Simple Blood Test Helps to Differentiate Dengue Fever From SARS

30 September 2004
By Corinne Purtill

Researchers in Singapore have found that a routine blood test can determine within hours whether a patient is sick with dengue fever or severe acute respiratory syndrome, two illnesses with deceptively similar symptoms but vastly different consequences.

The finding highlights the challenge for doctors facing an unknown epidemic, be it SARS or avian influenza, to distinguish a new enemy by eliminating familiar ones.
Singaporean doctors have realized that a simple test of a patient's platelet count can screen out those infected with SARS from those with dengue, according to the Straits Times as reported by Deutsche Presse-Agentur.

Though both diseases start with persistent high fevers and muscle aches, people with dengue have significantly fewer platelets in their blood, DPA reported Tuesday. Platelets are the particles that help blood to clot.

"The full blood count test is a simple and well-established laboratory test, and can be done in an hour or two," said Dr Chng Wee Joo of the National University Hospital, as quoted by The Straits Times.

The platelet count is only a screening mechanism; the quickest diagnostic test for SARS isn't effective until the patient's third day of symptoms, DPA said.
Dengue fever is so common in Cambodia that doctors here were quick to rule it out as a cause of suspected SARS patients' symptoms last year.

Dengue can be diagnosed almost immediately using the same simple platelet test that Singaporean doctors said they will now use for SARS screening, said Dr Rathi Guhadasan, medical education coordinator at Angkor Hospital for Children in Siem Reap, on Wednesday.

There were no confirmed cases of SARS in Cambodia during last year's scare. Of the 28 suspected SARS cases tested at the Pasteur Institute, three or four patients were found to be suffering from AIDS and one from a typhoid-like illness, said Dr Jean Baptiste Dufourcq of Calmette Hospital. None of the possible SARS patients were diagnosed with dengue, he said.

"Dengue fever is for us a very common disease, so it is a routine examination," Dufourcq said Wednesday.

SARS stumped doctors as it spread across Asia last year, sending health workers scrambling to diagnose patients by ruling out familiar conditions with similar symptoms.

That and other lessons learned from the SARS scare are still in practice as Cambodia confronts other public health threats such as bird flu, said Dr Ly Sovann, head of the Ministry of Health's surveillance bureau.

Health workers and others in areas where bird flu has been found have been vaccinated for simple flu, in order to rule that disease out if they get sick.
Testing equipment and personal protective gear stocked up in anticipation of a SARS outbreak here is now on reserve in case bird flu crosses over to humans, he said.