Diagnosis of dengue- an overview
Rabindran1, Gedam D. S.2
1Dr. Rabindran, Consultant, Neonatologist, Billroth Hospital, Chennai,
India, 2Dr. D. Sharad Gedam, Professor of Paediatrics, R. K. D. F.
Medical College Associated S. R. K. University, Bhopal, MP,
India.
Address for
Correspondence: Dr. Rabindran, E- mail:
rabindranindia@yahoo.co.in
The first investigation ordered on clinical suspicion of dengue is
complete blood count. The classical dengue triad includes increased
hematocrit, atypical plasmacytoidlymphocytosis and thrombocytopenia
[1]. Hemoconcentration (hematocrit elevated > 45% or by >
20% from previous value) is diagnostic of Dengue Hemorrhagic Fever.
Further confirmation is usually made with Dengue Antigen test. During
early stages of the disease around 4-5 days of fever onset, virus
isolation, nucleic acid or antigen detection are used to diagnose the
virus from serum, plasma or tissues. However serology remains the
method of choice during convalescence. Other tests include antibody
titre for dengue virus types, Polymerase chain reaction (PCR), Liver
function tests, Serum protein & albumin levels &
Coagulation panel.
Lab criteria for dengue diagnosis include any one of the following 4
tests
1) Fourfold change in immunoglobulin G (IgG) or IgM antibody titre to 1
or more dengue virus antigens [2],
2) Tissue dengue virus antigen assay by immunohistochemistry/
immunofluorescence or serum enzyme immunoassay (MAC-ELISA, IgG ELISA,
nonstructural protein 1 [NS1] ELISA, EIA)[1]; MAC-ELISA has 90%
sensitivity & 95% specificity when done 5 days after onset of
fever. Different formats like capture ELISA, capture ultramicroELISA,
dot-ELISA, AuBioDOT IgM capture & dipsticks are available
[3]. Dengue NS1 antigen can be detected as early as first day post onset
of symptoms and remains detectable upto 18 days. Microsphere-based
immunoassays (MIAs) based on covalent bonding of antigen or antibody to
microspheres or beads & detection using lasers to elicit
fluorescence of varying wave lengths is faster than MAC-ELISA. Plaque
Reduction and Neutralization Test (PRNT) & micro neutralization
PRNT are the most specific serological tools for dengue antibody
detection.
3) Viral genomic sequences in tissue, serum or cerebral spinal fluid
(CSF) by reverse-transcriptase PCR (RT-PCR) assay [4]; RT–PCR
has 80-90% sensitivity & more that 95% specificity [3]. Real
time RT-PCR based on TaqMan / SYBR green, NASBA (nucleic acid sequence
based amplification)assay and RT-LAMP are recent advances in molecular
techniques [5] .NASBA assay is an isothermal RNA-specific amplification
assay which includes an initial reverse transcription, RNA
amplification & detection by electrochemiluminescence or
fluorescent-labelled molecular beacon probes [6].
4) Isolation of dengue virus from serumusing Cell culture. The mosquito
cell line C6/36 (cloned from Ae. albopictus) or AP61 (from Ae.
pseudoscutellaris) are the host cells of choice. Mammalian cell
cultures like Vero, LLCMK2, and BHK 21 are less efficient. Continuous
lines of vertebrates, such as VERO, BHK-21, LLC-MK2, inoculation into
animals and mosquitos are also used. The isolated viruses are
detectedby indirect immunofluorescence using monoclonal antibodies
against all four serotypes [7]. However it takes 1–2 weeks.
Characteristic lab findings also include mild- moderate elevation of
aspartate aminotransferase and alanine aminotransferase values [8]. In
severe dengue increased hematocrit, Hypoproteinemia, Prolonged
prothrombin time & activated partial thromboplastin time,
Decreased fibrinogen & Increased amount of fibrin split
products are present. Guaiac testing for occult blood in stool
& hematuria may be present. Imaging studies like Chest
radiography, Head computed tomography (CT) scanning to detect
intracranial bleeding /cerebral edema due to severe dengue,
Ultrasonography to detect ascites, pleural effusion , pericardial
effusion and thickened gallbladder wall may be contributory
[9].
Biosensors is newer technology which is rapid, sensitive, specific,
qualitative & quantitative. Types cDNA, IgM, IgG,
Glycoprotein-E, NS1 protein and viral particles are used as different
analyte probes. Different ofbiosensorsinclude Piezoelectric sensors,
Optical biosensors& Electrochemical biosensors. Electrochemical
impedance spectroscopy monitors changes in capacitance associated with
targets binding to prepared receptive electrode & can be used
for analysis of classical antigen–antibody binding events.A
disposable paper based device known as Made-in-Singapore rapid test kit
detects dengue-specific antibodies from saliva within 20 minutes
& also differentiates between primary and secondary dengue
infection [10]. Ferritin recently has been studied as a marker for
differentiating dengue infection from other febrile illnesses of
infective/ inflammatory etiology even in the absence of a positive NS1
antigen or a positive IgM antibody for dengue [11].
Khandelwal R et al in this issue observed that early febrile period of
dengue fever, majority of patients have normal white blood cell count.
Any change in the values of total leucocyte count points towards the
progression of the disease severity [12].
Since dengue produces a broad spectrum of non-specific symptoms
clinical diagnosis is unreliable. As the disease worsens rapidly prompt
early laboratory confirmation & early intervention may be
life-saving.
Funding:
Nil, Conflict of
interest: None initiated.
Permission from IRB:
Yes
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How to cite this article?
Rabindran, Gedam D. S. Diagnosis of dengue- an overview. Int J Pediatr
Res. 2017;4(10):588-589. doi: 10.17511/ijpr.2017.10.01.