Value of Routine Dengue Diagnostic Tests in Urine and Saliva Specimens

Abstract

Background: Dengue laboratory diagnosis is essentially based on detection of the virus, its components or antibodies directed against the virus in blood samples. Blood, however, may be difficult to draw in some patients, especially in children, and sampling during outbreak investigations or epidemiological studies may face logistical challenges or limited compliance to invasive procedures from subjects. The aim of this study was to assess the possibility of using saliva and urine samples instead of blood for dengue diagnosis.

Methodology/principal findings: Serial plasma, urine and saliva samples were collected at several time-points between the day of admission to hospital until three months after the onset of fever in children with confirmed dengue disease. Quantitative RT-PCR, NS1 antigen capture and ELISA serology for anti-DENV antibody (IgG, IgM and IgA) detection were performed in parallel on the three body fluids. RT-PCR and NS1 tests demonstrated an overall sensitivity of 85.4%/63.4%, 41.6%/14.5% and 39%/28.3%, in plasma, urine and saliva specimens, respectively. When urine and saliva samples were collected at the same time-points and tested concurrently, the diagnostic sensitivity of RNA and NS1 detection assays was 69.1% and 34.4%, respectively. IgG/IgA detection assays had an overall sensitivity of 54.4%/37.4%, 38.5%/26.8% and 52.9%/28.6% in plasma, urine and saliva specimens, respectively. IgM were detected in 38.1% and 36% of the plasma and saliva samples but never in urine.

Conclusions: Although the performances of the different diagnostic methods were not as good in saliva and urine as in plasma specimens, the results obtained by qRT-PCR and by anti-DENV antibody ELISA could well justify the use of these two body fluids to detect dengue infection in situations when the collection of blood specimens is not possible.

Fig 1. Detection of DENV RNA by qRT-PCR in plasma, urine and saliva specimens.

Percentage of plasma, urine and saliva specimens that tested positive for DENV RNA, by day of sampling after onset of fever. (n = 144 patients for plasma, 118 for urine and 144 for saliva).

Fig 2. Mean viral load measured by qRT-PCR in plasma, urine and saliva.

Fig 3. Positivity rates of NS1 protein detection in plasma, urine and saliva.

Percentage of samples that tested positive for NS1 protein by capture ELISA in urine, saliva and plasma, by day of sampling after onset of fever (n = 193, 197 and 217 patients with a confirmed dengue infection included for NS1 detection in urine, saliva and plasma, respectively).

Fig 4. Detection of anti-DENV antibodies in plasma, urine and saliva.

Percentage of samples that tested positive by MAC-ELISA (A), AAC-ELISA (B) and IgG indirect ELISA (C) in urine, saliva and plasma samples according to time after onset of fever (D for day, W for week and M for month).

Fig 5. Partial dependence plots for the most influential variables explaining viral genome detection in plasma, urine and saliva.

Fig 6. Partial dependence plots for the most influential variables explaining NS1 antigen detection in plasma, urine and saliva.

Fig 7. Partial dependence plots for the most influential variables explaining anti-DENV antibodies detection in plasma, urine and saliva.