title: Utility of the tourniquet test and the white blood cell count to differentiate dengue among acute febrile illnesses in the emergency room.
abstract: Dengue often presents with non-specific clinical signs, and given the current paucity of accurate, rapid diagnostic laboratory tests, identifying easily obtainable bedside markers of dengue remains a priority. Previous studies in febrile Asian children have suggested that the combination of a positive tourniquet test (TT) and leucopenia can distinguish dengue from other febrile illnesses, but little data exists on the usefulness of these tests in adults or in the Americas. We evaluated the diagnostic accuracy of the TT and leucopenia (white blood cell count <5000/mm(3)) in identifying dengue as part of an acute febrile illness (AFI) surveillance study conducted in the Emergency Department of Saint Luke's Hospital in Ponce, Puerto Rico. From September to December 2009, 284 patients presenting to the ED with fever for 2-7 days and no identified source were enrolled. Participants were tested for influenza, dengue, leptospirosis and enteroviruses. Thirty-three (12%) patients were confirmed as having dengue; 2 had dengue co-infection with influenza and leptospirosis, respectively. An infectious etiology was determined for 141 others (136 influenza, 3 enterovirus, 2 urinary tract infections), and 110 patients had no infectious etiology identified. Fifty-two percent of laboratory-positive dengue cases had a positive TT versus 18% of patients without dengue (P<0.001), 87% of dengue cases compared to 28% of non-dengue cases had leucopenia (P<0.001). The presence of either a positive TT or leucopenia correctly identified 94% of dengue patients. The specificity and positive predictive values of these tests was significantly higher in the subset of patients without pandemic influenza A H1N1, suggesting improved discriminatory performance of these tests in the absence of concurrent dengue and influenza outbreaks. However, even during simultaneous AFI outbreaks, the absence of leucopenia combined with a negative tourniquet test may be useful to rule out dengue.
authors.affiliation: Dengue Branch, Division of Vector-Borne Diseases, Centers For Disease Control and Prevention, San Juan, Puerto Rico. hgk4@cdc.gov
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Gregory
authors.forename: Olga D
authors.initials: OD
authors.lastname: Lorenzi
authors.forename: Lisandra
authors.initials: L
authors.lastname: Colón
authors.forename: Arleene Sepúlveda
authors.initials: AS
authors.lastname: García
authors.forename: Luis M
authors.initials: LM
authors.lastname: Santiago
authors.forename: Ramón Cruz
authors.initials: RC
authors.lastname: Rivera
authors.forename: Liv Jossette Cuyar
authors.initials: LJ
authors.lastname: Bermúdez
authors.forename: Fernando Ortiz
authors.initials: FO
authors.lastname: Báez
authors.forename: Delanor Vázquez
authors.initials: DV
authors.lastname: Aponte
authors.forename: Kay M
authors.initials: KM
authors.lastname: Tomashek
authors.forename: Jorge
authors.initials: J
authors.lastname: Gutierrez
authors.forename: Luisa
authors.initials: L
authors.lastname: Alvarado
mesh_terms: D000293:Adolescent; D000328:Adult; D002198:Capillary Fragility; D002648:Child; D003715:Dengue / Q000097:blood* / Q000175:diagnosis* / Q000453:epidemiology; D003716:Dengue Virus / Q000302:isolation & purification; D003937:Diagnosis, Differential; D004636:Emergency Service, Hospital; D058872:Epidemics; D005334:Fever / Q000097:blood / Q000453:epidemiology / Q000821:virology*; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification; D007251:Influenza, Human / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology; D007958:Leukocyte Count; D007970:Leukopenia / Q000097:blood / Q000453:epidemiology / Q000821:virology*; D016133:Polymerase Chain Reaction; D011237:Predictive Value of Tests; D011647:Puerto Rico / Q000453:epidemiology