Laboratory diagnosis of malarial parasite:

Blood is collected from finger tips or ear lobe in older children and adults. In case of infants blood is collected from great toe.
Smear should be examined atleast twice daily until parasite is detected.

i. Light microscopy:

After blood collected from capillary, smear is prepared and stained with Romanwsky’s stain.
Thick smear is used for detecting the parasite, quantitating parasitaemia, demonstrating malarial pigments.
Thin smear is used for detecting parasites and also for determining the species.
Diagnostic of falciparum is
- –detection of multiple rings in a single RBC with accole form
- Presence of maurer’s dots in RBC containing large ring
- Presence of characteristics banana shaped gametocyte

ii. Fluorescence microscopy:

Kawanoto technique is a fluorescent staining method for demonstrating malarial parasites.
In this method, blood smears are prepared on a slide and are stained with acridine orange. This is a differential staining. Nuclear DNA stained green and cytoplasmic RNA stained red.
The stained slide is examined with fluorescence microscope for identification of parasite.

iii. Quantitative buffy coat (QBC):

This is a sensitive method for detection of malarial parasite.
It is based on the ability of acridine orange to stain nucleic acid of parasite.
In this method, blood is collected in a capillary tube coated with fluorescent dye and is subjected to microhaematocrit centrifugation in a specialized centifuse.
After centrifugation the buffy coat in the tube is examined directly under a fluorescence microscope. Parasite appear brilliant green.
QBC is more sensitive than thick smear preparation.

iv. Serology:

v. Dipstick test:

It is a rapid diagnostic test extremely useful for rapid diagnosis of cerebral malaria.
This is an enzyme immunoassay which detects histidine rich protein 2 (pf HRP-2) antigen, a metabolic product specifically produced by falciparum.
Monoclonal antibodies produced against pfHRO-2 antigen is employed in the test to detect antigen in serum or urine.
Dipstick test is only useful for detecting falciparum

vi. Molecular diagnosis:

DNA probe is high;y sensitive. It can detect even a low parasitaemia (<10 parasite/ µl of blood). It is useful to detect drug resistant parasites.
PCR is highly sensitive and can detect a single P. falciparum in 20µl of blood using PBRK1 primer.
PCR can be used for identification of malarial parasite

vii. Biochemical diagnosis:

A normochromic, normocytic haemolytic anaemia
Leucopenia
High Erythrocyte sedimentation rate
Prolonged prothrombin and partial thromboplastin time in severe infection
Normal plasma concentration of electrolytes, blood and urea nitrogen in uncomplicated malaria
Decreased anti-thrombin II levels is mild infection
Metabolic acidosis
Hypergamma-globulinaemia
Normal urine analysis
Biological false positive reaction with VDRL test