title: Evaluation of the usefulness of a D dimer test in combination with clinical pretest probability score in the prediction and exclusion of Venous Thromboembolism by medical residents.
abstract: BACKGROUND
  Venous thromboembolism (VTE) requires urgent diagnosis and treatment to avoid related complications. Clinical presentations of VTE are nonspecific and require definitive confirmation by imaging techniques. A clinical pretest probability (PTP) score system helps predict VTE and reduces the need for costly imaging studies. d-dimer (DD) assay has been used to screen patients for VTE and has shown to be specific for VTE. The combined use of PTP and DD assay may improve exclusion of VTE and safely avoid imaging studies.
  
  
  METHODS
  We prospectively used the Wells PTP score and a DD test to evaluate 230 consecutive patients who presented with VTE symptoms. The receiver operating characteristic curve was used to identify a new DD cutoff value, which was applied to VTE diagnosis and compared with the upper limit of locally established reference range for prediction of thrombosis alone and in combination with the clinical PTP score.
  
  
  RESULTS
  We evaluated 118 patients with VTE symptoms fulfilling the inclusion criteria, 64 (54.2%) with clinically suspected deep vein thrombosis (DVT) and 54 (45.8%) with symptoms of pulmonary embolism (PE). The PTP was low in 28 (43.8%) and moderate/high in 36 (56.25%) of the suspected DVT patients, and low in 29 (53.7%) and moderate/high in 25 (46.3%) of the suspected PE patients. Eighteen cases were confirmed by imaging studies: 9 DVT and 9 PE. The agreement between confirmed cases and PTP was significant with PE but not DVT. The negative predictive value for both DVT and PE with current DD cutoff value of <250 μg/L DDU was 100%, whereas with the calculated cutoff the NPV was 88%.
  
  
  CONCLUSIONS
  We confirm that PTP score is valuable tool for medical residents to improve the detection accuracy of VTE, especially for PE. The DD cutoff value of 250 μg/L FEU is ideal for excluding most cases of low PTP; however, the calculated cutoff was less specific for the exclusion of VTE.
authors.affiliation: Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
authors.forename: Tarek
authors.initials: T
authors.lastname: Owaidah
authors.affiliation: Department of Pathology, College of medicine, Qassim University, Buraidah, Saudi Arabia.
authors.forename: Nahlah
authors.initials: N
authors.lastname: AlGhasham
authors.affiliation: Department of Medicine, King Faisal Specialist Hospital and Research Center, Alfaisal university, Riyadh, Saudi Arabia.
authors.forename: Saad
authors.initials: S
authors.lastname: AlGhamdi
authors.affiliation: Department of Medicine, King Faisal Specialist Hospital and Research Center, Alfaisal university, Riyadh, Saudi Arabia.
authors.forename: Dania
authors.initials: D
authors.lastname: AlKhafaji
authors.affiliation: Department of Medicine, King Faisal Specialist Hospital and Research Center, Alfaisal university, Riyadh, Saudi Arabia.
authors.forename: Bandar
authors.initials: B
authors.lastname: ALAmro
authors.affiliation: Department of Medicine, King Faisal Specialist Hospital and Research Center, Alfaisal university, Riyadh, Saudi Arabia.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Zeitouni
authors.affiliation: Department of Radiology, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
authors.forename: Fawaz
authors.initials: F
authors.lastname: Skaff
authors.affiliation: King Faisal Cancer Centre, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
authors.forename: Hazzaa
authors.initials: H
authors.lastname: AlZahrani
authors.affiliation: King Faisal Cancer Centre, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
authors.forename: Adher
authors.initials: A
authors.lastname: AlSayed
authors.affiliation: Department of Biostatistics, Sidra Medical and Research Center, Doha, Qatar.
authors.forename: Naser
authors.initials: N
authors.lastname: ElKum
authors.affiliation: Department of Medicine, King Faisal Specialist Hospital and Research Center, Alfaisal university, Riyadh, Saudi Arabia.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Moawad
authors.affiliation: Department of Medicine, King Faisal Specialist Hospital and Research Center, Alfaisal university, Riyadh, Saudi Arabia.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Nasmi
authors.affiliation: Department of Medicine, King Faisal Specialist Hospital and Research Center, Alfaisal university, Riyadh, Saudi Arabia.
authors.forename: Mohannad
authors.initials: M
authors.lastname: Hawari
authors.affiliation: Department of Critical Care Medicine, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
authors.forename: Khalid
authors.initials: K
authors.lastname: Maghrabi
keywords: Clinical probability; Deep vein thrombosis; Pulmonary embolism; d-dimer