• T T Biss, L R Brandão, W H A Kahr, A K C Chan, and S Williams.
• Department of Hematology/Oncology, The Hospital for Sick Children, Toronto, ON M5G 1X8, Canada.
• J. Thromb. Haemost. 2009 Oct 1;7(10):1633-8.

BackgroundChildhood pulmonary embolism (PE) causes significant mortality and evidence suggests that it is under-diagnosed. Clinical probability scores and D-dimer estimation to assess pre-test probability have not been studied in children with suspected PE.Patients/MethodsThis retrospective cohort study evaluated Wells simplified probability score for PE in 50 children with PE and 25 PE negative control patients, and D-dimer values in 27 PE positive and 12 PE negative children.ResultsPE positive and PE negative groups had similar rates of risk factors for venous thromboembolism (VTE). Wells simplified probability score showed a small difference between PE positive and PE negative children (median score: PE positive, 4.5; PE negative, 4; P = 0.009), children with PE are more likely to obtain a 'PE likely' score (score > 4), P = 0.012. The difference was of slightly greater significance when the Wells score was adjusted to account for pediatric normal ranges for heart rate, P = 0.007, and signs/symptoms of upper limb DVT, P = 0.006. Children with PE were as likely as PE negative patients to have a D-dimer value within the normal range (PE positive, 15%; PE negative, 25%; P = 0.654). A combination of a 'PE unlikely' score and normal D-dimer value occurred in 1/12 (8%) of PE negative children.ConclusionsThe Wells clinical probability score and D-dimer estimation may lack utility in the determination of pre-test probability of PE in children. Validation of a pediatric clinical probability score, incorporating D-dimer estimation, by prospective study, would be difficult as a result of the rarity of childhood PE.

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