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Revista da Sociedade Br asileir a de Medicina Tr opical 3 8 ( 2 ) :1 9 4 -1 9 5 , mar-abr, 2 0 0 5
Evaluation of an immunochromatography test for malaria
diagnosis under different storage conditions
Avaliação de um teste de imunocromatografia para o diagnóstico
de malária em diferentes condições de estocagens
Roberta de Souza Rodrigues Penhalbel
1, Érica Fugikaha
1, Alexandre Lorenzetti
1, Renata Tomé Alves
1,
Carlos Eugênio Cavasini
1, Andréa Regina Baptista Rossit
1, Vanja Suely Pachiano Calvosa
2,
Álvaro Augusto D‘Almeida Couto
3and Ricardo Luiz Dantas Machado
1ABSTRACT
Th i s stu d y a i m e d to e va lu a te th e se c o n d - ge n e ra ti o n Op ti Ma l te st f o r m a la ri a d i a gn o si s u n d e r va ri o u s sto ra ge c o n d i ti o n s. It d e te c te d a ll th e p o si ti ve sa m p le s, e x c e p t f o r two Plasmo dium malar iae sa m p le s. Fu rth e r re se a rc h e va lu a ti n g d i ve rse e n vi ro n m e n ta l c o n d i ti o n s a re i m p o rta n t f o r ICT te st a p p li c a b i li ty i n Bra zi li a n m a la ri a a re a s.
Ke y-words: Ma la ri a . Plasmo dium sp. Di a gn o si s. Im m u n o c h ro m a to gra p h y.
RESUMO
Este e stu do o b je tiva a va lia r o de se m pe n ho do te ste OptiMa l de se gu n da ge ra ç ã o pa ra o dia gn ó stic o de m a lá ria e m dife re n te s c o n diç õ e s de e sto c a ge m . Ele de te c to u to da s a s a m o stra s po sitiva s, e xc e to du a s a m o stra s de Plasmodium malariae. Fu tu ra s p e sq u i sa s a va li a n d o a s d i ve rsa s c o n d i ç õ e s a m b i e n ta i s sã o i m p o rta n te s p a ra a a p li c a b i li d a d e d o ICT e m á re a s d e m a lá ri a b ra si le i ra .
Pal avr as-chave s: Ma lá ri a . Plasmo dium sp. Di a gn ó sti c o . Im u n o c ro m a to gra f i a .
1 . Departamento de Doenç as Dermatológic as Infec c iosas e Parasitárias da Fac uldade de Medic ina de São José do Rio Preto, São José do Rio Preto, SP. 2 . Seç ão de Parasitologia do Instituto Evandro Chagas da Sec retaria de Vigilânc ia em Saúde do Ministério da Saúde, B elém, PA. 3 . Gerênc ia de Projeto e Pesquisa em Ensino-GPEPS-SES Mac apá, AP.
Financ ial suppo r t was pr o vide d b y FAPESP ( 0 2 /0 9 5 4 6 -1 ) and CNPq ( 3 0 2 3 5 3 /0 3 -8 ) . The pr o to c o l fo r this study was r e vie we d and appr o ve d b y the Re se ar c h B o ar d o f the Fac ulty o f Me dic ine o f São J o sé do Rio Pr e to ( 1 2 4 6 /2 0 0 3 ) .
Add r e s s to: Dr. R i c a r do Lu i z Da n ta s Ma c h a do. Ce n tr o de I n ve s ti ga ç ã o de Mi c r o r ga n i s m o s /FMS J R P. Av. B r i ga de i r o Fa r i a Li m a 5 4 1 6 , 1 5 0 9 0 - 0 0 0 , S ã o J o s é do R i o Pr e to , SP.
Te l: 5 5 1 7 2 1 0 5 7 0 0 r amal 5 8 8 7 e -mail: r ic ar do mac hado @ fame r p. b r Re c e b ido par a pub lic aç ão e m 8 /9 /2 0 0 4 Ac e ito e m 1 3 /1 2 /2 0 0 4
COMUNICAÇÃO/COMMUNICATION
Malar ia is e nde mic in the B r azilian Amazo n r e gio n. Of th e fo ur k n o wn h um a n m a la r ia pa r a s ite s , Pla sm o d i u m f a lc i pa ru m, Pla sm o di u m vi va x, Pla sm o di u m m a la ri a e and
Pla sm o d i u m o va le, o nly the fir st thr e e spe c ie s have b e e n de te c te d in B r azil. The imme nse ar e a o f land and wate r, and the unc o ntr o lle d o c c upatio n o f the B r azilian Amazo n r e gio n, asso c iate d with the lac k o f pe r so nne l to c ar r y o ut r apid diagno sis, all c o ntr ib ute to the e le vate d numb e r o f malar ia c ases in this r egio n2. Rapid and ac c ur ate diagno sis o f malar ia
is e sse ntial fo r r e duc ing mo r b idity and mo r tality as we ll as fo r c o ntr o l pur po se s. Lab o r ato r y diagno sis o f malar ia has tr aditio nally r e lie d upo n ide ntific atio n o f the pr o to zo an in per ipher al b lo o d using mic r o sc o pic examinatio n o f thic k and thin b lo o d sme ar s1 0. This pr o c e dur e is lab o r-inte nsive , time
c o nsuming and dependent o n tr aining and exper t kno wledge,
par tic ular ly fo r the inte r pr e tatio n o f mixe d infe c tio ns and in c ase s with lo w par asite mias1 4.
During the last few years, alternative immunochromatography tests ( ICT) have been developed showing potential for enhanc ing speed and ac c urac y in the diagnosis of both fa lcipa rum and
vi va x malar ia, par tic ular ly whe r e diagno stic te sts ar e no t available, suc h as in rural and remote areas8. Newer ICTs make
use of a sec ond pan-malarial antibody, whic h is supposed to detec t all four malarial spec ies that infec t humans. The OptiMal te st ( Flo w, USA) , whic h is c ur r e ntly mar k e te d b y DiaMe d, Switzerland, detec ts a Pla sm o dium fa lcipa rum-spec ific lac tate dehydrogenase ( LDH) and a sec ond-generation pLDH c ommon to all human malaria parasites3. The purpose of the present study
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Pe nha lbe l RSR e t al
A to ta l o f 1 1 1 po s itive ( 7 5 Pla s m o d i u m vi va x , 3 4
Pla sm o dium fa lcipa rum and 2 Pla sm o dium m a la ria e) and 4 0 negative samples analyzed by the thic k blood smear method we r e also e valuate d using the OptiMal te st ( ac c o r ding to manufac turer’s instruc tions) . The samples from P. viva x malaria patients showed parasite density between 2 5 0 and 5 ,5 0 0 infec ted r e d b lo o d c e lls/mm3, while in P. f a lc i p a ru m sample s the
parasitemia ranged from 4 6 5 to 7 ,5 0 0 infec ted red blood c ells/ mm3. Two samples of P. m a la ria e showed parasite density below
5 0 infec ted red blood c ells/mm3. The OptiMal-IT kits (
DiaMed-ID AS) were stored at three different temperatures ( 2 5 ° C, 3 0 ° C and 3 9 ° C) for 2 4 , 4 8 and 7 2 hours before use.
The OptiMal-IT kit provided negative results in all 4 0 samples with no parasites in the microscopy examination ( control group) . The test could detect the positive samples that were seen in the microscopy examination at all evaluated temperatures and periods of storage. It was observed that the pink-line signals indicating positive results were constant under the same conditions. We could not detect either of the two P. m a la ria e samples at any of the different temperatures and storage periods for the kits.
Notable antigens for the diagnosis of malaria are histidine-rich protein II and lactate dehydrogenase, which are expressed in merozoite-staged malaria, secreted to erythrocyte cytoplasm or passively diffuse to human plasma5 9. It is a crucial issue to consider
the possible decline in test quality due to reduced shelf life under tropical conditions. Good stability and durability of the test strips were previously indicated for the ParaSight-F dipstick test after one year of storage at room temperature6. Recently, Figueiredo
Filho et al2 evaluated the ICT Malaria Pf/PvTM ( histidine-rich protein
a n tige n I I - AMRAD, Aus tr a lia ) s to r a ge a t th r e e diffe r e n t temperatures ( 2 5 ° C, 3 0 ° C and 3 7 ° C) for 2 4 hours before use, and observed that the color of positive results ( pink line) loses its intensity as the temperature increased, which constitutes a limitation for its use. On the other hand, the OptiMal-IT manufac turer’s recommendation is to use the test kit within a maximum of three months when stored under ambient c onditions. Nevertheless, storage conditions are an important factor for the efficiency of the ICT, espec ially in the north of B razil ( Amazon region) were temperatures often surpass 3 0 ° C.
Our results show excellent performance of the OptiMal-IT test under the different conditions evaluated. However we could not detect samples of P. m a la ria e, probably because of its well-recognized ab ility to de te c t mainly the mo st patho ge nic human malar ia
P. fa lcipa rum and P. viva x infections3. Another reliable explanation
is the fact that these samples showed low parasitemia which is a limitation advised by the manufacturer, stating that the test may not be a hundred percent correct in samples with parasitaemias under < 1 0 0 red blood cells/mm3. Additionally, previous studies3 7 have
demonstrated that OpitMal-IT test is unreliable for detection of
Pla sm o dium o va le and Pla sm o dium m a la ria e.
The ICTs are known for their easy use, even by inexperienc ed personnel1 0. Future studies with the same format as that used in
the present work are nec essary. Our data suggest that OptiMal-IT test c an be used to perform malaria diagnosis in the Brazilian Amazon region, despite the high temperatures. Further researc h into diverse environmental c onditions, suc h as humidity, are of great importanc e for establishment of ICT test applic ability in Brazilian endemic and nonendemic malaria areas.
ACKNOWLEDGEMENTS
To all patie nts e nr o lle d in this study.
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