title: Underestimation of plasma level of factor V coagulant activity and fibrinogen concentration together with prolonged prothrombin time, activated partial thromboplastin time and thrombin time can result from pre-analytical very low calcium level in citrated sample tube.
abstract: BACKGROUND
  Pre-analytical phase is a critical step in the haemostasis laboratory cycle. Numerous variations affect tests results, and it is crucial to detect them in order to reject improper specimens before reporting test results. Comparing to prior results or requesting, a repeat sample can help in pre-analytical irregularity assessment.
  
  
  METHODS
  Each time a sample addressed to our laboratory displayed aberrant results or discordant with a prior report, another specimen was asked and both were analysed through calcium (Ca) level, prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT), fibrinogen concentration, factor II, factor VII+X and factor V coagulant activity measurements. Among these, all the primary citrated samples from inpatients without anticoagulant treatment, displaying very low calcium level ('Ca 0' samples), were selected for this 2 years study.
  
  
  RESULTS
  A total of 17 samples could be identified. Ca level in their paired repeat samples was always >1.00 mmol/L. Coagulation testing for 'Ca 0' samples showed a significant prolongation of PT, APTT, TT and a significant decrease for fibrinogen concentration and factor V coagulant activity.
  
  
  CONCLUSIONS
  We identified factor V coagulant activity, as the parameter with the most important variation in case of very low calcium level in presumed citrated sample tubes probably contaminated with EDTA.
authors.affiliation: Laboratoire d'Hématologie, EFS Bourgogne - Franche-Comté, Besançon, France.
authors.forename: C
authors.initials: C
authors.lastname: d'Audigier
authors.affiliation: Hôpital Saint-Antoine, Service d'Hématologie Biologique, AP-HP, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Delassasseigne
authors.affiliation: Hôpital Saint-Antoine, Service d'Hématologie Biologique, AP-HP, Paris, France.|Université Pierre et Marie Curie, Paris, France.
authors.forename: A
authors.initials: A
authors.lastname: Robert
authors.affiliation: Laboratoire d'hématologie biologique, CHRU de Nancy, Vandœuvre-lès-Nancy, France.
authors.forename: V
authors.initials: V
authors.lastname: Eschwège
mesh_terms: D001777:Blood Coagulation; D001778:Blood Coagulation Disorders / Q000097:blood / Q000175:diagnosis; D001780:Blood Coagulation Tests; D005165:Factor V; D005340:Fibrinogen; D006801:Humans; D010314:Partial Thromboplastin Time / Q000379:methods / Q000592:standards; D011517:Prothrombin Time / Q000379:methods / Q000592:standards; D013918:Thrombin Time / Q000379:methods / Q000592:standards
chemical_list: D005165:Factor V; D005340:Fibrinogen
keywords: Factor V; activated partial thromboplastin time; calcium; fibrinogen; prothrombin time; thrombin time