Many doctors still confused about dengue diagnosis

2 more test negative under new method.

LAHORE: The Health Department is yet to publicise new guidelines for detecting dengue at the city’s public hospitals, leading to widespread confusion among doctors about the correct procedure for diagnosing the disease.

The experts in the government committee on dengue have recommended the NS-1 test, which detects a specific antigen; the RT-PCR test, which detects the viral RNA; and the micro-haematocrit test, which measures the volume of red blood cells in the blood and is used to diagnose dengue haemorrhagic fever.

However, guidelines for these tests have yet to be displayed at public hospitals and many doctors, speaking to The Express Tribune, admitted they did not know about them. There is also confusion about the accuracy of a diagnostic method widely used to detect dengue last year involving the detection of Immunoglobulin G (IgG) and Immunoglobulin M (IgM), two types of antibodies produced in the blood.

So far this year, 30 people have tested positive for dengue using the IgG and IgM tests, and headlines last week warned of the return of the disease. But the patients later underwent NS-1 tests which turned up negative. Two patients said to be suffering from dengue were tested on Sunday, and both tested negative for the NS-1 antigen, said Mayo Hospital Medical Superintendent Dr Zahid Pervaiz.

“It’s true that so far no diagnostic guidelines have been put up at wards in public hospitals but meetings are taking place and doctors are being informed about the NS-1 test and RT-PCR,” said Dr Pervaiz.

He said it was not clear what was wrong with the patients who tested positive for the IgG and IgM antibodies. “They might have a new virus which we haven’t come across before,” said Prof Irshad Hussain, head of the general medicine department at Mayo Hospital. “This can be confirmed through virus cultures but we don’t have the facility right now.”

Prof Hussain said that general physicians should send patients with classical dengue symptoms (high fever, shivering, joint and muscle pain, rash) to teaching hospitals for the RT-PCR or NS-1 tests. “The NS-1 test results come back after just two or three days,” he said.

GP Dr Mahmood Hasan said he didn’t know what an NS-1 test was. “There should be proper guidelines for diagnosis and they should be published to avoid confusion among doctors and patients. Most doctors rely on the IgG and IgM tests.” Dr Salman Kazmi of the Pakistan Medical Association (PMA) suggested that the government launch a website on the latest diagnostic methods of dengue. “All doctors should be given access to that website using their PMDC registration number. The website should have been launched last year and all the training sessions should be uploaded on the website.”

Health Secretary Captain (retired) Arif Nadeem said that the department was currently focusing on preventive measures. “We have formed high-dependency units for dengue patients but so far not a single diagnosis has been confirmed,” he said.

He said the NS-1 test was required for those who were bitten by the dengue mosquito last year but didn’t suffer any symptoms. They had antibodies to the disease, so their IgG and IgM tests could be positive even if they had not been infected again.

“We have the facility to conduct these tests and we will enhance it when needed,” he said, adding that he was confident there would be fewer infections this year than last.

Published in The Express Tribune, March 5^th, 2012.