<prompt> Most sensitive diagnostic test for dengue is:IgM ELISAComplement fixation testReverse transcriptase PCRElectron microscopy  <response>: Ans. is c i.e., RT - PCRRef: Ananthanarayan, 9the, p. 523 and 7the, p. 137; Harper, 27the, p. 604 Reverse transcriptase PCR RT - PCR based methods are available for rapid identification and serotyping of dengue virus in acute phase serum, roughly during the period of fever. Isolation of the virus is difficult. Neutralizing and Hemagglutination inhibiting antibodies appear within a week after the onset of dengue fever. Analysis of paired acute and convalescent sera to show a significant rise in antibody titer is the most reliable evidence of an active dengue infection. 