Preferred Sample Type

Malarial Parasites Investigation (Blood films and Rapid Diagnostic Test)

Suitable Specimen Types

EDTA Whole Blood

Malarial Parasites Investigation (Blood films and Rapid Diagnostic Test)

Specimen Volume

3mL

Specimen Transport

Standard transport to laboratory

Sample Preparation

None

Turnaround Time

24 hours, if urgent by prior arrangement with laboratory

Sample Stability

4°C for 24 hours

General Information

Microscopy and antigen detection for malarial parasites can be performed on the same sample as the FBC sample. Please supply details of which countries the patient has visited along with prophylaxis or treatment details.

All malaria requests now incorporate the malaria antigen test in addition to microscopy.ails.

Notes

Blood Film

Blood films are stained at pH7.2 and stained with Giemsa and are viewed for the presence of malarial parasites.

WHO guidelines suggest three negative microscopy and antigen detectio. results in 72 hours to exclude malaria. In the event of a positive finding the clinician/ward will be informed. A percentage parasitaemia is only given in cases of Plasmodium Falciparum and Plasmodium Knowlesi. 

Please note: negative films do not exclude a diagnosis of malaria blood films and should be repeated if clinically indicated. If there has been travel to the Asia-Pacific region and clinical indication, please repeat in 12-24 hours to rule out presence of Plasmodium Knowlesi.

Assay Limitations:

  • Samples more than 3 hours old may show morphological changes to the parasites and red cells due to sequestrene effect, most pertinent being the possible development of spiking on the red cells which may be confused with the fimbriation which occurs in ovale infection.
  • It is very difficult to detected very low quantities of parasites.
  • knowlesi is extremely difficult to distinguish morphologically from P.malariae.

Antigen Kit

This is an immuno-chromatographic test using monoclonal antibodies against the metabolic enzyme pLDH (parasite Lactate Dehydrogenase) of Plasmodium species.

There are two monoclonal antibodies used, one specific for Plasmodium (P) falciparum, and one pan-specific antibody that reacts with all four species found in humans:

P falciparum, P. ovale, P. vivax and P. malariae.

Assay Limitations:

  • The presence of P.knowlesi cannot be excluded or confirmed with this kit.
  • ovale, P. vivax and P. malariae cannot be distinguished from one another.
  • The test is limited to the detection of antigen to Malaria Plasmodium species. Although the test is very accurate in detecting HRP2 and pLDH, a low incidence of false results can occur. Other clinically available tests are required if questionable results are obtained. As with all diagnostic tests, a definitive clinical diagnosis should not be based on the test but be made by the physician after all clinical and laboratory findings have been evaluated.
  • Non-specific reactions can be caused by using samples that are not tested within given time frame.

 

Specifications

  • EQA Status: NEQAS
  • EQAS Scheme: Yes

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