Malaria (Plasmodium) – Serology

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Background
Malaria serology is not the recommended testing method for diagnosis of acute malaria. If malaria is suspected, submit EDTA blood and unstained slides for microscopy as per the following link: Malaria (Plasmodium) – Microscopy, RDT, PCR and Typing.

Updates
Effective May 31, 2024, malaria serology testing is no longer routinely available through Public Health Ontario’s (PHO) laboratory and requires approval prior to submission.

* Copie d'impression non contrôlée. Valide uniquement le jour de l'impression : 21 nov. 2024.

Testing Indications

The Committee to Advise on Tropical Medicine and Travel (CATMAT) provides testing indications as well as background on diagnostic testing methods in the Canadian recommendations for the prevention and treatment of malaria guidance document¹.

Serology should not be used for routine diagnosis of acute malaria. Its role is primarily limited to individuals linked to a case of transfusion-transmitted, transplant-associated, or congenital malaria with negative microscopy and PCR results, or in instances of suspected hyperreactive malarial splenomegaly (HMS) syndrome with negative microscopy and PCR results.

Acceptance/Rejection Criteria

Serologic testing for malaria is not performed routinely, and must be pre-approved by the PHO microbiologist before submission. Contact PHO’s Laboratory Customer Service Centre at 416-235-6556 or 1-877-604-4567 for pre-approval.

Specimen Collection and Handling

Specimen Requirements

Test Requested

Required Requisition(s)

Specimen Type

Minimum Volume

Collection Kit

Malaria or Plasmodium serology

General Test Requisition

Blood or serum

(must be pre-approved by PHO microbiologist prior to submission)

5.0 ml blood or 1.0 ml serum

Blood, clotted – Serum separator tube (SST)

Submission and Collection Notes

Malaria serology is not performed routinely and must be pre-approved by a PHO microbiologist before submission. Contact PHO’s laboratory customer service at 416-235-6556 or 1-877-604-4567 for pre-approval. Failure to obtain pre-approval will result in test cancellation.

Complete all fields of the requisition form, including:

Test(s) requests and indications for testing
Patient setting/population
Clinical information including symptom onset date
Travel history
Recent malariamicroscopy and PCR test results

Label the specimen container(s) with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in test cancellation or testing delay.

Limitations

Grossly haemolysed, lipemic, contaminated specimens and specimens containing anti-coagulant are unsuitable for testing.

Storage and Transport

Centrifuge tube if using SST. Specimens should be stored at 2-8°C following collection and shipped on ice packs to PHO’s laboratory as soon as possible. All clinical specimens must be shipped in accordance to the Transportation of Dangerous Good Act.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

If approved by PHO, malaria serology is forwarded to the National Reference Centre for Parasitology (NRCP) in Montreal. Turnaround time is up to 42 days from receipt at PHO’s laboratory.

Test Methods

Method: Malaria serology is performed by enzyme-linked immunosorbent assay (ELISA). It uses a mixture of recombinant antigens of all human pathogenic Plasmodium species.

Performance: The NRCP states a sensitivity of 96% and specificity of 99% in immunocompetent individuals. It detects antibodies against P. falciparum, P. vivax, P. malariae, P. ovale, and P. knowlesi. Other commercial EIAs have a reported sensitivity of 53 to 91% and specificity of 80 to 100%. ¹

Limitations: Serology may be negative early in infection or in patients with impaired immunity. False positive reactions may occur in patients with autoimmune disorders (e.g., rheumatoid arthritis). Serology may remain positive for years following clearance of infection and does not distinguish acute from chronic, past, or recurrent infection. Cross-reactivity may occur with Leishmania spp infections.

Interpretation

Malaria ELISA performed at the NRCP:

Malaria ELISA Ratio	Result	Interpretation
< 0.8	Negative	No detectable level of antibodies against Plasmodium spp.
≥ 0.8 to < 1.1	Indeterminate	Plasmodium spp. antibody status inconclusive. Repeat testing advised if clinically indicated.
≥ 1.1	Positive	Detectable level of antibodies against Plasmodium spp. Cannot distinguish between acute and remote infection. Cross-reactivity may occur with Leishmania spp.

Reporting

Results are received back at PHO’s laboratory, and reports are forwarded to the ordering physician or authorized health care provider (General O. Reg 45/22, s.18) or submitter as indicated on the requisition.

References

van den Hoogen LL, Bareng P, Alves J, Reyes R, Macalinao M, Rodrigues JM, Fernandes JM, Goméz LF, Hall T, Singh SK, Fornace K, Luchavez J, Kitchen A, Chiodini P, Espino F, Tetteh KKA, Stresman G, Sepúlveda N, Drakeley C. Comparison of Commercial ELISA Kits to Confirm the Absence of Transmission in Malaria Elimination Settings. Front Public Health. 2020 Sep 9;8:480. doi: 10.3389/fpubh.2020.00480.