|LETTER TO EDITOR
|Year : 2015 | Volume
| Issue : 2 | Page : 126-127
Diagnostic dilemmas in the detection of dengue specific immunoglobulin M by different kits
Poongodi Lakshmi Santhana Kumarasamy, Revathy Chinnachamy, Nepoleon Rajamani
Department of Microbiology, Tirunelveli Medical College, Tirunelveli, Tamil Nadu, India
|Date of Web Publication||14-May-2015|
Poongodi Lakshmi Santhana Kumarasamy
Department of Microbiology, Tirunelveli Medical College, Tirunelveli - 627 011, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Kumarasamy PL, Chinnachamy R, Rajamani N. Diagnostic dilemmas in the detection of dengue specific immunoglobulin M by different kits. J Sci Soc 2015;42:126-7
|How to cite this URL:|
Kumarasamy PL, Chinnachamy R, Rajamani N. Diagnostic dilemmas in the detection of dengue specific immunoglobulin M by different kits. J Sci Soc [serial online] 2015 [cited 2020 Aug 7];42:126-7. Available from: http://www.jscisociety.com/text.asp?2015/42/2/126/157053
Dengue has been a recurrent phenomenon in Southern districts of Tamil Nadu and is caused by the antigenically related four serotypes of dengue virus. Primary infections are usually uneventful, immunity is type specific. In endemic areas, secondary infections are common resulting in explosive outbreaks of more severe and lethal dengue hemorrhagic fever and dengue shock syndrome. Dengue infection presents with nonspecific symptoms, mimics other febrile illness. Hence, laboratory testing remains a mainstay in the diagnosis. Simultaneous detection of NS1, immunoglobulin M (IgM), immunoglobulin G (IgG) is essential to distinguish primary and secondary infection because each marker appears in different period. They can be detected separately by enzyme-linked immunosorbent assay (ELISA) and simultaneously by the rapid immunochromatography testing. NS1 is a highly conserved glycoprotein essential for viral replication can be detected from day 1 up to day 9-18 after the onset of illness.  NS1 is detected for a short period in the secondary infection because IgG may serve to mask or rapid clearance in the form of immune complexes.  IgM is more specific, appears only after 3-5 days of illness in primary infection and persist for 8 months, in the secondary infection it is not always positive.  IgG appears in primary infection at moderate levels by 14 th day and persist for life, in the secondary infection it rises within 1-2 days of onset of infection. NS1 does not show marked cross reactions with other arboviral diseases, as reported with IgM and IgG. 
Immunoglobulin M capture ELISA is the only available diagnostic test in most of the tertiary care hospitals whereas in primary care level it is being diagnosed clinically. Though virus isolation and reverse transcription-polymerase chain reaction are considered as gold standard method in the diagnosis, they are expensive, not widely available, takes 6-10 days for multiplication. The level of viremia differs greatly, can be detected for 4-5 days, and depends on the time after onset, the antibody titer, strain of the infecting virus, viral genome can be detected until day 8. 
This study was done in Tirunelveli, to analyze the diagnostic dilemmas in the detection of dengue specific IgM by different kits. A total of 185 serum samples were collected from patients with suspected dengue infection and tested for IgM with two different kits National Institute of Virology (NIV) DEN IgM capture ELISA (NIV, Pune, Maharashtra, India) and Panbio ELISA (Inverness Medical Innovations Australian Pty Ltd, Australia). Though it is not optimized to screen general population by these methods, a total of 25 samples collected from normal healthy afebrile patients were also included. Of the 185 samples, 58(31%) were positive by Panbio. By NIV DEN IgM, only 23(12%) were positive, they were positive by Panbio also. Hence, Panbio kit detected 35 samples additionally. Among the normal healthy afebrile patients, seven were positive by Panbio, and none were positive by NIV DEN IgM. Samples negative by Panbio were also negative by NIV DEN IgM [Table 1]. Sensitivity and specificity are claimed as 98.53% and 98.84%, respectively, for NIV DEN IgM. Sensitivity is 94.7% for primary infection and 55.7% for secondary infection, and specificity is 100% as claimed by Panbio. In the present study, Panbio kit is highly sensitive when compared to NIV kit. All these serological assays should be compared with the gold standard tests such as culture or molecular method, which is not done in the present study.
Hence, detection of IgM in a single specimen is merely indicative of a recent dengue infection, should not be interpreted as confirmation of diagnosis without a paired second serum sample. Most of the private hospitals use commercial ELISA kits, sensitivity vary with different assays during primary and secondary infection which mislead the real epidemiology. Further, other factors such as virus strain, host response, day of specimen collection also influence the result. Hence, a rapid, sensitive point of care test detecting NS1, IgM and IgG simultaneously at field level is the need of the day.
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