Symptoms of change: malaria diagnosis in areas of low prevalence

Malaria is a major health problem in the developing world and the situation is getting worse as malaria parasites become increasingly drug-resistant. Accurate diagnosis is essential for targeting new treatments and conserving resources. Could clinical assessment of symptoms replace microscopy in malaria diagnosis?

Researchers from the London School of Hygiene and Tropical Medicine and the Indian Government Medical College report on a study of malaria symptoms in Surat, India. They found that no symptom or combination of symptoms consistently indicates malaria infection. They conclude that there is no alternative to microscopy for diagnosis in areas where malaria levels are low.

Early diagnosis and prompt treatment of malaria are essential. But areas with high levels of malaria often have scarce healthcare resources. Health workers may not have access to sophisticated methods for diagnosis. In the past, they overcame this by routinely giving chloroquine, the most common antimalarial treatment, to any patient with fever. But as resistance to cholorquine spreads, new drugs are used which are more expensive and have greater side-effects. So the need for accurate diagnosis is increasing.

Is reliable malaria diagnosis possible using a simple assessment of patients' symptoms? There are no universal criteria for symptomatic diagnosis of malaria. For example, in Thailand, fever and headache without a cough are accurate predictors of malaria in children. In the Philippines, the symptoms that most consistently predict malaria are fever, chills and sweating. Symptoms are influenced by the level of malaria in the area. In addition, perception of symptoms may be culturally determined.

Could symptoms be used to diagnose malaria in a region where malaria incidence is relatively low? The researchers studied data from 1945 children and 2885 adults who attended an outpatient fever clinic in Surat City, India. Blood samples were examined microscopically and patients' symptoms were assessed. The results show that:

• None of the symptoms or signs are sensitive or specific enough to be used individually for diagnosis.
• Combinations of several symptoms used for diagnosis in other areas are not useful for this group of patients. This is because there are many common causes of fever among this population.

The researchers highlight several implications of the findings:

• Chloroquine resistance is low in India and sulfadoxine/pyremethamine is less effective for Plasmodium vivax malaria. So chloroquine should be the first-line drug of choice in this country.
• Although symptomatic diagnosis of malaria may have some potential in highly endemic areas of Africa, it could have dangerous consequences in areas such as Surat where malaria incidence is lower.
• There is currently no good alternative to accurate microscopy for diagnosis of malaria in areas where the prevalence is low.

Source(s):
'A clinical algorithm for the diagnosis of malaria: results of an evaluation in an area of low endemicity' by D. Chandramohan et al., Tropical Medicine and International Health 6 (2001)

Funded by: UK Department for International Development

id21 Research Highlight: 11 December 2001

Further Information:
Daniel Chandramohan
Department of Infectious and Tropical Diseases
London School of Hygiene and Tropical Medicine
Keppel Street
London WC1E 7HT
UK

Tel: +44 (0)20 7927 2322
Fax: +44 (0)20 7580 9075
Contact the contributor: d.chandramohan@lshtm.ac.uk

London School of Hygiene and Tropical Medicine, UK

Other related links:
The Malaria Foundation has information on many malaria-related issues, including research, plus a forum for discussion.

Check the Roll Back Malaria site for the latest news and information on this WHO initiative.

Look at the issue of International Health Matters on malaria.

The Multilateral Initiative on Malaria is an international collaboration for scientific research into malaria.

This issue of the WHO Bulletin has many research articles on malaria.