Diagnosis Bill Brieger | 31 Aug 2009 08:53 am
Trusting the Tests
USAID’s Essential Health Services Program in Angola – known as Serviços Essenciais de Saúde (SES) – has been developing sentinel surveillance sites at four locations so far. These have able to document current practices in malaria diagnosis and treatment.
During a regular seminar among representatives of Municipality Health Department staff from Luanda Province in Angola SES raised the issue of Rapid Diagnostic Tests and their value in preventing over-use of expensive artemisinin-based combination therapy (ACT) medicines. We also acknowledged that there were people who trusted their clinical judgement more than RDTs. Similar skeptics were also at our meeting.
We presented data from other countries that showed how clinical diagnosis of malaria resulted in an over-estimation of malaria cases by anywhere from 25% to 75% of the time. This may depend on the age of the patient (more accurate in children below five years of age) and in areas of higher endemicity. But regardless of the context, there were excess cases and wasted treatments when clinical diagnosis was used compared to laboratory diagnosis.
The data so far indicate that a similar problem exists in Angola. Unofficial results show that out of all clinically suspected cases of malaria in the four sentinel clinics only 34% of children below five years of age and 23% of older people had laboratory confirmed malaria parasites. In contrast half of the children below 5 years and two-thirds of the others who were clinically suspected of having malaria were given ACTs, i.e. much more than the numbers with laboratory confirmed malaria.
If people question laboratory tests, what also of RDTs? One of the skeptical people in the room shared that all the RDT tests in their clinic had turned out negative, and based on his clinical experience, he was sure that many of the patients really had malaria. We called attention to a recent study that found very low prevalence in urban Luanda, making it challenging to identify parasites. He was still not convinced.
Finally participants from two other municipalities came to our rescue. They agreed that initially all their results had been negative. Then they undertook training and follow-up supervision of all staff who would use RTDs. This resulted in identification of positive cases. Their stories also confirmed experiences in Tanzania where such training was crucial.
As more countries move closer to elimination and malaria cases become rarer, the importance of correct diagnosis and surveillance will increase. We must ensure not only that our RDTs are of high quality (see FIND Report), but also that those who combat malaria at the front lines have trust in our diagnostic tools.