title: Derivation of a risk assessment model for hospital-acquired venous thrombosis: the NAVAL score.
abstract: Venous thrombosis (VT) is a preventable cause of death in hospitalized patients. The main strategy to decrease VT incidence is timely thromboprophylaxis in at-risk patients. We sought to evaluate the reliability of risk assessment model (RAM) data, the incremental usefulness of additional variables and the modelling of an adjusted score (the NAVAL score). We used the RAM proposed by Caprini for initial assessment. A 5 % systematic sample of data was independently reviewed for reliability. We evaluated the incremental usefulness of six variables for VT during the score modelling by logistic regression. We then assessed the NAVAL score for calibration, reclassification and discrimination performances. We observed 11,091 patients with 37 (0.3 %) VT events. Using the Caprini RAM, high-risk and moderate-risk patients were respectively associated with a 17.4 (95 % confidence interval [CI] 6.1-49.9) and 4.2 (95 % CI 1.6-11.0) increased VT risk compared with low-risk patients. Four independent variables were selected for the NAVAL score: "Age", "Admission clinic", "History of previous VT event" and "History of thrombophilia". The area under the receiver-operating-characteristic curve for the NAVAL score was 0.72 (95 % CI 0.63-0.81). The Net Reclassification Index (NRI) for the NAVAL score compared with the Caprini RAM was -0.1 (95 % CI -0.3 to 0.1; p = 0.28). We conclude that the NAVAL score is a simplified tool for the stratification of VT risk in hospitalized patients. With only four variables, it demonstrated good performance and discrimination, but requires external validation before clinical application. We also confirm that the Caprini RAM can effectively stratify VT risk in hospitalized patients in our population.
authors.affiliation: Instituto de Previdência dos Servidores do Estado de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil. marcosdebastos.hemato@gmail.com.
authors.forename: Marcos
authors.initials: M
authors.lastname: de Bastos
authors.affiliation: Departamento de Medicina Preventiva e Social, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Sandhi M
authors.initials: SM
authors.lastname: Barreto
authors.affiliation: Departamento de Angiologia, Hospital Naval Marcílio Dias, Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: Jackson S
authors.initials: JS
authors.lastname: Caiafa
authors.affiliation: Serviço de Estatística, Departamento de Matemática e Estatística da Pontifícia, Universidade Católica de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Tânia
authors.initials: T
authors.lastname: Boguchi
authors.affiliation: Grupo de Estudos de Medicina Tropical, Pós-Graduação em Ciências da Saúde da Faculdade de Medicina da, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: José Luiz Padilha
authors.initials: JL
authors.lastname: Silva
authors.affiliation: Departamento de Clínica Médica, Faculdade de Medicina, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
authors.forename: Suely M
authors.initials: SM
authors.lastname: Rezende
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D007049:Iatrogenic Disease / Q000453:epidemiology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D018570:Risk Assessment; D020246:Venous Thrombosis / Q000453:epidemiology* / Q000209:etiology
keywords: Hospital; Risk assessment; Thromboprophylaxis; Venous thromboembolism