“Laboratory Parameters in Clinically Suspected Dengue Cases in Tertiary Care Teaching Hospital in North Maharashtra”

Background: Dengue an arbovirus infection, has significantly increased in past decade causing increased mortality & morbidity in temperate countries including India. Earlier diagnosis helps in prompt treatment resulting in decrease in mortality & prevention of complications. In present study we have evaluated laboratory parameters for diagnosis along with different demographic profile for prevention of disease. Methods: All clinically suspected patients tested for NS1Ag & IgM by ELISA along with platelet count & Peripheral blood smear. Individual results were used in comparative analysis according to demographic (gender, age) and laboratory (platelet counts, NS1 Ag & IgM) profiles Result: Total serologically confirmed cases were 583( 21.12%) . Lower platelet counts was the most important factors in predicting dengue infection. Furthermore, all demographic and laboratory profiles presented a conservative temporal pattern throughout this long-lasting outbreak. Conclusion: As consistency throughout the epidemic facilitated defining the conservation pattern throughout the early stages, this was useful for improving management during the remaining period. Also NS1 Ag is early & reliable test.


Introduction
Dengue an important emerging disease of tropical & sub tropical region is a Vector born disease is caused by Dengue Virus belonging to the family Flaviviridae & genus Flavivirus. Globally dengue is most important mosquito born viral disease presenting with varied clinical symptoms ranging from flue like fever to deadlier DHF & Shock. (1).
Epidemiologically, globally 50 million people are infected with dengue virus every year while 2 & half billions are at risk of infection 2 . Similarly in India with population of more than 1 billion, it is estimated that India has largest number of dengue cases, with about 33 millions apparent & another 100 million asymptomatic infections occurring annually. 3 The first epidemic of clinical dengue-like illness was recorded in Madras (now Chennai) in 1780 and the first virologically proved epidemic of DF in India occurred in Calcutta and Eastern Coast of India in 1963-1964 . 4/5/6. The first major wide spread epidemics of DHF/DSS occurred in India in 1996 involving areas around Delhi 7 and Lucknow 8 and then it spread to all over the country 9 India has documented infections from all four serotypes.
According to WHO , the incidence of dengue globally has shot up 30 folds in last 50 yrs. The cumulative dengue diseases burden has attained an unprecedented proportion in recent times with a sharp increase in the size of population at risk. Dengue disease presents highly complex pathophysiological, economic & ecological problem 10 Currently neither effective antiviral agents to treat dengue infection nor an effective vaccine are available. So main approach for prevention, control & management of dengue lays with vector control & early diagnosis of disease.
In current study, we have studied different parameters like seasonal variations, gender, age along with laboratory parameters in relation with clinical symptoms which will help us to determine burden of disease in this region & preventive measures to be taken. Sporadic cases were noted throughout year. ( Figure 1)

Materials and Methods
Out of 2755 serum samples tested, 583 (21.16%)were positive for either one or both serological marker. Of these 583 sample 378( 64.8%) were exclusively positive for NS1 antigen while 167( 28.6%) sample showed IgM antibody titer positivity. 38 serum samples were positive for both serological marker i.e. NS1 antigen & IgM antibody (Table 2) Among 583 sero-positive cases thrombocytopenia (Platelets <1 Lac) was evident in 299 (51.29%) while out of 2172 seronegative cases thrombocytopenia was seen in 159(7.3%) Out of the 378 NS1 positive cases, 224( 59.26%) had platelet count less than 100,000/ml while out of 167 IgM positive samples, 83(49.7%) had thrombocytopenia. (Table 3 &   Before the advent of NS1 Ag testing, demonstration of dengue specific IgM /Ig G antibodies was mainstay for diagnosis of dengue infection since viral culture or detection of viral genome by molecular method is not feasible at grass root level. As antibodies begin to appear on 5 th day of fever in primary & 3 rd day in secondary infection, diagnosis is delayed due to lag period in this test.

4)
In contrast NS1 Ag is detectable in blood from day 1 of fever & can be seen up to 9 day even when viral RNA detection is negative by RT PCR. 22

Conclusion
The present study shows that dengue infection is more common in young adult age group favoring males as this group more involved in outdoor activities, which exposes them to mosquitoes. Since monsoon in our region in not heavy & has intermittent showers, peak of case is seen during mid & end of monsoon. For all febrile patients with thrombocytopenia, Dengue NS1 Ag, IgM antibodies detection should be done as low platelet is important but not exclusive test for this infectious disease.