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6. Diagnosis of malaria

feasible. Microscopy has further advantages in that it can be used for speciation and
quantification of parasites, and to assess response to antimalarial treatment. Microscopy
can also be used in the identification of other causes of fever. However, a major drawback
of light microscopy is its requirement for well-trained, skilled staff and, usually, an energy
source to power the microscope.

In many areas, malaria patients are treated outside of the formal health services, e.g. in
the community, in the home or by private providers; microscopy is generally not feasible
in many such circumstances, but RDTs may be possible. Although RDTs for detection of
parasite antigen are generally more expensive, their deployment may be considerably cost
effective in many of these settings. The sensitivities and specificities of RDTs are variable,
and their vulnerability to high temperatures and humidity is an important constraint.
Despite these concerns, RDTs make it possible to expand the use of confirmatory
diagnosis. Practical experience and operational evidence of best practices from large-scale
implementation, though still limited, should guide wide-scale deployment of RDTs on
a programmatic level.
In the diagnosis of severe malaria cases, microscopy is a preferred option; it not only
provides the diagnosis of malaria, but it is useful in assessing other important parameters
in a severely ill patient. In situations where an RDT has been used to confirm malaria,
this allows for a rapid institution of antimalarial treatment, however, where possible a
microscopic examination is recommended to enhance the overall management of the
patient.

6.3 Where malaria transmission is low-to-moderate and/or unstable
Parasitological confirmation of the diagnosis of malaria is strongly recommended. This
should be provided by high quality microscopy or, where this is not available, by RDTs.
Low-to-moderate transmission settings include most areas outside Africa. In Africa,
6
this includes many urban areas that have effective malaria control programmes; during
the low-transmission season, it includes areas with seasonal malaria.

In settings where malaria incidence is very low, parasitological diagnosis for all fever
cases may lead to considerable expenditure to detect only a few patients who are actually
suffering from malaria. In such settings, health workers should be trained to identify
patients that may have been exposed to malaria (e.g. recent travel to a malaria endemic
area, or lack of effective preventive measures) and have symptoms that may be attributable
to malaria before they conduct a parasitological test.

6 Transmission intensity is conventionally expressed in terms of EIR (see Section 2). There is as yet no consensus
on criteria for determining the thresholds between high- and low-to-moderate transmission settings. Suggested
criteria include: the proportion of all children under 5 years of age with patent parasitaemia, and the incidence
of individuals with the spleen palpable below the umbilicus in children aged 2–9 years. The IMCI guidelines
recommend that areas in which fewer than 5% of young children with fever have malaria parasitaemia should be
considered as low-transmission settings.
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