WHO recommends prompt parasite-based diagnosis by microscopy or malaria rapid diagnostic test (RDT) in all patients suspected of malaria before antimalarial treatment is administered. Light microscopy entails visualization of the malaria parasites in a thick or thin smear of the patient’s blood.
Types of microscopy
Malaria microscopy allows the identification of different malaria-causing parasites (P. falciparum, P. vivax, P. malariae and P. ovale), various parasite stages, including gametocytes, and the quantification of parasite density to monitor response to treatment. Microscopy is the method of choice for the investigation of malaria treatment failures. Giemsa is the classical stain used for malaria microscopy, and diagnosis requires examination of both thin and thick films from the same patient. Light microscopy is the diagnostic standard against which other diagnostic methods have traditionally been measured.
Quality assurance of microscopy-based diagnosis
While microscopy remains the mainstay of parasite-based diagnosis in most large health clinics and hospitals, the quality of microscopy-based diagnosis is frequently inadequate for ensuring good sensitivity and specificity of malaria diagnosis, adversely affecting health outcomes and optimal use of resources.
An acceptable microscopy service is one that is both cost-effective and provides results that are consistently accurate and sufficiently timely to have a direct impact on treatment. This requires a comprehensive and functioning quality assurance (QA) programme.
An effective quality management system for malaria microscopy requires:
- Central coordinator(s) to oversee QA
- A reference (core) group of microscopists at the head, supported by an external quality assurance programme, and with expertise in training and slide validation
- Good training systems in place based on competency relevant to clinical settings
- Regular retraining and assessment/grading of competency, supported by a validated reference slide set (malaria slide bank)
- A sustainable slide validation system that detects gross inadequacies with good feed-back and a system to address inadequate performance
- Good supervision at all levels
- Good supply management and maintenance of microscopes
- Clear standard operating procedures (SOPs) at all levels
- An adequate budget as part of funding for malaria case management
188 million patients tested by microscopic examination in 2012
The number of patients tested by microscopic examination increased to a peak of 188 million in 2012. The global total is dominated by India, which accounted for over 120 million slide examinations in 2012. The number of patients examined by microscopy remains relatively low in the African Region, although it has increased over the last four years.
Last updated: 25 March 2014
- Technical consultation to update the WHO Malaria microscopy quality assurance manual (2014)
- Universal access to malaria diagnostic testing: an operational manual (2011)
Basic malaria microscopy (2010)
Basic malaria microscopy (2010)
- The microscopic diagnosis of malaria – CD-ROM (2009)
- Malaria microscopy quality assurance manual (2009)
- Bench aids for malaria microscopy (2009)