What tests needed for diagnosing dengue?

Suspecting dengue, members of a Sivaram Krishna family took him to a private hospital in Hyderabad where doctors prescribed an NS1 antigen test. The rapid test was negative in a few hours and the family members were relieved. However, Sivaram Krishna’s condition continued to deteriorate and he was on the verge of dengue shock syndrome, before doctors began to relaunch it.

What went wrong with the diagnosis of Sivaram Krishna? Why did your condition worsen when the tests confirmed that you did not have dengue? The reason is that Sivaram Krishna underwent NS1 testing after five days of the appearance of dengue-like symptoms. Senior doctors in Hyderabad said patients and their loved ones should be aware of the type of tests available in the market to confirm dengue.

Public hospitals at Fever Hospital, Gandhi and Osmania General OGH offer IgM-based tests performed by the Institute of Preventive Medicine (IPM). Although this is the case, private hospitals in Hyderabad and elsewhere in the state of Telangana use NS1 rapid antigen kits to test patients for confirmation of dengue.

“Patients should understand that NS1 antigen tests should be performed only during the first part of the dengue infection, which is usually within the first five days of the onset of clinical symptoms.” After five days, IgM-ELISA antibody tests must be performed and confirmed. If a patient undergoes an NS1 test within the first five days, the chances of diagnosing dengue are better, but there will be times when the results are false negatives and positives, “explains Superintendent, Fever Hosptial, K. Shankar.

Physicians specify that if the NS1 rapid test is performed after five days of symptom onset, the test results may be false. There is also a tendency among physicians to prescribe NS1 antigen tests to satisfy patients, since most of them are reluctant or unwilling to wait more than six days for IgM testing. “Instead of depending or wasting time waiting for the test results, doctors should start treating the patient based on their symptoms when they get sick,” say doctors.

As of August, the number of reported cases of dengue in the district of Hyderabad was 79 and in the first 18 months of September the number reached 70. In general, health authorities reported that between January and September, 200 cases of dengue and one death in Hyderabad.

To strengthen the surveillance program, authorities urged private hospitals to send samples to test dengue in the MPI. “After collecting samples for the initial tests, we asked private hospitals to collect and send a second set of samples to confirm the IPM,” said District Health and Health Officer (HO) P. Venkteshwar Rao.