View/Open - TWAS & OWSD Thesis Repository Home

clinical data is useful for epidemiological studies. Ideally, a standard form,containing fill - in spaces for this information may be distributed to potentialcontributors. Samples submitted without the above information on dates of onset andcollection present problems for the laboratories in selecting and interpreting testsand are of little value to the attending physician (Vomdam and Kuno, 1997).2.5.1 DETECTION OF ANTIBODYHistorically, tests to measure antibodies against dengue virus have utilizedbiological markers such as Haemagglutination inhibition, complement fixation andneutralization tests. These are reliable tests for measuring antibodies but they fail todistinguish IgM from IgG antibodies, the former being the best indicator of a recentinfection. For this reason, these tests usually require paired acute and convalescentsamples to make a diagnosis. The recent trend in serologic techniques has beentowards tests such as Enzyme-linked Immunosorbent Assays (ELlSA), in which theantibody isotypes are measured individually, providing a picture of the developingimmune response, which is qualitative as well as quantitative. This is particularlyimportant in those cases in which the diagnostic laboratory receives only a singleserum sample (Vomdam and Kuno, 1997).2.5.2 ISOLATION, DETECTION AND IDENTIFICATION OF VIRUSIsolation of most strains of dengue virus from clinical specimens can beaccomplished in a majority of cases provided the sample is taken in the first fewdays of illness and proceeds without delay (WHO, 2001). Specimens that may besuitable for virus isolation include acute phases serum, plasma and washed buffyfrom the patient, autopsy tissues from fatal cases especially liver, spleen, lymphnodes and thymus, and mosquitoes collected in nature. For the first periods ofstorage (up to 48 hours), specimens to be used for virus isolation can be kept at +4°Cor +8°C. For longer storage, the serum should be separated and frozen at 70°C, andmaintained at such so that thawing does not occur. If isolation from leucocytes is tobe attempted heparinized blood samples should be delivered to the laboratory withina few hours. Whenever possible, original materials (viremic serum or infectedmosquito pools) as well as laboratory -passaged materials should be preserved forfuture study (WHO, 2001). Tissues and pooled mosquitoes are triturated or51