identifier / Grant number: COVID-19 research call COV20/00181
Funding source: Spanish Ministry of Economy and Competitiveness and Fondos Feder
Award Identifier / Grant number: PI18/00139
Research funding: This study was supported by the Spanish Ministry of Science and Innovation, Instituto de Salud Carlos III (COVID-19 research call COV20/00181) co‐financed by the European Development Regional Fund “A way to achieve Europe”. Research by A.L. is funded by the Spanish Ministry of Economy and Competitiveness and Fondos Feder (grant PI18/00139). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Competing interests: Authors state no conflict of interest.
Informed consent: Informed consent was obtained from all individuals included in this study.
Ethical approval: The study was approved by the local Ethics Committee (reference#20/222 and 20/117) and adhered to the Declaration of Helsinki.
References
1. Ackermann, M, Verleden, SE, Kuehnel, M, Haverich, A, Welte, T, Laenger, F, et al.. Pulmonary vascular endothelialitis, thrombosis, and angiogenesis in Covid-19. N Engl J Med 2020;383:120–8. https://doi.org/10.1056/nejmoa2015432.Suche in Google Scholar PubMed PubMed Central
2. Mazure, N, Brahimi-Horn, M, Pouysségur, J. Protein kinases and the hypoxia-inducible factor-1, two switches in angiogenesis. Curr Pharmaceut Des 2003;9:531–41. https://doi.org/10.2174/1381612033391469.Suche in Google Scholar PubMed
3. Cindrova-Davies, T, Sanders, DA, Burton, GJ, Charnock-Jones, DS. Soluble FLT1 sensitizes endothelial cells to inflammatory cytokines by antagonizing VEGF receptor-mediated signalling. Cardiovasc Res 2011;89:671–9. https://doi.org/10.1093/cvr/cvq346.Suche in Google Scholar PubMed PubMed Central
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6. Giardini, V, Carrer, A, Casati, M, Contro, E, Vergani, P, Gambacorti-Passerini, C. Increased sFLT-1/PlGF ratio in COVID-19: a novel link to angiotensin II-mediated endothelial dysfunction. Am J Hematol 2020;95:E188–91. https://doi.org/10.1002/ajh.25882.Suche in Google Scholar PubMed PubMed Central
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© 2021 Walter de Gruyter GmbH, Berlin/Boston
Artikel in diesem Heft
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- Updates on liquid biopsy: current trends and future perspectives for clinical application in solid tumors
- The underestimated issue of non-reproducible cardiac troponin I and T results: case series and systematic review of the literature
- Opinion Paper
- Benefits, limitations and controversies on patient-based real-time quality control (PBRTQC) and the evidence behind the practice
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- General Clinical Chemistry and Laboratory Medicine
- Incidence, characteristics and outcomes among inpatient, outpatient and emergency department with reported high critical serum potassium values
- Clinical usefulness of drug-laboratory test interaction alerts: a multicentre survey
- Integrating quality assurance in autoimmunity: the changing face of the automated ANA IIF test
- Plasma thiol/disulphide homeostasis changes in patients with restless legs syndrome
- Reference Values and Biological Variations
- High-resolution pediatric reference intervals for 15 biochemical analytes described using fractional polynomials
- Continuous reference intervals for leukocyte telomere length in children: the method matters
- Hematology and Coagulation
- Using machine learning to identify clotted specimens in coagulation testing
- Cardiovascular Diseases
- Long term pronostic value of suPAR in chronic heart failure: reclassification of patients with low MAGGIC score
- Infectious Diseases
- Monocyte distribution width (MDW) parameter as a sepsis indicator in intensive care units
- A low level of CD16pos monocytes in SARS-CoV-2 infected patients is a marker of severity
- Thrombin generation in patients with COVID-19 with and without thromboprophylaxis
- Corrigendum
- Applying the concept of uncertainty to the sFlt-1/PlGF cut-offs for diagnosis and prognosis of preeclampsia
- Letters to the Editors
- Additional approaches for identifying non-reproducible cardiac troponin results
- Paediatric reference intervals for ionised calcium – a data mining approach
- A case of interference in testosterone, DHEA-S and progesterone measurements by second generation immunoassays
- Lack of cross-reactivity between anti-A IgG isoagglutinins and anti-SARS-CoV-2 IgG antibodies
- Artefactual bands on urine protein immunofixation gels
- A case of methaemoglobinaemia interference on the WDF channel on Sysmex XN-Series analysers
- Soluble fms-like tyrosine kinase-1: a potential early predictor of respiratory failure in COVID-19 patients
- Serendipitous detection of α1-antitrypsin deficiency: a single institution’s experience over a 32 month period
- The activated partial thromboplastin time may not reveal even severe fibrinogen deficiency
- Influence of C-reactive protein on thrombin generation assay
- Inappropriate extrapolations abound in fecal microbiota research
Artikel in diesem Heft
- Frontmatter
- Editorial
- Machine learning and coagulation testing: the next big thing in hemostasis investigations?
- Reviews
- Updates on liquid biopsy: current trends and future perspectives for clinical application in solid tumors
- The underestimated issue of non-reproducible cardiac troponin I and T results: case series and systematic review of the literature
- Opinion Paper
- Benefits, limitations and controversies on patient-based real-time quality control (PBRTQC) and the evidence behind the practice
- Genetics and Molecular Diagnostics
- ctDNA from body fluids is an adequate source for EGFR biomarker testing in advanced lung adenocarcinoma
- General Clinical Chemistry and Laboratory Medicine
- Incidence, characteristics and outcomes among inpatient, outpatient and emergency department with reported high critical serum potassium values
- Clinical usefulness of drug-laboratory test interaction alerts: a multicentre survey
- Integrating quality assurance in autoimmunity: the changing face of the automated ANA IIF test
- Plasma thiol/disulphide homeostasis changes in patients with restless legs syndrome
- Reference Values and Biological Variations
- High-resolution pediatric reference intervals for 15 biochemical analytes described using fractional polynomials
- Continuous reference intervals for leukocyte telomere length in children: the method matters
- Hematology and Coagulation
- Using machine learning to identify clotted specimens in coagulation testing
- Cardiovascular Diseases
- Long term pronostic value of suPAR in chronic heart failure: reclassification of patients with low MAGGIC score
- Infectious Diseases
- Monocyte distribution width (MDW) parameter as a sepsis indicator in intensive care units
- A low level of CD16pos monocytes in SARS-CoV-2 infected patients is a marker of severity
- Thrombin generation in patients with COVID-19 with and without thromboprophylaxis
- Corrigendum
- Applying the concept of uncertainty to the sFlt-1/PlGF cut-offs for diagnosis and prognosis of preeclampsia
- Letters to the Editors
- Additional approaches for identifying non-reproducible cardiac troponin results
- Paediatric reference intervals for ionised calcium – a data mining approach
- A case of interference in testosterone, DHEA-S and progesterone measurements by second generation immunoassays
- Lack of cross-reactivity between anti-A IgG isoagglutinins and anti-SARS-CoV-2 IgG antibodies
- Artefactual bands on urine protein immunofixation gels
- A case of methaemoglobinaemia interference on the WDF channel on Sysmex XN-Series analysers
- Soluble fms-like tyrosine kinase-1: a potential early predictor of respiratory failure in COVID-19 patients
- Serendipitous detection of α1-antitrypsin deficiency: a single institution’s experience over a 32 month period
- The activated partial thromboplastin time may not reveal even severe fibrinogen deficiency
- Influence of C-reactive protein on thrombin generation assay
- Inappropriate extrapolations abound in fecal microbiota research