title: Extremely high myoglobin plasma concentrations producing hook effect in a critically ill patient.
abstract: BACKGROUND
  A 21-year old female suffered a cardiac arrest after a one week history of viral illness later shown to be caused by influenza B. The patient required extended cardiopulmonary resuscitation and had further complications including compartment syndrome.
  
  
  METHODS
  Plasma myoglobin concentration was measured using the Roche Diagnostics electrochemiluminescent myoglobin assay.
  
  
  RESULTS
  The myoglobin concentration was 205,590 μg/l in an undiluted specimen, consistent with severe rhabdomyolysis. Subsequent myoglobin concentrations measured two days later showed dramatic decreases to approximately 1000 μg/l, raising suspicion of a hook effect. Dilution and re-analysis of the specimens revealed that the actual myoglobin concentrations were >395,000 μg/l, with one specimen possessing an estimated myoglobin concentration of >600,000 μg/l. Interestingly, three specimens from this patient did not show evidence of hook effect, with undiluted specimens producing myoglobin concentrations as high as 284,000 μg/l. Retrospective analysis of myoglobin results over an 8-year period did not reveal other cases with suspicion of hook effect. The case patient had the highest myoglobin concentrations out of 7301 specimens.
  
  
  CONCLUSIONS
  This case illustrates that while the Roche myoglobin assay has a very wide dynamic range, hook effect can occur with extremely high concentrations of plasma myoglobin.
authors.affiliation: Department of Pathology, University of Iowa Hospitals and Clinics, Iowa City, IA 52242, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Kurt-Mangold
authors.forename: Denny
authors.initials: D
authors.lastname: Drees
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Krasowski
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D009211:Myoglobin / Q000097:blood* / Q000302:isolation & purification; D012189:Retrospective Studies; D012206:Rhabdomyolysis / Q000097:blood* / Q000175:diagnosis; D055815:Young Adult
chemical_list: D009211:Myoglobin