Doubtful diagnosis

YET another question that nags the scientific community is the health authorities' criterion for classifying a patient "JE positive" because this is an important clue to how an entirely different virus could be mistaken for Japanese encephalitis.

While it was understood that the authorities used the JE IgM enzyme-linked immunosorbent assay (ELISA) method which measures the level of a particular antibody in a person (in this case, JE antibodies), the test is only meaningful if two samples are drawn from the same patient over a period of time.

A memorial service was held in Seremban for the victims of the viral outbreak early this month. Both local and foreign scientists are still wondering about the criteria for determining whether a person is 'JE positive'.

Just finding antibody to a virus in a single serum sample does not confirm anything, says Prof Charles Calisher, a microbiologist at the Colorado State University in the United States, on ProMED (http://www.healthnet.org), an online forum for emerging diseases.

If a second sample is drawn from the same source after a period time, and the sample shows a higher level of antibody, that is a better indicator that a patient has been infected.

Likewise, if the level of antibody in both samples remains low, chances are that the verdict is negative, ot that other verdict is negative, ot that other diagnostic methods like PCR (polymerase chain reaction) or virus isolation should be used.

The need for a paired-sample testing is all the more essential in the present outbreak of viral encephalitis because personnel in the pig farming industry tend to already have JE antibodies in their system.

Having antibodies does not necessarily mean you are ill, or have been infected in the past. Foe example, we all have antibodies against tuberculosis (TB) from our childhood inoculation, but that does not mean that we've had TB in the past, nor are we have having it now.

Besides, it is perfectly normal for those living or working near pig farms to have JE antibodies in them anyway because they are extremely likely to be exposed to the virus which is endemic here. Even the staff of the Veterinary Research Institute in Ipoh, which is located within 2km from pig-farming areas, carry JE antibodies in them.

But to date, it is still unknown whether a single or paired serum sample was used in determining a person's status of JE infection.

Secondly, with the JE vaccination programme implemented by health authorities, it becomes increasingly difficult to tell to tell where the antibody came from - whether it was from the patient's exposure to a wild-type virus, or a result of the vaccine.

The best confirmation is of course the isolation of a virus from the patient. But to date, there has been no report whether such a move has been achieved or even attempted.

When queried why there has been no answer to these questions, especially those posed by experts on ProMED, Health Ministry deputy director of the Disease Control Division Datuk Dr Tee Ah Sian says: "It's of no use discussing the technical aspects of the diagnosis now. Not only is it very technical, we also feel that it is no use to the public, and it may confuse them.

"As for ProMED, it is only visited by a handful of technical people, and not the public."

A comprehensive report will be released when the outbreak is truly over, when things are under control, says Dr Tee.

Fair enough. But with Nipah apparently now detected in Penang and Malacca, the question is, when will it be under control?