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Correlation with mortality and severity at the time of admission was tested with the Spearman coefficient and Mann\u2013Whitney test. Trends over time were tested with the Kruskal\u2013Wallis analysis.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Lymphopenia is severe and constant, with a nadir on day 2 of ICU stay (median 0.555 10\n                      <jats:sup>9<\/jats:sup>\n                      \/L; interquartile range (IQR) 0.450 10\n                      <jats:sup>9<\/jats:sup>\n                      \/L); all lymphocytic subgroups are dramatically reduced in critically ill patients, while CD4\/CD8 ratio remains normal. Neither ferritin nor lymphocyte count follows significant trends in ICU patients. Transferrin saturation is extremely reduced at ICU admission (median 9%; IQR 7%), then significantly increases at days 3 to 6 (median 33%, IQR 26.5%,\n                      <jats:italic>p<\/jats:italic>\n                      value 0.026). The same trend is observed with serum iron levels (median 25.5\u2009\u03bcg\/L, IQR 69\u2009\u03bcg\/L at admission; median 73\u2009\u03bcg\/L, IQR 56\u2009\u03bcg\/L on days 3 to 6) without reaching statistical significance. Hyperferritinemia is constant during intensive care stay: however, its dosage might be helpful in individuating patients developing haemophagocytic lymphohistiocytosis. D-dimer is elevated and progressively increases from admission (median 1319\u2009\u03bcg\/L; IQR 1285\u2009\u03bcg\/L) to days 3 to 6 (median 6820\u2009\u03bcg\/L; IQR 6619\u2009\u03bcg\/L), despite not reaching significant results. We describe trends of all the abovementioned parameters during ICU stay.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>The description of iron metabolism and lymphocyte count in Covid-19 patients admitted to the intensive care unit provided with this paper might allow a wider understanding of SARS-CoV-2 pathophysiology.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s13017-020-00323-2","type":"journal-article","created":{"date-parts":[[2020,6,30]],"date-time":"2020-06-30T03:02:49Z","timestamp":1593486169000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":67,"title":["Iron metabolism and lymphocyte characterisation during Covid-19 infection in ICU patients: an observational cohort study"],"prefix":"10.1186","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-5627-8445","authenticated-orcid":false,"given":"Giuliano","family":"Bolondi","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emanuele","family":"Russo","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Emiliano","family":"Gamberini","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Alessandro","family":"Circelli","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Manlio Cosimo Claudio","family":"Meca","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Etrusca","family":"Brogi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lorenzo","family":"Viola","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Luca","family":"Bissoni","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Venerino","family":"Poletti","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Vanni","family":"Agnoletti","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2020,6,30]]},"reference":[{"key":"323_CR1","first-page":"1","volume":"6736","author":"F Zhou","year":"2020","unstructured":"Zhou F, Yu T, Du R, Fan G, Liu Y, Liu Z, et al. 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