Dengue Test in Hyderabad - Types, Indications, Cost

The different types of dengue test are broadly classified into the following categories.

• Dengue nucleic acid detection 
• RT-PCR
• Real-time RT-PCR
• Dengue NS1 test (NS1 antigen test) or Non-structural protein1 (NS1) antigen assay 
• Dengue serology test or dengue antibody test
• IgM ELISA test for dengue (dengue IgM test)
• IgG ELISA test for dengue (antibody IgG test)
• IgM/IgG ratio
• IgA ELISA test for dengue
• Haemagglutination-inhibition test
• Dengue blood test
• Complete blood count
• Dengue clinical Assessment
• Tourniquet test dengue 
• Dengue virus isolation

Dengue nucleic acid detection



Nucleic acid detection is a critical technique that allows for detecting certain nucleotide sequences, revealing the presence of a pathogen or the early onset of a sick condition. 

• RT-PCR: Reverse transcription-polymerase chain reaction (RT-PCR) has a faster turnaround time and higher sensitivity compared to virus isolation. Extraction and purification of nucleic acid, amplification of nucleic acid, and detection and characterisation of the amplified product are the three fundamental processes of RT-PCR.
  
  The method used to amplify or detect the PCR products and the method applied for subtyping depend on the area of the genome targeted by the primers, and the sensitivity of the RT-PCR procedures can range from 80% to 100% when compared to virus isolation.
  
  
• Real-time RT-PCR: Using primer probes and pairs that are specific to each dengue serotype, the real-time RT-PCR test can quantitatively measure viral RNA in a single step. A fluorescent probe is used to detect reaction products in real-time within a customised PCR machine.
  
  
• Dengue NS1 test or Non-structural protein1 (NS1) antigen assay: Dengue NS1 antigen tests detect the dengue virus's non-structural protein NS1. During a dengue infection, this protein is secreted into the bloodstream. In the acute phase of dengue virus infections, NS1 is detectable. During the first 0-7 days of symptoms, NS1 testing can be as sensitive as molecular tests. NS1 testing is not advised after day 7. This is also known as the dengue NS1 ELISA test when NS1 is detected based on ELISA with real-time polymerase chain reaction.
  
  NS1 antigen is a glycoprotein that is synthesised by all flaviviruses and secreted from infected mammalian cells during the acute phase of infection. This dengue antigen test analysis is consistent, showing a fairly high sensitivity and extremely high specificity to dengue infection. Some research studies are evident for higher sensitivity for NS1 antigen detection in primary infection (> 90%) than in secondary infection (60–80%). High NS1 antigen levels were also shown to be associated with greater viraemia levels, suggesting that they may serve as a potential marker for serious sickness. The dengue ns1 antigen range varies from 0.5-2 μg/ml in acute phase and <0.04 μg/ml in convalescent phase samples.
  

Dengue serology test or dengue antibody test

• IgM ELISA test for dengue: This is also known as MAC-ELISA (Immunoglobulin M antibody-capture enzyme-linked immunosorbent assay) or dengue IgM test. One to four serotypes of dengue-specific antigens (DEN-1, -2, -3, and -4) are adhered to captured anti-dengue IgM antibodies. These antibodies are detected by monoclonal or polyclonal dengue antibodies that, conjugated (directly or indirectly) with an enzyme, change a non-coloured substrate into coloured products, which is further measured by a spectrophotometer.
  
  Immunoglobulin M can be detected with serum, blood on filter paper, or saliva samples, which are collected more or equal to 5 days after the onset of fever. MAC-ELISA has been reported with good sensitivity and specificity if the test is performed more than five days after the onset of fever.

• IgG ELISA test for dengue: This test is used to detect recent or prior dengue infections where similar antigens are employed, as in the MAC-ELISA. IgG antibodies can be detected up to 10 months after infection using an E/M-specific capture ELISA (GAC). A fourfold or more increase in IgG antibodies of dengue virus infections in acute and convalescent paired sera can be used to detect the recent infection; however, IgG antibodies are lifelong as evaluated by E/M antigen-coated indirect IgG ELISA.
  
