{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,16]],"date-time":"2026-01-16T06:13:50Z","timestamp":1768544030985,"version":"3.49.0"},"reference-count":33,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2026,1,12]],"date-time":"2026-01-12T00:00:00Z","timestamp":1768176000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Vicerrector\u00eda de Investigaci\u00f3n y Postgrado, Universidad Cat\u00f3lica de Temuco","award":["2023FIAS-NG-04"],"award-info":[{"award-number":["2023FIAS-NG-04"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Medicina"],"abstract":"<jats:p>Background and Objectives: Neutrophil extracellular traps (NETs) have been linked to hypercoagulability, immunothrombosis, and organ injury in COVID-19. Digital morphology of peripheral blood smears enables the identification of NET-compatible appearances (NET-like) in circulation, and associations between NET-like derived indices and clinical outcomes have been reported. However, evidence at hospital admission that relates smear NET-like burden to systemic inflammation and clinical severity remains limited. We therefore aimed to compare the burden of NET-like structures on admission smears according to disease severity and systemic inflammatory markers. Materials and Methods: We included 50 consecutively enrolled adults hospitalized for COVID-19; samples were obtained within 24 h of admission. Severity was defined by the World Health Organization Clinical Progression Scale and grouped as moderate or severe. C-reactive protein (CRP), ferritin, and complete blood counts were measured; the neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) were calculated. Digital morphology assessed 200 leukocytes per patient; the presence of morphological abnormalities, including NET-like events per patient, was recorded. We additionally quantified NET-like events per 100 white blood cells (NET-like\/100 WBC) and the neutrophil extracellular trap\u2013segmented neutrophil ratio (NNSR). Results: At admission, CRP, ferritin, NLR, and PLR of patients were above method-specific reference intervals. NET-like events were identified in 66% of patients. NET-like\/100 WBC correlated positively with NLR (r = 0.312; p &lt; 0.05). Patients with severe COVID-19 had higher NET-like\/100 WBC than those with moderate disease (5.8 \u00b1 7.34 vs. 14.14 \u00b1 15.12; p = 0.0294). Conclusions: Digital morphological identification of NET-like structures on peripheral blood smears is frequent at admission and is associated with systemic inflammatory burden and with greater COVID-19 severity. These findings support the potential complementary value of reporting NET-like events for initial risk stratification in the clinical laboratory.<\/jats:p>","DOI":"10.3390\/medicina62010153","type":"journal-article","created":{"date-parts":[[2026,1,13]],"date-time":"2026-01-13T08:17:32Z","timestamp":1768292252000},"page":"153","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["NET-like Events on Peripheral Blood Smears at Admission: Association with Disease Severity and Systemic Inflammation in Hospitalized COVID-19 Patients"],"prefix":"10.3390","volume":"62","author":[{"ORCID":"https:\/\/orcid.org\/0009-0007-4372-0824","authenticated-orcid":false,"given":"Alexy","family":"Rosales","sequence":"first","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0325-743X","authenticated-orcid":false,"given":"Rodrigo","family":"Boguen","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6278-7369","authenticated-orcid":false,"given":"Felipe","family":"Garrido","sequence":"additional","affiliation":[{"name":"Laboratorio Cl\u00ednico, Hospital Dr. Hern\u00e1n Henr\u00edquez Aravena, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0007-8347-7101","authenticated-orcid":false,"given":"Francisco","family":"Qui\u00f1ones","sequence":"additional","affiliation":[{"name":"Laboratorio Cl\u00ednico, Hospital Dr. Hern\u00e1n Henr\u00edquez Aravena, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0004-3077-5795","authenticated-orcid":false,"given":"Jos\u00e9","family":"Barros","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0009-5578-6446","authenticated-orcid":false,"given":"Fabi\u00e1n","family":"Baeza","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0009-0005-7527-8474","authenticated-orcid":false,"given":"Josefa","family":"D\u00edaz","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Salvador","family":"Fuentes","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9803-9752","authenticated-orcid":false,"given":"Pablo","family":"Letelier","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4872-9821","authenticated-orcid":false,"given":"Neftal\u00ed","family":"Guzm\u00e1n","sequence":"additional","affiliation":[{"name":"Laboratorio de Investigaci\u00f3n en Salud de Precisi\u00f3n, Centro de Investigaci\u00f3n en Ciencias de la Salud, Departamento de Procesos Diagn\u00f3sticos y Evaluaci\u00f3n, Facultad de Ciencias de la Salud, Universidad Cat\u00f3lica de Temuco, Manuel Montt 56, Temuco 4780000, Chile"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2026,1,12]]},"reference":[{"key":"ref_1","unstructured":"World Health Organization (2025). 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