Malaria is usually confirmed by the microscopic examination of blood films or by antigen-based rapid diagnostic tests (RDT). In some areas, RDTs must be able to distinguish whether the malaria symptoms are caused by "Plasmodium falciparum" or by other species of parasites since treatment strategies could differ for non-"P. falciparum" infections. Microscopy is the most commonly used method to detect the malarial parasite—about 165 million blood films were examined for malaria in 2010. Despite its widespread usage, diagnosis by microscopy suffers from two main drawbacks: many settings (especially rural) are not equipped to perform the test, and the accuracy of the results depends on both the skill of the person examining the blood film and the levels of the parasite in the blood. The sensitivity of blood films ranges from 75 to 90% in optimum conditions, to as low as 50%. Commercially available RDTs are often more accurate than blood films at predicting the presence of malaria parasites, but they are widely variable in diagnostic sensitivity and specificity depending on manufacturer, and are unable to tell how many parasites are present. However, incorporating RDTs into the diagnosis of malaria can reduce antimalarial prescription. Although RDT does not improve the health outcomes of those infected with malaria, it also does not lead to worse outcomes when compared to presumptive antimalarial treatment.