| Abstract|| |
Background: Dengue an endemic disease in most subtropical and tropical regions of the world is causing severe epidemics in India. An alarming rise of dengue has also been seen in Mumbai, during the recent years. Aim and Objective: The study was conducted to know the prevalence of dengue infection, based on laboratory rapid screening tests for IgM and IgG antibodies and the confirmatory IgM ELISA test and to study the seasonal variation and the clinical profile in these cases. Material and Method: A retrospective study of laboratory test results and clinical profile of suspected dengue cases was carried out in a tertiary care hospital over a period between January 2004 and November 2007. Result: Of the 3 677 samples processed by rapid test for antibodies against dengue (Denguchek), 503 (13.67%) gave positive results. Fifty-six samples (26.41%) were positive by IgM Enzyme linked immunosorbent assay (ELISA) test, of 212 rapid positive samples processed by ELISA test. Our study comprised of 315 adult and 188 pediatric cases. The common symptom of dengue was fever, icterus, myalgia, and headache. Thrombocytopenia (platelet counts <75 000/cmm) was seen in 386 (76.74%) cases. Seventy-seven cases (15.30%) positive by rapid screening tests for dengue antibodies were also positive for IgM/IgG antibodies against Leptospira by Dridot test (Rapid test). Of these, 49 (63.64%) were confirmed to be positive for dengue antibodies by the ELISA test. Conclusion: As dengue causes increased morbidity and mortality and requires prompt diagnosis and treatment for the proper management of these cases, the rapid screening test for IgM/IgG antibodies helps clinicians toward achieving this goal.
Keywords: Dengue, clinical profile, Dengue IgM ELISA
|How to cite this article:|
Turbadkar D, Ramchandran A, Mathur M, Gaikwad S. Laboratory and clinical profile of dengue: A study from Mumbai. Ann Trop Med Public Health 2012;5:20-3
|How to cite this URL:|
Turbadkar D, Ramchandran A, Mathur M, Gaikwad S. Laboratory and clinical profile of dengue: A study from Mumbai. Ann Trop Med Public Health [serial online] 2012 [cited 2018 Aug 15];5:20-3. Available from: http://www.atmph.org/text.asp?2012/5/1/20/92873
| Introduction|| |
Dengue viruses are mosquito-borne flaviviruses that have plagued people for centuries.  Dengue fever has emerged as a serious international public health threat with almost half of the world's population at risk for infection. Although first reports of major epidemics of an illness thought to possibly be dengue occurred on three continents (Asia, Africa, and North America) in 1779 and 1780, reports of illnesses clinically compatible with dengue fever occurred even earlier. Outbreaks of illness in the French West Indies in 1635 and in Panama in 1699 could also have been dengue.  Dengue hemorrhagic fever, the potentially fatal form of dengue virus infection, became generally recognized only in the 1950s following outbreaks in the Philippines and Thailand.  Periodic epidemics have occurred in the Western Hemisphere for over 200 years.  It is estimated that 2.5 billion people are at risk for dengue infection, of which nearly 100 million people contract dengue fever annually and over 250 000 progress to Dengue Hemorrhage Shock (DHF)/ dengue Shock Syndrome (DSS). 
The disease is also endemic in many parts of India, especially the metropolitan cities and towns. Outbreaks are now reported quite frequently from different parts of the country like rural areas of Haryana, Maharashtra, and Karnataka. Till date, more than 80 outbreaks have been reported from 16 States/Union Territories, the largest one being in 1996, when a severe outbreak of dengue/DHF occurred in Delhi, wherein about 10 252 cases and 453 deaths were reported. 
At present, information on adult dengue infections in South Asia is quite limited. Thus, the necessity of this study is to learn the prevalence of dengue infection based on laboratory screening rapid tests for IgM and IgG antibodies and the confirmatory IgM ELISA test; and to study the seasonal variation and the clinical profile in these cases.
| Materials and Methods|| |
A retrospective study was carried out in a tertiary care hospital over a period of 3 years and 11 months (January 2004 to November 2007).
The clinical profile consisting of symptoms like fever, abdominal pain, icterus, myalgia, headache, etc., were analyzed.
Platelet counts were noted in these cases and the results were grouped as counts < 20 000/cmm, > 20 000/cmm to 50 000/cmm, > 50 000/cmm to 75 000/cmm, and >75 000/cmm.
Sera samples were collected from all individuals suspected to be having dengue infection based on their presenting signs and symptoms.
Serological testing was carried out using the Denguchek kit supplied by Zephyr. This is a rapid test, able to detect the presence of IgM as well as IgG antibodies. The sensitivity as well as the specificity is reported to be approximately 100%. All the tests were performed as per the kit manual.
The samples testing positive for IgM antibodies by the rapid test were processed by the confirmatory IgM Capture ELISA kit supplied by Panbio. This kit is reported to have a sensitivity of 92% and a specificity of 97%.
The samples testing positive for IgM antibodies by the rapid test were also tested to look for the presence of IgM/IgG antibodies against leptospirosis by the Leptospira Dridot kit (Biomerieux) with a reported sensitivity of 91.2% and a specificity of 91.0%.
