title: Optimisation of the diagnostic strategy for suspected deep-vein thrombosis in primary care.
abstract: Recently, a diagnostic score was developed to safely exclude deep-vein thrombosis (DVT) in primary care. A large prospective study, in which general practitioners used this diagnostic score to decide which patients needed referral, revealed that the number of referrals for ultrasound measurements was reduced by almost 50%, at the cost of an acceptably low risk (1.4%, 95% confidence interval [CI] 0.6% to 2.9%) of venous thromboembolic events in non-referred patients. However, simple adjustments to the diagnostic score (so-called updating) might further improve the accuracy; i.e. reduce the proportion of missed diagnoses (safety) or increase the proportion of patients who do not need to be referred (efficiency). We applied two updating methods to determine whether adjusting the weights of the predictors or adding new predictors could further improve the accuracy of the diagnostic score. The weights of the predictors did not need to be adjusted, but inclusion of 'history of DVT' and 'prolonged travelling' significantly added predictive value (p-values 0.014 and 0.023, respectively). However, adding these predictors to the diagnostic score did not improve the safety and efficiency: at equal safety (1.4% missed diagnoses among the non-referred patients), the efficiency was lower (43.5%, 95% CI 40.4% to 46.6% compared to 49.4%, 95% CI 46.3% to 52.5%). The diagnostic score for excluding DVT in primary care has good accuracy in its original form and could not be improved by including additional predictors. This suggests that the original diagnostic score can be used to safely exclude clinically suspected DVT in primary care.
authors.affiliation: Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Utrecht, The Netherlands. K.J.M.Janssen@umcutrecht.nl
authors.forename: Kristel J M
authors.initials: KJ
authors.lastname: Janssen
authors.forename: Eit F
authors.initials: EF
authors.lastname: van der Velde
authors.forename: Arina J
authors.initials: AJ
authors.lastname: Ten Cate
authors.forename: Martin H
authors.initials: MH
authors.lastname: Prins
authors.forename: Henk C P M
authors.initials: HC
authors.lastname: van Weert
authors.forename: H E Jelle H
authors.initials: HE
authors.lastname: Stoffers
authors.forename: Harry R
authors.initials: HR
authors.lastname: Büller
authors.forename: Ruud
authors.initials: R
authors.lastname: Oudega
authors.forename: Arno W
authors.initials: AW
authors.lastname: Hoes
authors.forename: Diane B
authors.initials: DB
authors.lastname: Toll
authors.forename: Karel G M
authors.initials: KG
authors.lastname: Moons
mesh_terms: D003661:Decision Support Techniques; D003936:Diagnosis, Computer-Assisted / Q000379:methods* / Q000592:standards; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008487:Medical History Taking; D008875:Middle Aged; D011320:Primary Health Care / Q000379:methods; D018570:Risk Assessment; D014195:Travel; D014463:Ultrasonography; D020246:Venous Thrombosis / Q000175:diagnosis* / Q000000981:diagnostic imaging