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), their 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 compared.
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 programme.
An effective quality management system for malaria microscopy requires:
- Central coordinator(s) to oversee quality assurance
- 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
More than 204 million patients tested by microscopic examination in 2016
The number of patients tested by microscopic examination increased to more than 204 million in 2016. The global total is dominated by India, which accounted for almost 125 million slide examinations. In the African Region, the number of patients examined by microscopy increased from 33 million in 2010 to 51 million in 2016.
- Bench aids for malaria microscopy
Basic malaria microscopy – Part I: Learner's guide. Second edition
Basic malaria microscopy – Part II: Tutor's guide. Second edition
- Malaria microscopy quality assurance manual – Ver. 2
- The microscopic diagnosis of malaria
- Universal access to malaria diagnostic testing – An operational manual