Lab diagnosis of malaria

Lab diagnosis of malaria_Rashid
• Microscopy
– To detect and identify malarial parasites in peripheral blood films.
• Concentrating parasites in venous blood by centrifugation when they cannot be found in blood films
• Using a rapid malaria Ag or enzyme detection test
• Other nonspecific tests – Hb, PCV, Blood glucose, total WBC & platelet count.
Examination of the blood:-
• Collection of blood
- Best prepared directly from capillary blood
- In EDTA bulb (used within 30 minutes)
• Time of collection
- As soon as possible if malaria is suspected
- Before administering antimalarials
- During pyrexial phase
Types of blood films:-
1. Thick films :
- 30 to 40 times more sensitive than thin films
- More suitable for detection of malaria parasite when they are few in number
- Blood is not fixed; RBCs are lysed during staining (only parasitic forms will be seen)
2. . Thin films :
- To confirm the Plasmodium species
- assists in the identification of mixed infections
- Blood is fixed; parasites are seen within the RBCs
-Also helps in assessing the response to treatment especially in areas where drug resistance is suspected (by counting the number of parasitized RBCs before and after the treatment.



Fixation and staining:-
• Fixation – thin films are fixed with absolute alcohol for 1 to 2 minutes.
• Staining – films are stained with Romanowsky stain: giemsa, field’s, Wright’s or Leishman’s
• Giemsa – 10% solution for 10 minutes.

Reporting of blood film
• Look for the different morphological forms of parasite in blood smear:
1. Trophozoites / ring forms
2. Schizont
3. Gametocytes
• Identify species – differences in the characteristics of morphological forms in different species
Alternate methods for laboratory diagnosis include:
• Antigen Detection

1) To detect antigens derived from malaria parasites
2) "Rapid Diagnostic Tests" (RDTs)
3) offer a useful alternative to microscopy in situations where reliable microscopic diagnosis is not available.
• Molecular Diagnosis

1. Parasite nucleic acids are detected using polymerase chain reaction (PCR).
2. This technique is more accurate than microscopy.
3. It is expensive, and requires a specialized laboratory.


• Serology - Not used commonly

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