title: Is the activated partial thromboplastin time suitable to screen for von Willebrand factor deficiencies?
abstract: The diagnostic approach to von Willebrand factor deficiencies is challenging and requires discretionary use of laboratory resources. Although extensive preoperative testing is not recommended, the activated partial thromboplastin time may be useful, especially in selected categories of patients. To establish the diagnostic sensitivity of this test to identify isolate von Willebrand factor deficiencies, 204 consecutive patients underwent a routine preoperative screening consisting of activated partial thromboplastin time, von Willebrand factor antigen, intrinsic pathway clotting factors activity, lupus anticoagulants and thrombin time. Thirty-seven patients were diagnosed with haemostasis disturbances other than von Willebrand factor deficiencies and were excluded from the evaluation. Isolated von Willebrand factor deficiency was diagnosed in 11 of the remaining 167 patients. A significant correlation was observed between von Willebrand factor antigen and activated partial thromboplastin time. Receiver operating characteristic curve analysis showed an area under the curve of 0.982 (95% confidence interval: 0.972-0.992; P < 0.001). At the 1.17 upper limit of the activated partial thromboplastin time, sensitivity and specificity were 100 and 85%, respectively, with negative and positive predictive values of 100 and 31%, respectively. These results demonstrate that activated partial thromboplastin time has an excellent diagnostic sensitivity and a satisfactory specificity for identifying isolated von Willebrand factor deficiencies.
authors.affiliation: Sezione di Chimica e Microscopia Clinica, Dipartimento di Scienze Morfologico-Biomediche, Università degli Studi di Verona, Ospedale Policlinico G.B. Rossi, Piazzale Scuro 10, 37134 Verona, Italy. ulippi@tin.it
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lippi
authors.forename: Massimo
authors.initials: M
authors.lastname: Franchini
authors.forename: Giovanni
authors.initials: G
authors.lastname: Poli
authors.forename: Gian Luca
authors.initials: GL
authors.lastname: Salvagno
authors.forename: Martina
authors.initials: M
authors.lastname: Montagnana
authors.forename: Gian Cesare
authors.initials: GC
authors.lastname: Guidi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016063:Blood Loss, Surgical / Q000517:prevention & control; D002648:Child; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011300:Preoperative Care / Q000379:methods; D012680:Sensitivity and Specificity; D014842:von Willebrand Diseases / Q000097:blood / Q000175:diagnosis*; D014841:von Willebrand Factor / Q000032:analysis*
chemical_list: D014841:von Willebrand Factor