title: An international study of how laboratories handle and evaluate patient samples after detecting an unexpected APTT prolongation.
abstract: BACKGROUND
  An unexpectedly detected prolonged activated partial thromboplastin time (APTT) can be a harmless laboratory finding, but can also reflect a thrombotic tendency or a bleeding disorder. The assistance of laboratory professionals in the interpretation of an unexpectedly detected prolonged APTT (uAPTT) is often required. The way in which uAPTTs are evaluated in laboratories was assessed in this international study with the aim of determining whether laboratory professionals are able to fulfill this need.
  
  
  METHODS
  Postanalytical practices after uAPTT were investigated and the mixing study methodology (if used) was studied by circulating a case report with a questionnaire to staff in the invited laboratories. In addition, the interpretations of those staff regarding the presence or absence of inhibitors in three APTT mixing study scenarios were examined.
  
  
  RESULTS
  Large within- and between-country variations were detected in both postanalytical practices and mixing study methodologies among the 990 responding laboratories, 90% of which were in 13 countries. Shortcomings regarding the investigation of uAPTTs leading to potentially incorrect or delayed clinical diagnoses were found in 88% of the laboratories. Of the laboratories to which the interpretative questions were sent, 49% interpreted all mixing study scenarios correctly. uAPTTs were investigated appropriately and all mixing study scenarios interpreted correctly in parallel in only 9.6% of the participating laboratories.
  
  
  CONCLUSIONS
  The clinical requirement for the assistance of laboratory professionals in the interpretation of uAPTTs cannot be met at most of the participating laboratories. Laboratory professionals should be trained in the evaluation of ordinary laboratory tests, such as that for uAPTTs.
authors.forename: Éva
authors.initials: É
authors.lastname: Ajzner
authors.forename: Dunja
authors.initials: D
authors.lastname: Rogic
authors.forename: Piet
authors.initials: P
authors.lastname: Meijer
authors.forename: Ann Helen
authors.initials: AH
authors.lastname: Kristoffersen
authors.forename: Paolo
authors.initials: P
authors.lastname: Carraro
authors.forename: Eser
authors.initials: E
authors.lastname: Sozmen
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Faria
authors.forename: Sverre
authors.initials: S
authors.lastname: Sandberg
mesh_terms: D001780:Blood Coagulation Tests / Q000379:methods*; D002648:Child; D005260:Female; D006801:Humans; D007391:International Cooperation; D017056:Medical Laboratory Personnel; D010314:Partial Thromboplastin Time / Q000379:methods* / Q000639:trends; D011361:Professional Competence; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires