Over-reliance on thin and thick blood film for diagnosis and radical treatment in malaria in India
There is an over-reliance on thick and thin smear in diagnosis of
Malaria. And radical treatment is given only on smear positivity. Blood
smear assess for the presence of schizonts, gametocytes, and malarial
pigment in neutrophils and monocytes. Before reporting a negative result,
at least 200 oil immersion visual fields at a magnification of 1000?
should be examined on both thick and thin smears, which has a sensitivity
of 90%. A negative test DOES NOT rule out malaria. Repeated tests may
have to be done in all doubtful cases1,2. Duration of the illness, level
of parasitemia, expertise of the technician (which is questionable in
India because of lack of retraining and supervision or cross-checking) and
the method of examination may all have a bearing on the diagnostic
accuracy of the blood smear test1,2. In absence of radical treatment the
reservoir of Plasmodium vivax cases will expand (though not P. falciparum
as there is no hepatic stage) The level of parasitemia may be expressed
either as a percentage of parasitized erythrocytes or as the number of
parasites per microliter of blood.
In falciparum malaria, parasitized erythrocytes may be sequestered in
tissue capillaries resulting in a falsely low parasite count in the
peripheral blood ('visible' parasitemia)1.
Parasitemia can be decreased by inadequate anti-malaria treatment which is
possible in prsence of large number of quacks. this lead to false negative
result.
Just giving Chloroquine/ SP+AS combination in malaria is not going to
eradicate gamatocytes so chances of relapse always present, i.e.
reservior of infection in the community increases. Another reasons are
false negative reporting and lack of follow up lead to failure of
primaraquine treatment in potential malaria case. Such cases would be
having infection and continue to be reservior of infection and suffering
from relapses. 14 days of treatment of primaquine is essential with
chloroquine/SP+AS. But use of this drug is also questionable in view of
hemolysis in G6PD deficiency states.
Moreover, in absence of active case finding forenightly (large number of
vacant posts of Male Health workers) and indiscriminately using
chloroquine can lead to increase in reservior.
Rapid Response:
Over-reliance on thin and thick blood film for diagnosis and radical treatment in malaria in India
There is an over-reliance on thick and thin smear in diagnosis of
Malaria. And radical treatment is given only on smear positivity. Blood
smear assess for the presence of schizonts, gametocytes, and malarial
pigment in neutrophils and monocytes. Before reporting a negative result,
at least 200 oil immersion visual fields at a magnification of 1000?
should be examined on both thick and thin smears, which has a sensitivity
of 90%. A negative test DOES NOT rule out malaria. Repeated tests may
have to be done in all doubtful cases1,2. Duration of the illness, level
of parasitemia, expertise of the technician (which is questionable in
India because of lack of retraining and supervision or cross-checking) and
the method of examination may all have a bearing on the diagnostic
accuracy of the blood smear test1,2. In absence of radical treatment the
reservoir of Plasmodium vivax cases will expand (though not P. falciparum
as there is no hepatic stage) The level of parasitemia may be expressed
either as a percentage of parasitized erythrocytes or as the number of
parasites per microliter of blood.
In falciparum malaria, parasitized erythrocytes may be sequestered in
tissue capillaries resulting in a falsely low parasite count in the
peripheral blood ('visible' parasitemia)1.
Parasitemia can be decreased by inadequate anti-malaria treatment which is
possible in prsence of large number of quacks. this lead to false negative
result.
Just giving Chloroquine/ SP+AS combination in malaria is not going to
eradicate gamatocytes so chances of relapse always present, i.e.
reservior of infection in the community increases. Another reasons are
false negative reporting and lack of follow up lead to failure of
primaraquine treatment in potential malaria case. Such cases would be
having infection and continue to be reservior of infection and suffering
from relapses. 14 days of treatment of primaquine is essential with
chloroquine/SP+AS. But use of this drug is also questionable in view of
hemolysis in G6PD deficiency states.
Moreover, in absence of active case finding forenightly (large number of
vacant posts of Male Health workers) and indiscriminately using
chloroquine can lead to increase in reservior.
References:
1.http://www.malariasite.com/malaria/DiagnosisOfMalaria.htm
2.White NJ. Malaria. Manson's Tropical Diseases (Edited by: Cook GC, Zumla
AI, Weir J). Philadelphia, PA: WB Saunders 2003;1205-1295
Competing interests: No competing interests