Malaria Mistreated in Nearly Two Thirds of Cases in Kenya

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Click Here for Product Infosites – Information from Industry. November 26, 2009 (Washington, DC) — Results from a study conducted in 2 health facilities in Kenya show that the mistreatment of malaria might be as high as 66%. The findings, presented here at the American Society of Tropical Medicine and Hygiene 58th Annual Meeting by Yaw A. Afrane, MB, from the Kenya Medical Research Institute in Kisumu, confirm those from other studies about the mistreatment of malaria in certain regions.

Intensive malaria control programs have been implemented in sub-Saharan Africa; however, the reliability of hospital data on diagnosis and treatment has been questioned.

To determine if or how much misdiagnosis was occurring, Dr. Afrane and colleagues conducted both passive clinic-based and active community-based case surveillance in the communities of Kakamega, Vihega, and Emuhaya. Malaria is endemic in these communities, which are situated in the western highlands of Kenya.

The catchment populations for the passive clinic-based surveillance ranged from 21,000 to 26,085 patients; for the active community-based surveillance, the sampled populations ranged from 1789 to 1954. Mosquitoes, which breed during the wet weather, transmit malaria, so disease prevalence varies by season.

As expected, the active surveillance found a typical peak prevalence of 6% to 7% from May to July, the rainy season, and of 2% to 3% during the nonrainy season. However, when Dr. Afrane put the curve for the passive surveillance pattern against the active one, no seasonality pattern emerged.

"When we saw this discrepancy in the number of cases between one method and another, we wanted to see what was going on," Dr. Afrane said during an interview with Medscape Infectious Diseases. "You wouldn't expect to see a difference with a seasonally occurring disease like malaria." Several factors could explain such a difference, including overtreatment, misdiagnosis, presumptive treatment, and underreporting.

To study this, random blood slides were made from patients referred for malaria testing. Slides were analyzed by Dr. Afrane's research team and by hospital technicians. All readings were done in a masked fashion; readers did not know how the others had interpreted the slides.

Blood slides were obtained from patients who were presumptively treated for malaria because of the symptoms they showed. A questionnaire was designed to collect information from these patients, and clinicians were asked how they made their diagnosis of malaria.

The findings were quite striking, Dr. Afrane said. Among the 2544 outpatients (close to half were children younger than 5 years), 42% were diagnosed with clinical malaria and 85% presented with a fever.

According to Dr. Afrane, clinical malaria is diagnosed by the presence of fever, parasitemia (by microscopy), and other related symptoms, such as vomiting, headache, nausea, and diarrhea. However, microscopy didn't bear these findings out.

Of the 2544 patients, microscopy showed the "true positive" rate to be 35% (n = 914) and the "true negative" rate to be 64% (n = 1630). Among the 914 cases of true positives, the clinic diagnosed 54% as positive. All these subjects received antimalarial treatment.

For the 45.7% diagnosed as negative by the clinic, more than half (57%) received antimalarial treatment. Treatment of the true negatives shed even more light on what was going on, Dr. Afrane explained. Among these 1630 patients, the clinic diagnosed 28% as positive by microscopy. All these patients received antimalarial treatment. Among the nearly 72% that were deemed negative by the clinic, 68% received treatment.

The difficulty lies in the reliability of the microscopy test. "There are several reasons for the unreliability of microscopy," said Meredith McMorrow, MD, MPH, FAAP, from the Centers for Disease Control and Prevention's Malaria Branch in Atlanta, Georgia, and chair of the session. "Limited resources probably play a big role in terms of having good equipment, but high staff turnover and limited opportunities for training may also play a role."

Dr. Afrane agreed that this is a big part of the problem. "Some of the misdiagnosis problems can also come from cases where parasite levels are low, and therefore more difficult to accurately detect," Dr. Afrane told Medscape Infectious Diseases. "So what happens is that clinicians end up not trusting the test and make the decision to treat people based on clinical judgment."

Dr. Afrane and his team also studied data from 784 outpatients who did not receive diagnostic testing at the clinic visit, 37% of whom had a clinical diagnosis of malaria. The reasons for the diagnosis varied; 45% of patients refused testing because of lack of money, fear of having their blood drawn, or believing it wasn't necessary. Physicians did not request laboratory confirmation of malaria in approximately half the cases because they considered it unnecessary.

The Kenyan investigator reported that 63% of patients ended up being overprescribed malaria drugs, mostly artemisinin-combination therapy (ACT). ACT is now considered the best therapy for malaria caused by Plasmodium falciparum.

"There is a very big debate about whether presumptive treatment is or isn't good," said Dr. Afrane. "It's very hard for clinicians to see sick patients and not treat them." This challenge is compounded when a reliable diagnostic test is not available.

However, the misuse of drugs — as demonstrated in this study — always generates concern about the early onset of resistance, Dr. Afrane explained. In addition, the unreliability of hospital-based data makes accurate evaluation of malaria programs difficult.

But there is light on the horizon, he said. Rapid diagnostic tests (RDTs) for malaria detect specific antigens produced by malaria parasites that are present in the blood of infected individuals. Some RDTs also test for the presence of antibodies. "RDTs are being rolled out now for use in settings like this," noted Dr. McMorrow. "There are still some technical challenges, like stability under varying field conditions and educating staff about these new tools, but we think these are very promising in terms of improving diagnostic accuracy."

The study was funding by National Institutes of Health grants. The authors have disclosed no relevant financial relationships.

American Society of Tropical Medicine and Hygiene (ASTMH) 58th Annual Meeting: Abstract 679. Presented November 20, 2009.

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Authors and Disclosures
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Maria Sgambati, MD
Maria Sgambati, MD is a freelancer for Medscape.

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