The meanings of misdiagnosis

In Mali, ‘shocking levels’ of malaria misdiagnosis are being reported. “The discrepancy between real and assumed cases has reached “shocking” levels all over Africa … Malaria diagnostics in Mali rely on expensive equipment which most health clinics, particularly in rural areas, cannot afford and do not have the trained staff to use … As a result most doctors “make assumptions based on suspicion,” he said, leading to over-treatment of malaria cases … most people who develop a fever in Mali do not visit a health clinic at all either because they live too far away, or are unwilling to pay up to US$0.95 for a consultation.”

They self diagnose and treat instead.” IRIN reports that, “Up to 70 percent of cases of feverish illness in children are diagnosed and treated at home.” In contrast, “Laboratories the gold standard. Mali needs more and better-equipped laboratories to combat mass misdiagnosis.”

Although the news release about Mali does not give numbers, they may be quite substantial. Two years ago a medical officer working for a major corporation in Nigeria discussed the experiences from their company’s employee/family clinics and showed that without laboratory tests at least 75% of patients whom clinicians diagnosed as having malaria were free of parasites. The company thought that lab tests resulted in a major savings for the company in terms of malaria pharmaceuticals.

Many diseases present with malaria-like symptoms, including dengue fever, which is poorly recognized in Africa. Nordstrand et al. (2007) report that in the absence of laboratory diagnosis, tickborne relapsing fever is treated as malaria in Togo.

dscn8366.JPGThere are concerns about the cost of laboratory diagnosis. Rapid Diagnostic Tests (RDTs), though not without expense, are a solution in low resource settings. Hopkins et al. (2008) report that “Based on the high PPV (positive predictive value: 93%) and NPV (negative predictive value: >97%), HRP2(histidine-rich protein 2)-based RDTs are likely to be the best diagnostic choice for areas with medium-to-high malaria transmission rates in Africa.”

Even when laboratory diagnosis is available, it may not be used. As Polage and colleagues observed in Ghana, “Perhaps the most significant barrier to laboratory use was physicians’ reliance on clinical judgment.”

A lesson here is that clinical diagnosis may be no better that self-diagnosis. An interesting question is by how much would the world’s burden of malaria be reduced simply by performing an accurate diagnosis in a laboratory or with RDTs?

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