The suspected cases and the positive samples were studied month wise to know the seasonal pattern of the disease.
| Results|| |
A total of 3 677 samples were collected from suspected individuals, based on their presenting complaints. These were processed by rapid test for antibodies against dengue (Denguchek test performed as per the kit manual). Of all, 503 (13.67%) gave positive results. Of these 503 samples, 212 could be tested by the confirmatory IgM ELISA test and 56 samples (26.41%) were found to be positive [Table 1].
Our study comprised of 315 adult and 188 pediatric cases.
The peak incidence of positivity each year was seen between July and November [Figure 1].
Fever was the major presenting complaint in all these cases. The other common presenting symptoms in these suspected cases of dengue were icterus in 25.8%, myalgia in 25.0%, and headache in 13.9% [Figure 2].
Thrombocytopenia (platelet counts <75 000/cmm) were seen in 76.74% (386) cases. Sixty-eight cases (17.6%) had counts below 20 000/cmm, 241 (62.4%) had counts between >20 000 and 50 000/cmm, and 77 (19.9%) had counts between >50 000 and 75 000/cmm [Figure 3].
Clinical parameters like hypotension, oliguria, pleural effusion, polyserositis, etc., were seen in 36.18% of all IgM-positive (by Rapid test) patients.
The samples positive by rapid screening tests for dengue antibodies were also tested for IgM/IgG antibodies against leptospirosis by Dridot test (Rapid screening test for leptospirosis). Of them, 77 cases (15.30%) were found to be positive for both. All of these were subjected to IgM ELISA test for dengue antibodies and 49 (63.64%) were confirmed to be exclusively positive for dengue antibodies by the ELISA test [Table 2].
| Discussion|| |
The present retrospective study of 3 677 clinically suspected cases of dengue was done in tertiary care hospital. These patients came with various complaints like fever, myalgia, headache, fever, vomiting, abdominal pain, etc. Some gave history of bleeding episodes like epistaxis, rash over the body, gum bleeds, etc.
Of all the samples processed by rapid test for antibodies against dengue (Denguchek test performed as per the kit manual), 503 (13.67%) gave positive results [Table 1]. These were positive either for IgM Antibodies alone--288 (57.25%) patients, indicating a primary infection or for both IgM and IgG antibodies--107 (21.27%) patients, indicating a secondary infection (107). Cases with a positive result for IgG antibodies alone were not considered as they are indicative of past infection and seldom progress to any complications. On the other hand, these could be fever from causes other than dengue.
Of these 503 samples positive by rapid screening test, 212 could be tested by the confirmatory IgM ELISA test as per the kit instructions and 56 samples (26.41%) were found to be positive [Table 1]. IgM capture ELISA is considered to be a confirmatory test. The remaining 281 cases might have given a false-positive test to cross-reacting antibodies.
Our study comprised of 315 adult and 188 pediatric cases. This shows that the trend of dengue in Mumbai is shifting toward the adults. This is in accordance with reports from elsewhere. ,
We studied the monthly distribution of the suspected cases as well as the positive cases (by Rapid test). We saw that the peak incidence for each of the groups was between July and November [Figure 1] this is due to the increased mosquito breeding toward the later part of monsoon as well as the post-monsoon period. 
Fever was the major presenting complaint in all these cases (100%). The other common presenting symptoms in these suspected cases of dengue were icterus in 25.8%, myalgia in 25.0%, and headache in 13.9% [Figure 2]. These features in one sense are quite misleading, since they could be the manifesting symptoms for a host of other diseases like leptospirosis, malaria, etc. Thus, microbiological diagnostic tests along with hematological and biochemical parameters help the clinician in the proper management of patients.
Thrombocytopenia (platelet counts <75000/cmm) were seen in 386 cases (76.74%). Sixty-eight cases (17.6%) had counts below 20000/cmm, 241 (62.4%) had counts between >20000/cmm and 50000/cmm, and 77 (19.9%) had counts between >50000/cmm and 75 000/cmm [Figure 3].
Clinical parameters like hypotension, oliguria, pleural effusion, polyserositis, etc., were seen in 182 (36.18%) of all IgM-positive (by Rapid test) patients. The majority of these cases were found to be of a milder nature. Although > 50 million cases of dengue fever are estimated to occur each year, a large proportion of infections are asymptomatic.  Evidence of vascular leakage due to increased capillary permeability characterizes and differentiates dengue hemorrhagic fever. 
The samples positive by rapid screening tests for dengue antibodies were also tested for IgM/IgG antibodies against leptospirosis by Dridot test (Rapid screening test for leptospirosis). Seventy-seven cases (15.30%) were found to be positive for both [Table 2]. All of these were subjected to IgM Capture ELISA test for dengue antibodies and 49 (63.64%) were confirmed to be exclusively positive for dengue antibodies by the ELISA test. Because of the protean manifestations, it is of utmost importance to diagnose the disease with great specificity. Thus, IgM Capture ELISA, the confirmatory test rules out the false-positive cases as detected in the Rapid screening test due to the presence of cross-reacting antibodies.
These results suggest that a combination of clinical picture, hematological parameters (thrombocytopenia), and presence of IgM antibodies could be used as supportive markers for the early diagnosis of dengue infection, which will go a long way in the proper management of the cases.
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Department of Microbiology, LTMMC and LTGH, Sion, Mumbai 400 022
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2]