diagnosis of malaria parasites include four species (P.falciparum , P.vivax P.ovale and P.malariae ) . simple and very clear presentation with pictures of different species and different stages.

1. Huda Alislam Talab
Laboratory diagnosis of
Malaria parasite

2. Peripheral Blood Smear
 Peripheral smear study still remains the simple and
gold standard confirmatory test for detection of
malarial parasites.

3. P .falciparum

4. Quantitative Buffy Coat
The quantitative buff y coat (QBC) malaria test is an
advanced microscopic technique for malaria
diagnosis.
It consists of three basic steps:
(1) concentration of blood by centrifugation
(2) staining with acridine orange stain
(3) examination under ultraviolet (UV) light source

5. Advantages
 QBC is faster (the entire tube can be screened within
minutes), more sensitive (at least as good as a thick
film) uses more blood than thick smear and
quantification is possible
Disadvantages
 It is expensive, less specific, speciation is difficult.

7. Microconcentration Technique
In this technique, blood sample is collected in
microhematocrit tube and centrifuged at high speed.
The sediment is mixed with normal serum and smear is
prepared.
 Though it increases the positivity rate
It changes the morphology of the parasite.

8. P.Falciparum

9. P .faciparum

10. Antigen Detection by Rapid Diagnostic Tests
Parasite lactate dehydrogenase (pLDH):
 It is produced by trophozoites and gametocytes of all
Plasmodium species. Currently available test kits can
differentiate pan malarial pLDH common to all species and
pLDH specific to P. falciparum
Parasite aldolase:
Produced by all Plasmodium species

11. Histidine rich protein-2 (Pf-HRP-II):
It is produced by trophozoites and young (but not
mature) gametocytes of P. falciparum.
Most of the kits are designed to detect a combination of
two antigens, one is P.falciparum specific antigen (i.e.
HRP2 or pLDH specific for P. falciparum) and other is a
pan malarial antigen (like aldolase or pan malarial
pLDH)

12. Advantages of rapid diagnostic tests
 Rapid diagnostic tests are simple to perform, don’t
need extra equipment or trained microscopist
 Sensitivity: Rapid diagnostic tests are more than 90%
sensitive .

13.  pLDH is produced by the viable parasites, hence it is
used to monitor the response for treatment . However,
HRP2 remains positive even after treatment
 HRP2 is a reliable marker to diagnose malaria in
pregnancy
 Intensity of the band is directly proportional to the
parasitemia and severity of the disease.

14. Disadvantages of rapid diagnostic tests
Rapid diagnostic test kits are expensive
Cannot differentiate between the non falciparum malaria
species
Gametocytes cannot be detected
False positive bands appear in rheumatoid arthritis factor
positive cases.

15. Antibody Detection
ELISA
IFA
IHA
are available using soluble malarial antigens.
 Detection of antibody in serum indicates past malaria
infection and is useful for:
 Epidemiological survey in malaria
 Screening of blood bank to identify the infected donors.

16. Culture
Culture techniques for malaria are mainly used for
preparation of malaria antigens. However, they are not
used for diagnosis.
RPMI 1640 medium(Roswell Park Memorial Institute) in
a continuous flow system mixed with a thin layer of RBC
and an overlay medium consists of human serum
maintained with 7% CO2 and 1–5% O2

17.  Modified Eagle medium (MEM)
 RPMI 1630
 Medium 199.

18. Molecular Diagnosis
DNA probe: Highly sensitive, detects even if the
parasite count is low less than 10/μL
PCR
 It can detect a single P. falciparum in 20 μL of blood
 It is 100 times more sensitive than thick blood smear
Speciation can be done
 Drug resistance genes can be detected
 Useful tool for epidemiological study.

19. Other tests
Measurement of haemoglobin or packed cell volume
when there is malaria with heavy parasitaemia
Measurement of blood glucose to detect hypoglycaemia
Total white cell count and platelet count
Coagulation tests if abnormal bleeding is suspected in
falciparum malaria

20. Testing urine for free haemoglobin when malaria
haemoglobinuria is suspected
Blood urea and serum creatinine
Testing urine for protein when nephrotic syndrome is
suspected
Screening for G6PD deficiency before treating a patient
with primaquine

21. Trophozoite

23. Trophozoite of P.falciparum (ring form)

26. Hyperparasitaemia of
P.falciparum

27. Hyperparasitaemia of P.falciparum

28. Schizont of P.falciparum

31. Gametocyte of P.falciparum

34. Laboratory indices of poor prognosis in falciparum
malaria
Heavy parasitaemia with more than 5% of red cells
parasitized
Presence of mature trophozoites, malaria pigment in
neutrophils, and schizonts in peripheral blood films
Peripheral leucocytosis of more than 12 000/l.
 Low cerebrospinal fluid lactate level
 Low antithrombin 111 levels

35. Serum creatinine high
 Blood urea nitrogen high
Packed cell volume low or haemoglobin lower than 7.0 g/dl
(in previously non-anaemic person).
Blood glucose low

36. P vivax

40. P .malariae

41. Trophozoite of P.malariae (band form)

43. P.ovale

46. In thick blood film
No. of parasites x 8000
No. of WBC
WBC count x Parasites counted against
100WBC
100
The plus system
+ = 1–10 parasite per 100 thick film fields
++ = 11–100 parasite per 100 thick film fields
+++ = 1–10 parasite per thick film field

47. Thin blood film:
1. Select an area of the thin film where the total number of red cells is
approximately 250 per field.
2. Count the number of parasitized red cells in 8 fields, i.e. approximately
2 000 cells.
3. Divide by 20 to calculate the percentage (%) of parasitized cells.
Counting % of infected RBCs in thin films
1. Count 500 RBCs
2. Count the number of infected ones divide by 5 = % of infected
RBC.