From the Guidelines
Diagnosing malaria requires a combination of clinical evaluation, laboratory testing, and molecular biology, with the most recent and highest quality study recommending the use of thick and thin blood films, as well as molecular tests such as PCR, for diagnosis 1. The diagnosis of malaria should be considered for any person who has symptoms such as fever, headache, back pain, chills, sweats, myalgia, nausea, vomiting, diarrhea, and cough, and who has traveled to an area in which malaria is endemic 1. Key points to consider in the diagnosis of malaria include:
- Clinical evaluation: a thorough medical history and physical examination should be conducted, focusing on symptoms like fever, headache, and myalgia.
- Laboratory testing: thick and thin blood films should be examined for the presence of Plasmodium parasites, with the thin film providing ideal morphology for species identification 1.
- Molecular biology: molecular tests such as PCR can provide faster identification and are useful in cases where blood films are negative or difficult to obtain 1.
- Repeat testing: repeat blood samples should be drawn 12-24 hours apart, ideally during febrile episodes, if the initial film is negative and malaria is strongly suspected 1. The use of rapid diagnostic tests (RDTs) and molecular tests can aid in the diagnosis of malaria, but should be used in conjunction with clinical evaluation and laboratory testing 1. It is essential to note that the diagnosis and management of malaria in non-endemic countries presents a continuing challenge, and the use of molecular biology and clinical evaluation is crucial in diagnosing and managing adult patients with malaria in these settings 1.
From the Research
Diagnosis of Malaria
The diagnosis of malaria depends on awareness of the diagnosis and performing the correct diagnostic tests 2, 3. The optimum diagnostic procedure is examination of thick and thin blood films by an expert to detect and speciate the malarial parasites.
- The diagnosis cannot be excluded until more than one blood specimen has been examined by an experienced microscopist 2, 3.
- Rapid diagnostic tests (RDTs) which detect plasmodial antigens or enzymes can also be used to diagnose malaria, especially for P. falciparum 2, 3, 4.
- RDTs for other Plasmodium species are not as reliable 2, 3, 4.
- A complete blood count (CBC), hepatic panel, and blood smear should be performed for patients with a history of travel to a malaria-endemic area in the preceding year 5.
- Thrombocytopenia and hyperbilirubinemia each has a positive predictive value of 95% in the presumptive diagnosis of malaria 5.
Challenges in Diagnosing Malaria
- There are no typical clinical features of malaria, even fever is not invariably present 2, 3.
- Malaria in children (and sometimes in adults) may present with misleading symptoms such as gastrointestinal features, sore throat or lower respiratory complaints 2, 3, 5.
- Differentiating between influenza-like illness and malaria can be challenging, especially in patients with a history of travel to a malaria-endemic area 5.