Malaria laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: João André Alves Silva, M.D. [2]

Overview

The diagnosis of malaria is confirmed by the identification of the malaria parasite in the patient's blood under microscopy. Laboratory tests may also reveal anemia with decreased hemoglobin, hematocrit, and haptoglobin in addition to either a decreased or increased leukocyte count. Biochemistry may reveal hypoglycemia, elevated LDH, acidosis, and mild hyponatremia due to vomiting and diarrhea. In severe disease, elevated creatinine, proteinuria, and hemoglobinuria may be present secondary to renal failure. Other malaria-specific tests include: the antigen detection test, PCR, and serology test for the presence of antibodies against the plasmodium. Drug resistance tests should also be performed to assess the susceptibility of the microorganism to the antimalarial drugs.

Laboratory Findings

Microscopic Diagnosis

• This technique remains the gold standard for laboratory confirmation of malaria. Malaria parasites can be identified by examining under the microscope a drop of the patient's blood, spread out as a "blood smear" on a microscope slide. This is possible because each of the four major parasite species has distinguishing characteristics.

• Prior to examination, the specimen is stained (most often with the Giemsa stain) to give the parasites a distinctive appearance.

• Two types of blood films are traditionally used:

• Thin films - similar to usual blood films and allow species identification since the parasite's appearance is best preserved in this preparation.
• Thick films - allow the microscopist to screen a larger volume of blood, and are about eleven times more sensitive than the thin film, so picking up low levels of infection is easier on the thick film, but the appearance of the parasite is much more distorted and therefore distinguishing between the different species can be much more difficult.

This test has the limitation of depending on the quality of the reagents, of the microscope, and on the experience of the laboratories.

Antigen Detection

• Considered a "Rapid Diagnostic Tests" (RDTs), this test offers a useful alternative to microscopy in situations where reliable microscopic diagnosis is not available.

• Detects the antigens derived from malaria parasites. It most often uses a dipstick or cassette format, and provides results in 2-15 minutes.

• Although they may be used in some settings, before malaria RDTs can be widely adopted, several issues remain to be addressed, including:

• Improving their accuracy
• Lowering their cost
• Ensuring their adequate performance under adverse field conditions

• In 2007, the U.S. Food and Drug Administration (FDA) approved the first RDT for use in the United States. This RDT is approved for use by hospital and commercial laboratories, not by individual clinicians or by patients themselves. It is recommended that all RDTs are followed-up with microscopy to confirm the results and if positive, to quantify the proportion of red blood cells that are infected. The use of this RDT may decrease the amount of time that it takes to determine that a patient is infected with malaria.

Molecular Diagnosis

PCR

• Parasite nucleic acids are detected using polymerase chain reaction (PCR).
• Although this technique may be slightly more sensitive than smear microscopy, it is of limited utility for the diagnosis of acutely ill patients in the standard healthcare setting.
• PCR results are often not available quickly enough to be of value in establishing the diagnosis of malaria infection.
• PCR is most useful for confirming the species of malarial parasite after the diagnosis has been established by either smear microscopy or RDT.
• Levels of parasitemia are not necessarily correlative with the progression of disease, particularly when the parasite is able to adhere to blood vessel walls.

Serology

• Serology detects antibodies against malaria parasites, using either indirect immunofluorescence (IFA) or enzyme-linked immunosorbent assay (ELISA).
• Serology does not detect current infection but rather measures past exposure.

Drug Resistance Tests

• Drug resistance tests must be performed in specialized laboratories to assess the susceptibility to antimalarial compounds of parasites collected from a specific patient.
• Two main laboratory methods are available:

• In vitro tests - The parasites are grown in culture in the presence of increasing concentrations of drugs; the drug concentration that inhibits parasite growth is used as endpoint.
• Molecular characterization - Molecular markers assessed by PCR or gene sequencing also allow the prediction, to some degree, of resistance to some drugs. CDC recommends that all cases of malaria diagnosed in the United States should be evaluated for evidence of drug resistance.

Shown below is a table summarizing nonspecific laboratory abnormalities associated with malaria.

Laboratory findings

Test	Findings
Complete blood count	Decreased hemoglobin Decreased hematocrit Microcytosis Decreased haptoglobin
White blood cell count	Elevated or Decreased Leukocyte Count
Biochemistry	Hypoglycemia Elevated creatinine Elevated LDH Possible hyponatremia Acidosis: High lactate; Low bicarbonate
Coagulation	Thrombocytopenia
Urinalysis	Proteinuria Hemoglobinuria

