From the Guidelines
The best test for acute malaria is microscopy examination of thick and thin blood films.
Key Points
- This method is considered the gold standard for diagnosing malaria because it allows for the detection of parasites, identification of the species involved, quantification of parasitemia, and differentiation between sexual and asexual forms 1.
- Microscopy examination requires skilled and continuously trained personnel, which can be a challenge for most microbiology laboratories in non-endemic countries 1.
- Rapid diagnostic tests (RDTs), such as those using loop-mediated isothermal amplification (LAMP), are also useful for initial screening, especially in settings where reliable blood films are not readily available 1.
- Nucleic acid amplification tests (NAATs), such as PCR, are highly sensitive and can be used to confirm infection, assist in species identification, and differentiate between malaria and Babesia 1.
- Serology plays a limited role in the diagnosis of acute malaria, as antibodies may not appear early in infection and titers may be too low to determine the status of infection 1.
Diagnostic Approaches
- Microscopy examination of thick and thin blood films should be performed as soon as possible, ideally within 1 hour of blood collection 1.
- RDTs can be used for initial screening, but positive results should be confirmed by microscopy examination of blood films 1.
- NAATs can be used to confirm infection and assist in species identification, but may not be readily available in all settings 1.
Important Considerations
- Malaria diagnosis should be considered a stat test, and results should be reported as soon as possible to guide treatment decisions 1.
- Clinical and epidemiologic information should be considered when interpreting test results, and additional testing may be required to confirm the diagnosis 1.
From the Research
Diagnostic Methods for Acute Malaria
The best test for acute malaria is a subject of ongoing research and debate. According to 2, microscopy remains the gold standard for diagnosing malaria, but it has limitations. Rapid diagnostic tests (RDTs) have expanded the ability to diagnose malaria due to their simplicity and low cost, but they lack sensitivity and specificity.
Comparison of Diagnostic Methods
A study published in 3 compared five methods of malaria detection in the outpatient setting, including conventional microscopy, the quantitative buffy coat (QBC) technique, acridine orange staining, and the ParaSight-F test. The results showed that the ParaSight-F test had the highest level of agreement with conventional microscopy, followed by Field stain.
Advantages and Disadvantages of Diagnostic Methods
The advantages and disadvantages of commonly used diagnostic methods are discussed in 4. Microscopic examination of thick and thin blood films remains the gold standard, but rapid antigen tests and nucleic acid amplification methods may also play a useful role in detection of acute infection. However, RDTs have limitations, including lack of sensitivity and specificity, as reported in 2 and 5.
Recent Developments in Malaria Diagnostics
Recent advances in malaria RDT technology have increased demand for low-cost, easy-to-use assays in areas endemic for malaria, as reported in 5. Substantial developments in diagnostic sensitivity and specificity, improvements in non-falciparum RDTs, and novel biotechnological innovations are gradually aligning the performance of RDTs with reference-level diagnostics, including PCR and expert microscopy gold standards.
Key Points
- Microscopy remains the gold standard for diagnosing malaria, but it has limitations 2
- RDTs have expanded the ability to diagnose malaria due to their simplicity and low cost, but they lack sensitivity and specificity 2, 5
- The ParaSight-F test had the highest level of agreement with conventional microscopy in a comparative study 3
- Recent advances in malaria RDT technology have increased demand for low-cost, easy-to-use assays in areas endemic for malaria 5