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Guidelines for the treatment of malaria – 2 edition

It is considered to be the “field standard” against which the sensitivity and specificity of
other methods must be assessed. A skilled microscopist is able to detect asexual parasites
at densities of fewer than 10 per μl of blood, but under typical field conditions the limit
of sensitivity is approximately 100 parasites per μl (8). Light microscopy has important
advantages:
• low direct costs, if the infrastructure to maintain the service is available,
• high sensitivity, if the quality of microscopy is high,
• differentiation between plasmodia species,
• determination of parasite densities,
• ability to monitor response to therapy,
• ability to be used to diagnose many other conditions.

It can be difficult to maintain good quality of microscopy, for various reasons: the need
for adequate training and supervision of laboratory staff; the need to rely on electricity;
delays in providing results to patients; and the need to maintain quality assurance and
control of laboratory services.
Numerous attempts have been made to improve malaria microscopy, but none has proven
to be superior to the classical method of Giemsa-staining and oil-immersion microscopy
for performance in typical health-care settings (9).

a5.3 rapid diagnostic tests
Rapid diagnostic tests are immunochromatographic tests that detect parasite-specific
antigens in a finger-prick blood sample. Some tests detect only one species (P. falciparum),
others detect one or more of the other species of human malaria parasites (P. vivax,
P. malariae and P. ovale) (10–12). They are available commercially in different formats, e.g.
dipsticks, cassettes or cards. Cassettes and cards are easier to use in difficult conditions
outside health facilities.
Rapid diagnostic tests are relatively simple to perform and to interpret, and they do not
require electricity or special equipment. WHO recommends that such tests should have a
sensitivity of > 95% in detecting plasmodia at densities of more than 100 parasites per µl
of blood. WHO maintains a list of RDT manufacturers with ISO 13485:2003 certification
as evidence of quality of manufacture, and it evaluates performance of commercially-
available tests.
Current tests are based on the detection of histidine-rich protein 2 (HRP2), which
are specific for P. falciparum, pan-specific or species-specific Plasmodium lactate
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