Gallery

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  Magnified 1000x, this Giemsa-stained photomicrograph revealed some of the ultrastructural morphology exhibited by an immature Plasmodium vivax schizont Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Ultrastructural morphology exhibited by a Plasmodium falciparum gametocyte, i.e., sexual erythrocytic stage, of this malarial parasite, which was found in a blood sample from a patient who had been treated with an unknown therapeutic agent Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Ultrastructural morphology exhibited by a ring-form,Plasmodium falciparum malarial parasite, which was found in a blood sample from a patient who had been treated with an unknown therapeutic agent. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnification of 1125X, this photomicrograph of a simian blood sample revealed the presence of a mature simian malarial schizont and gametocyteAdapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film blood smear micrograph depicts numerous ring-form Plasmodium falciparum trophozoites, as well as a number of white blood cells (WBC).Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film blood smear micrograph depicts three pinkish-colored, crescent-shaped Plasmodium falciparum gametocytes.Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film blood smear micrograph depicts two pinkish-colored, crescent-shaped Plasmodium falciparum gametocytes. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts an immature Plasmodium malariae schizont, which contains three chromatin masses, a light cytoplasm, and a dark pigment Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts two Plasmodium malariae schizonts Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts a mature Plasmodium malariae schizont, which contains nine merozoites Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film blood smear micrograph depicts a young, growing Plasmodium malariae trophozoite, which had just past its ring-stage in its maturation process.Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film blood smear micrograph depicts an old Plasmodium malariae trophozoites (Rt), and an immature schizont containing eight chromatin masses (Lt). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts a mature, band-form Plasmodium malariae trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts an older, growing Plasmodium malariae trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts a growing Plasmodium malariae basket-form trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film blood smear micrograph depicts a mature Plasmodium malariae schizont, which contained what appeared to be 8 merozoites arranged in a rosette pattern within its cytoplasm Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film blood smear micrograph depicts a mature Plasmodium malariae schizont, containing ten merozoites within its scattered, faint cytoplasm. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts a growing Plasmodium malariae trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film blood smear micrograph depicts an immature Plasmodium malariae schizont, displaying four cytoplasmic chromatin masses Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film blood smear micrograph depicts an old amoeboid Plasmodium vivaxtrophozoite, displaying a distinctly pigmented cytoplasm. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film blood smear micrograph depicts two ring-form Plasmodium vivaxtrophozoites, each displaying a stippled cytoplasm Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film blood smear micrograph depicts an mature Plasmodium vivax schizont with 14 chromatin masses Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film photomicrograph of a blood smear, revealed the presence of a ring-formPlasmodium vivax trophozoite on the right, which contained three chromatin dots Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film photomicrograph of a blood smear, revealed the presence of a triple ring-form Plasmodium vivax trophozoite on the right, and a young, growing amoeboid trophozoite on the lef, both displaying intracytoplasmic Schüffner's dots Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film photomicrograph of a blood smear, revealed the presence of a ring-formPlasmodium vivax trophozoite (upper left), and a growing amoeboid trophozoite displaying intracytoplasmic Schüffner's dots (right). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film photomicrograph of a blood smear, revealed the presence of a young growing Plasmodium vivax amoeboid trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film photomicrograph of a blood smear, revealed the presence of twoPlasmodium vivax schizonts, an immature form on the left, and a mature form on the right. Merozoites are undergoing development in these two infected erythrocytes, and they are almost ready to be liberated from the mature schizont. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thin film photomicrograph of a blood smear, revealed the presence of a number ofPlasmodium vivax “free” merozoites, which had been liberated from the confines of their occupied erythrocyte Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of a darkly-granulated eosinophil, a type of white blood cell, also known as a granulocyte due to these intracytoplasmic granules Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of a Plasmodium vivaxtrophozoite, as well as a number of artifactual mold hyphae and a spore Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of a growing Plasmodium vivaxtrophozoites, as well as a number of artifactual mold hyphae Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of an immature Plasmodium vivax schizont containing a number of chromatin masses Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of an immature Plasmodium vivax schizont containing a number of chromatin masses Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of a growing Plasmodium vivaxamoeboid trophozoite. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of a growing Plasmodium vivaxtrophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed the presence of a number of immaturePlasmodium vivax schizonts Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick film photomicrograph revealed a Plasmodium vivax gametocyte, reddish in color, and displaying virtually no visible cytoplasm Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this thick-film, Giemsa-stained photomicrograph revealed the presence of an immaturePlasmodium malariae schizont (cntr), which is situated to the left of an eosinophile. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Magnified 1125X, this photomicrograph revealed the presence of a Plasmodium malariae immature schizont. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film Giemsa stained micrograph depicts a mature Plasmodium ovale trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film Giemsa stained micrograph depicts a growing Plasmodium ovale trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thin film Giemsa stained micrograph depicts a Plasmodium falciparum gametocyte Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film Giemsa stained micrograph depicts a mature Plasmodium malariae schizont Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film Giemsa stained micrograph reveals a mature Plasmodium vivax trophozoite, and gametocyte Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film Giemsa stained micrograph showing two mature Plasmodium vivax schizonts each containing merozoites Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film Giemsa stained micrograph revealing a P. falciparum gametocyte (Arrow Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  Thick film Giemsa stained micrograph revealing a P. falciparum gametocyte (Cntr). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  The remnant cell membranes of the RBCs in this thick film micrograph are known as “ghosts”, and surround a single WBC Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph depicts a platelet artifact that could be mistaken for a malaria parasite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph reveals a number of ring-form staged Plasmodium falciparumtrophozoites Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This Giemsa stained slide reveals a P. falciparum, P. ovale, P. malariae, P. vivax, gametocyte Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  These thin film Giemsa stained micrographs reveal a Plasmodium falciparum micro- and macrogametocyte Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  These thin film Giemsa stained micrographs show ring-form Plasmodium vivax and P. falciparumtrophozoites Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph reveals a ring-form Plasmodium falciparum trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph reveals a mature P. vivax, P. malariae, and P. ovale schizont Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph reveals growing P. vivax, P. malariae, and P. ovale trophozoites Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph depicts a Plasmodium ovale micro- (Lt) and macrogametocyte (Rt). Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph reveals a mature Plasmodium ovale trophozoite. Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  These thin film Giemsa stained micrographs reveal growing Plasmodium ovale trophozoites Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph depicts a ring-form Plasmodium ovale trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph depicts a Plasmodium malariae micro- (Lt) and macrogametocyte Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph revealed a mature Plasmodium malariae trophozoite Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  These thin film Giemsa stained micrographs depict a Plasmodium vivax macro- (Lt), and microgametocyte Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph depicts an immature Plasmodium vivax schizont Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.

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  This thin film Giemsa stained micrograph revealed a single RBC containing two ring-form Plasmodium vivax trophozoites Adapted from Public Health Image Library (PHIL), Centers for Disease Control and Prevention.