MALARIA DIAGNOSIS A CLOSER LOOK AT THE LINK BETWEEN RAPID DIAGNOSTIC TESTS AND MICROSCOPY

1. MALARIA DIAGNOSIS
A CLOSER LOOK AT THE LINK
BETWEEN RAPID DIAGNOSTIC TESTS
AND MICROSCOPY
PRESENTED BY
L. BENARD
Medical laboratory scientist
HPSIF, DOUALA

2. INTRODUCTION
An essential component of malaria control and
elimination strategies is prompt, accurate diagnosis
and treatment (within 24 hours of onset of illness) of
patients with an effective medicine.
Parasitological testing is the only way to diagnose
malaria accurately in febrile patients. Treatment based
on diagnostic testing is good clinical practice and has
many advantages over presumptive treatment of all
fever episodes:


3. INTRODUCTION
Since early 2010, WHO has recommended prompt
parasitological confirmation by microscopy or
an RDT for all patients suspected of having malaria,
before treatment is started.
 Treatment solely on the basis of clinical suspicion
should be considered only where parasitological
diagnosis is not accessible.

4. INTRODUCTION
High-quality microscopy services for the diagnosis of
malaria are not widely available.
Microscopy requires trained staff, well-maintained
equipment, a regular supply of reliable reagents, clean
water and electricity, and a well-executed quality
management system.
For these reasons, RDTs were introduced in 1990s
detect malaria parasite antigens/antibodies in a
fingerpick blood sample

5. INTRODUCTION
The prevalence of malaria in a wide range of settings, its
aspecifc clinical presentation, which overlaps with that of
many other diseases, and the acute and life-threatening
nature of the disease require universal access to
parasitological diagnosis,
Microscopy and RDTs both show adequate performance in
the diagnosis of malaria in febrile patients .
Each test has characteristics that make it useful in particular
clinical situations or settings. Therefore, in most countries,
both are needed

6. RAPID DIAGNOSTIC TESTS (RDTS)
•RDTs, sometimes called ‘rapid diagnostic devices’,
facilitate the diagnosis of malaria by providing
evidence of the presence of Plasmodium-specifc proteins
(antigens) in human blood
• Although many products are available on the market, some
can detect only one species (e.g. only P. falciparum), while
others also detect further species of the parasite

7. RDTS........
• Malaria RDTs currently on the market detect the
following parasite antigens in various combinations:
• Histidine-rich protein 2 (HRP2),
• Plasmodium lactate dehydrogenase (pLDH), and
• Aldolase.

8. RDTS........
• HRP2 is produced only by P. falciparum.
• Aldolase is produced by all four species and can therefore
be used to identify all human malaria parasites.
• pLDH is also common to all four species and can be
detected by antibody-binding antigen epitopes that are
common to all species
• We have present HRP II (proline) and pLDH (Carestart)

9. RDTS........
WHO recommends that such tests should have a
sensitivity of >95% in detecting plasmodia at densities
of more than 100 parasites per µl of blood.
Current tests are based on the detection of histidine-
rich protein 2 (HRP2), which are specific for P.
falciparum, how ever some cases of gene mutation has
been recorded.

10. MICROSCOPY
Microscopy has many advantages, including:
low direct costs if there is already a high volume of samples
and the infrastructure to maintain the service;
highly sensitive for clinical malaria, if the quality of
microscopy is good (including competent microscopists, good
equipment and reagents and an appropriate workload), although
not sensitive for detecting low-density parasitaemia;
allows differentiation of malaria species and parasite stages;
allows determination of parasite density;
allows assessment of drug effects; and
can be used to diagnose other diseases

11. MICROSCOPY
It can be difficult to maintain good quality of microscopy, for
various reasons:
The need for competent Microcopists
The need for adequate training and supervision of laboratory
staff;
The need to rely on electricity;
Delays in providing results to patients; and
The need to maintain quality assurance and control of
laboratory services.

12. Choice of malaria test
Several factors should be considered in choosing
whether RDTs or microscopy should be used for
diagnosis in certain settings and clinical situations,
including the existence of a laboratory, workload,
malaria prevalence, the skill of personnel performing
the test

14. recommendation
• The two methods be used based on the situation as
explained in the presentation

16. REFERNCES
• Universal access to malaria diagnostic testing: an operational manual.
1.Malaria – diagnosis. 2.Antimalarials – therapeutic use. 3.Malaria –
drug therapy.Diagnostic tests, Routine – utilization. 5.Manuals.
I.World Health Organization.ISBN 978 92 4 150209
• Guidelines for the treatment of malaria -- 2nd edition.1.Malaria –
drug therapy. 2.Malaria – diagnosis. 3.Antimalarials – administration
and dosage. 4. Drug therapy, Combination. 5.Guidelines. I.World
Health Organization.
• Guidelines for treatment of Malaria 3rd edition 2015