Background: Blood test results required for the evaluation of anemia are considered difficult to interpret after red blood cell transfusion. However, this hypothesis is neither supported by a strong physiological rationale nor is it evidence based.
Methods: We conducted a prospective multicenter study to compare the values of key assays prior to and after a course of red blood cell transfusion in the emergency or internal medicine units in 4 university hospitals. The following parameters were measured prior to and within 48 to 72 hours after transfusion: complete blood count with reticulocyte count, direct Coombs' test, ferritin, transferrin saturation, soluble transferrin receptor, serum and erythrocyte folate, cobalamin, lactate dehydrogenase, bilirubin, haptoglobin, and C-reactive protein. We investigated the impact of transfusion on these parameters and assessed whether abnormal values prior to the transfusion became normal after transfusion (or conversely).
Results: There were 77 patients included in the study. Changes in mean values of mean corpuscular volume, soluble transferrin receptor, erythrocyte folate, cobalamin, haptoglobin, lactate dehydrogenase, C-reactive protein, and direct Coombs' test were not statistically significant. Changes in reticulocyte count, ferritin, transferrin saturation, serum folate, and total bilirubin concentrations were statistically significant, but they remained in the same diagnostic category (normal or abnormal) in 79% to 98% of the cases; 97% of patients with iron deficiency still had low ferritin or transferrin saturation after a transfusion.
Conclusion: Blood tests performed after a one-time red blood cell transfusion can be used to establish the cause of anemia when they have not been performed before.
Keywords: Anemia; Cobalamin; Ferritin; Folate; Haptoglobin; Red blood cell transfusion; Transferrin saturation.
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