title: The transferrin/log(ferritin) ratio: a new tool for the diagnosis of iron deficiency anemia.
abstract: BACKGROUND
  Serum ferritin is the best single laboratory test to diagnose iron deficiency anemia (IDA). Ferritin levels <20 μg/L are highly specific for IDA, and ferritin levels >100 μg/L usually exclude IDA. However, ferritin concentrations between 20 and 100 μg/L are often inconclusive. The objective of this study was to improve the diagnosis of IDA when ferritin levels are inconclusive.
  
  
  METHODS
  We evaluated the predictive performance of classic (ferritin, mean corpuscular volume, transferrin and serum iron) and modern [reticulocyte hemoglobin content, serum transferrin receptor and soluble transferrin receptor (sTfR)/log(ferr)] iron status parameters to diagnose IDA in 2084 anemic, non-hospitalized patients. The results were validated in an independent cohort of 274 anemic patients.
  
  
  RESULTS
  In our study population, 29% (595 patients) of the patients had a ferritin level between 20 and 100 μg/L, hampering diagnosis of IDA. None of the classic or modern parameters was capable of completely separating the IDA population from the non-IDA population. However, using a new parameter, the transferrin/log(ferritin) ratio, the IDA and non-IDA populations can be completely separated. At a cut-off value of 1.70, the transferrin/log(ferritin) ratio indicates IDA in 29% of the patients with inconclusive ferritin levels.
  
  
  CONCLUSIONS
  The transferrin/log(ferritin) ratio is a practical new tool that improves diagnosis of iron deficiency when ferritin levels are inconclusive.
authors.affiliation: Department of Clinical Chemistry and Hematology, Albert Schweitzer Hospital, Dordrecht, The Netherlands. r.castel@asz.nl
authors.forename: Rob
authors.initials: R
authors.lastname: Castel
authors.forename: Martine G H M
authors.initials: MG
authors.lastname: Tax
authors.forename: Jolanda
authors.initials: J
authors.lastname: Droogendijk
authors.forename: Math P G
authors.initials: MP
authors.lastname: Leers
authors.forename: Ruud
authors.initials: R
authors.lastname: Beukers
authors.forename: Mark-David
authors.initials: MD
authors.lastname: Levin
authors.forename: Pieter
authors.initials: P
authors.lastname: Sonneveld
authors.forename: Paul B
authors.initials: PB
authors.lastname: Berendes
mesh_terms: D000293:Adolescent; D000328:Adult; D018798:Anemia, Iron-Deficiency / Q000097:blood / Q000175:diagnosis*; D005260:Female; D005293:Ferritins / Q000032:analysis / Q000097:blood*; D006454:Hemoglobins / Q000378:metabolism; D006801:Humans; D007501:Iron / Q000097:blood; D000090463:Iron Deficiencies; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D014168:Transferrin / Q000032:analysis / Q000378:metabolism*; D055815:Young Adult
chemical_list: D006454:Hemoglobins; D014168:Transferrin; D005293:Ferritins; D007501:Iron