Predictive diagnostic value of the tourniquet test for the diagnosis of dengue infection in adults.

Mayfong Mayxay,Valy Keolouangkhot,Soulignasack Thongpaseuth,Vilada Chansamouth,Catrin E Moore,Michel Strobel,Syho Sisouphone,Rattanaphone Phetsouvanh,Simmaly Phongmany,Thaksinaporn Thaojaikong,Manivanh Vongsouvath,Pankham Vongphachanh,Paul N Newton

doi:10.1111/j.1365-3156.2010.02641.x

Abstract

ObjectiveTo examine the accuracy of the admission tourniquet test in the diagnosis of dengue infection among Lao adults.MethodsProspective assessment of the predictive diagnostic value of the tourniquet test for the diagnosis of dengue infection, as defined by IgM, IgG and NS1 ELISAs (Panbio Ltd, Australia), among Lao adult inpatients with clinically suspected dengue infection.ResultsOf 234 patients with clinically suspected dengue infection on admission, 73% were serologically confirmed to have dengue, while 64 patients with negative dengue serology were diagnosed as having scrub typhus (39%), murine typhus (11%), undetermined typhus (12%), Japanese encephalitis virus (5%), undetermined flavivirus (5%) and typhoid fever (3%); 25% had no identifiable aetiology. The tourniquet test was positive in 29.1% (95% CI = 23.2–34.9%) of all patients and in 34.1% (95% CI = 27.0–41.2%) of dengue-seropositive patients, in 32.7% (95% CI = 23.5–41.8) of those with dengue fever and in 36.4% (95% CI = 24.7–48.0) of those with dengue haemorrhagic fever. Interobserver agreement for the tourniquet test was 90.2% (95% CI = 86.4–94.0) (Kappa = 0.76). Using ELISAs as the diagnostic gold standard, the sensitivity of the tourniquet test was 33.5–34%; its specificity was 84–91%. The positive and negative predictive values were 85–90% and 32.5–34%, respectively.ConclusionsThe admission tourniquet test has low sensitivity and adds relatively little value to the diagnosis of dengue among Lao adult inpatients with suspected dengue. Although a positive tourniquet test suggests dengue and that treatment of alternative diagnoses may not be needed, a negative test result does not exclude dengue.

Highlights

Dengue infection is an increasing public health problem in tropical and subtropical countries, with an estimated 36 million symptomatic cases globally each year and 2.1 million severe dengue cases (Anonymous 2010)
Dengue infection has conventionally been classified into three grades of severity – dengue fever (DF), dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) (WHO 1997) or more recently as dengue, dengue with warning signs and severe dengue (WHO 2009)
The dengue tourniquet test was performed according to the standardized method (WHO 1997) within 24 h of admission by one study team member (MM) while the patient lay on a bed

Summary

Introduction

Dengue infection is an increasing public health problem in tropical and subtropical countries, with an estimated 36 million symptomatic cases globally each year and 2.1 million severe dengue cases (Anonymous 2010). Dengue infection has conventionally been classified into three grades of severity – dengue fever (DF), dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) (WHO 1997) or more recently as dengue, dengue with warning signs and severe dengue (WHO 2009). DHF is caused by increased vascular permeability and may progress to hypovolaemic shock and potentially lethal DSS (WHO 1997). The laboratory diagnosis of dengue is usually based on serological ELISA tests, which detect specific IgM or IgG antibodies and ⁄ or NS1 antigen during the acute phase of infection or a fourfold rise in antibody titre in paired sera. These methods are not commonly available in many dengue-endemic countries. Clinical diagnosis of DSS is usually straightforward, DF and DHF can be a 2010 Blackwell Publishing Ltd

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