  This technique allows for the detection of IgG antibodies in serum, plasma, and blood samples preserved on filter paper and can be used to determine the presence of primary or secondary dengue infection. The IgG ELISA test lacks specificity with flavivirus serocomplex groups.

• IgM/IgG ratio: Primary and secondary dengue viral agents can be distinguished by measuring a virus E/M protein-specific IgM/IgG ratio where the IgM capture ELISAs and IgG capture ELISA tests are the most widely used tests. The ratio greater than 1.2- 1.4 indicates primary infection, whereas lesser than 1.2- 1.4 indicates secondary infection.

• IgA ELISA test for dengue: Serum anti-dengue IgA is typically detected one day after IgM using anti-dengue viral IgA capture ELISA (AAC-ELISA). Around day eight following fever onset, the IgA titre reaches its highest point and then rapidly declines until it is undetectable by day 40.

• Haemagglutination-inhibition test: The capacity of dengue antigens to agglutinate RBC is the basis of the haemagglutination-inhibition test. The serum containing anti-dengue antibodies inhibits the agglutination process, which is measured in an HI test. The response to a primary infection is defined by the low level of antibodies in the acute-phase blood collected before day 5 and a steady elevation of HI antibody titres subsequently. During secondary dengue infections, HI antibody titres grow fast, generally exceeding 1:1280.

Dengue blood test

CBC test for dengue: Dengue fever is manifested by a decrease in White Blood Cells (WBC) < 5000 cells/mm3 count (leukopenia), platelet count (thrombocytopenia)< 150,000 cells/mm3 and an increase in haematocrit value (5-10%) with no evidence of plasma leakage.

In the case of Dengue Hemorrhagic Fever (DHF), there is evidence of plasma leakage, which is evident of ascites or pleural effusion. The dengue blood test report reveals the clinical diagnostic parameters of dengue infection, such as a decrease in platelet count <100,000 cells/mm3 and an increase in haematocrit greater than 20 %. Occasionally, a decrease in platelet counts below 100,000 cells/mm3 may be detected in dengue fever, but it is usually always observed in DHF.

Dengue clinical assessment

Tourniquet test dengue: The dengue fever tourniquet test is a kind of physical examination that can identify and stratify dengue sickness. Infection with dengue virus may result in enhanced capillary permeability, where the tourniquet test exploits by providing persistent pressure to these tiny capillaries. This results in the development of petechiae, which are pinpoint, non-raised, purplish-red patches on the skin in patients with dengue hemorrhagic fever (DHF) and dengue fever.

The tourniquet test dengue procedure includes inflating a blood pressure cuff midway on the upper arm of the patient between the systolic and diastolic blood pressure. After five minutes, there will be the formation of petechiae; if the number of petechiae counted in an area surpasses a specified quantity (greater or equal to 20 petechiae in one square-inch region), then the test result is considered a positive tourniquet test in dengue fever.

Dengue virus isolation

Virus isolation specimens should be collected early in the infection, during the period of viraemia (usually before day 5). The virus can be recovered from serum, plasma, and peripheral blood mononuclear cells, and it can also be collected at autopsy. The collected specimens will be kept between +4 °C and +8 °C for storage for up to 24 hours. -70 °C in a deep freezer or liquid nitrogen storage is recommended for longer storage.

Rapid diagnostic test for dengue

Dengue rapid test is being utilised more frequently to confirm recent dengue infections due to its short turnaround time for results and ease of use. The dengue rapid test result provides rapid and accurate confirmation of recent dengue infections.



The clinical characterisation of dengue infection depends on factors such as the age and the host's immunological and underlying medical condition. A precise laboratory diagnosis of recent dengue infection is critical since a delay in detection raises severe dengue risk and could lead to a poor disease outcome. The traditional diagnostic test for dengue can be performed via virus isolation, immunological-based assays, or polymerase chain reaction (molecular-based). However, these approaches are costly, require special equipments and have a significant turnaround time. Therefore, dengue rapid diagnostic tests (RDTs) are developed to detect IgM antibodies, dengue NS1 antigen, and IgG antibodies in whole blood, serum, or plasma. The results of these RDTs, which are based on the immunochromatographic approach, can be achieved in less than 30 minutes.

Differences between ELISA and RDT