|Year : 2016 | Volume
| Issue : 2 | Page : 133-134
Diagnostic methodologies for the dengue viral infection
Dost Mohamed Khan
Department of Pathology, Shri Sathya Sai Medical College and Research Institute, Kancheepuram, Tamil Nadu, India
|Date of Web Publication||14-Apr-2016|
Dost Mohamed Khan
Department of Pathology, Shri Sathya Sai Medical College and Research Institute, Ammapettai, Kancheepuram, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Khan DM. Diagnostic methodologies for the dengue viral infection. Int J Health Allied Sci 2016;5:133-4
The dengue infection is a major international public health concern in tropical and subtropical regions as per World Health Organization. A 30-fold rise in dengue infection has been reported worldwide due to a combination of population growth, unplanned urbanization, global warming, increased air travel, lack of efficient mosquito control, and insufficient public healthcare facilities. Humans are the primary host of dengue virus, but it also circulates in nonhuman primates. Dengue infection may be subclinical or symptomatic. Clinical illness occurs in three traditionally recognized forms: Dengue fever; dengue hemorrhagic fever; and dengue shock syndrome.
Efficient and accurate diagnosis of dengue is of primary importance for clinical care (i.e. early detection of dengue infection, case confirmation and differential diagnosis with other infectious diseases), outbreak control, pathogenesis, academic research, vaccine development, surveillance activities, and clinical trials. The methods most commonly used for dengue diagnosis include detection on: (i) Virus in cell culture; (ii) viral nucleic acid; (iii) dengue virus antigens, (iv) specific antibodies raised to them and hematological test (platelet and hematocrit value). Using a combination of two or more of these techniques increases the accuracy of diagnosis. In the early stage, virus isolation, genome detection or antigen identification may each be used for diagnosis. However, after the acute phase, serology is the method of choice to diagnose disease. The demand for rapidity, cost, and availability of appropriate laboratory resources should also be considered in the choice of methodology. Paired serum samples from acute and convalescent phases should be performed by both MAC-ELISA and IgG ELISA to confirm the results. The IgM:IgG ratio is used to discriminate primary and secondary dengue infection. If IgM:IgG ratio is more than 1.2 is considered as a primary infection and the ratio <1.2 is indicative of secondary infection. Newer approach, IgG avidity test has proved to be beneficial in determining primary and secondary dengue infection. Single sample of acute phase serum is required for IgG avidity index. However, this test is currently not readily accessible globally. There are number of commercial test kits that claim rapid detection of anti-dengue IgM and IgG. Unfortunately, these ready-made kits have either been questioned or unknown because proper validation studies have not been performed and the results not made available publically. NS1 antigen plays a major role in the early diagnosis of dengue infection. After the onset of fever until 9 days NS1 dengue antigen can be detected in peripheral blood before the formation of antibodies. In acute primary infection, NS1 antigen rate is higher than in secondary infection. NS1 assays are highly specific for detection and determination of the appropriate dengue serotype. Hence, NS1 antigen assay provides a main-stay for the early diagnosis dengue infection.
There are rapid and considerable improvement in molecular methods of diagnosis; it is considered as the gold standard method of dengue detection. Molecular strategies are looking to replace virus isolation, which is a lengthy and labor-intensive process due to their high sensitivity. The advanced molecular techniques are real-time reverse transcription polymerase chain reaction (RT-PCR) based on TaqMan ® or SYBR green ®, nucleic acid sequence based amplification assay and RT-LAMP, each of which has a high degree of specificity and sensitivity comparable to that of virus isolation. Real-time one-step RT-PCR has become a trend in rapid detection of the dengue virus by genomic sequence. E/M-specific capture IgM and IgG ELISA has become the new standard in antibody diagnosis due to its high degrees of specificity and sensitivity. For serological diagnosis, detection of the NS1 antigen in acute-phase serum samples has shown promising results. Further studies are needed to evaluate its usefulness and to compare it with real-time one-step RT-PCR with respect to its sensitivity and specificity. Detection of NS1 antigen and antibodies specific to it is a novel serological study showing promise for rapid identification. Both these assays should focus on the feasibility of its use in small-scale laboratories and at reduced expense. However, there is a requirement for further evaluation, quality assurance and comparison with the most sensitive methods that is currently available.
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