17th June 2024

Investigation and Management

Thick blood films are used to determine whether parasites are present, whereas thin blood films are used to determine the species and level of parasitaemia. Rapid detection strips can be used to detect species-specific antigens. Three negative antigen tests are generally needed before malaria is ruled out. Antigen tests may be less reliable in areas of high endemicity and patients are, therefore, sometimes treated on clinical suspicion.

Criteria for severe falciparum is detailed in the table below. This is assuming that no other obvious causes are present to explain the clinical and laboratory findings. The criteria are similar for the other species of malaria, with further detail available in the referenced World Health Organization guidelines. The parasitaemia threshold for severe malaria may change if the patient has not had a previous malaria infection. Malaria severity score is a very simple single best answer question to create and so it is worth being familiar with the criteria before the MRCP exam.

Severe malaria, regardless of species, is managed with IV artesunate, with non-severe malaria usually managed with artemisinin combination therapy. IV quinine was previously the treatment of choice for severe malaria, however there may be a mortality benefit of using artesunate over quinine, as well as a reduction in adverse side-effects such as tinnitus, deafness, and hypoglycaemia. IV artesunate treatment can lead to a delayed haemolysis presentation in the days to weeks after treatment. It is, therefore, important to follow these patients up over this time period. Malaria in pregnancy is slightly more complicated, with guidance available in the referenced UK and World Health Organization documents. As mentioned previously, primaquine is necessary to clear the hypnozoite stage of P. ovale and P. vivax. This can cause haemolysis in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency and so this condition should be screened for before commencing eradication therapy.

Adapted from: https://www.who.int/publications/i/item/guidelines-for-malaria