Clinical probability score and D-dimer estimation lack utility in the diagnosis of childhood pulmonary embolism.

BACKGROUND: Childhood 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/
METHODS: This 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.
RESULTS: PE 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.
CONCLUSIONS: The 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.