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ORIGINAL ARTICLE
Sensitivity of Parasitological Tests in Imported Plasmodium vivax Malaria in Adults and Impact of Chemoprophylaxis and Attack Type ´ ´ e, ´ MD,∗ Christophe Rapp, MD,† Herve´ Delacour, PharmD,∗ Sebastien Larrech ´ Nancy Sanmartin, MD,∗ Cecile Ficko, MD,† Christine Bigaillon, MD,∗ Dina Andriamanantena, † ∗ ´ MD, Jean-Etienne Pilo, MD, and Audrey Merens, MD∗ ∗ Service
ˆ de Biologie M´edicale; † Service des Maladies Infectieuses et Tropicales, Hopital d’Instruction des Arm´ees B´egin, Saint-Mand´e, France DOI: 10.1111/jtm.12116
Background. Plasmodium vivax is the second most common species among cases of imported malaria diagnosed in Europe. The objective of this study is to describe the sensitivity of the parasitological tests in imported P. vivax malaria, and the impact of chemoprophylaxis and attack type (primary infection or relapse). Methods. A retrospective study included the imported vivax malaria cases admitted in a French military hospital between 2001 and 2013. The reference diagnosis method was microscopy corrected by polymerase chain reaction (PCR). Thin and thick blood films examination, quantitative buffy coat (QBC) test, and a rapid diagnostic test (RDT) had been systematically performed. PCR had been carried out for ambiguous profiles. Results. Eighty-nine cases recorded from 78 patients were included, 65 of them having recently traveled to French Guyana. Forty-two patients had properly followed chemoprophylaxis. Forty-six cases were primary infections while 43 were relapses. The sensitivity was 91% for the thin blood smear, 96% for the concentration techniques (Giemsa thick blood smear and QBC test), and 76% for the RDT. The combination of the three conventional tools has an imperfect sensitivity, both for the positive diagnosis of malaria (96%) and for the diagnosis of vivax species (80%). In 4% of the cases, the positive diagnosis was established only by the PCR. The species identification was established in 20% by the PCR. The sensibility of thin blood smear and of RDT decreased significantly with full compliance of chemoprophylaxis or primary infection, whereas the decrease of sensibility of concentration techniques was not significant. Conclusions. This study illustrates the difficulties encountered in vivax malaria diagnosis, especially in patients who properly followed chemoprophylaxis or with primary infection due to a lower parasitemia. It underlines the lack of sensitivity of RDT for P. vivax and emphasizes the need for systematically combining various diagnosis methods.
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mported malaria is defined as an infection acquired in a malaria-endemic area but diagnosed in a nonendemic country after development of clinical signs. Plasmodium vivax is the second most common species among cases of imported malaria diagnosed in Europe.1 In metropolitan France, the estimated number of imported malaria cases was 3,560 in 2011 among which 7.4% were connected to P. vivax.2 The extension of the exposure areas, the report of severe cases, and the decline of chloroquine susceptibility in Indonesia, Peru,
Corresponding Author: S´ebastien Larr´ech´e, MD, Service de ˆ Biologie M´edicale, Hopital d’Instruction des Arm´ees B´egin, 69 avenue de Paris, F-94163 Saint-Mand´e Cedex, France. E-mail: [email protected]
and Oceania justify the renewed medical interest for this species.3 The clinical presentation is nonspecific and can arise several months after the return from the exposure zone, because of relapse due to activation of dormant intrahepatic parasitic stages.4 Prompt and accurate diagnosis of the disease is essential for targeting patients requiring antimalarial treatment and for differential diagnosis with Plasmodium falciparum. Plasmodium vivax and Plasmodium ovale require a specific therapy for radical cure, combining a blood schizonticide as chloroquine and primaquine to eradicate liver hypnozoites.5 While several studies have reported epidemiological, clinical, and biological features of imported vivax malaria,1,4,6 – 11 there are few data about accuracy of © 2014 International Society of Travel Medicine, 1195-1982 Journal of Travel Medicine 2014; Volume 21 (Issue 3): 195–200
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parasitological tests in routine practice. Conventional techniques (microscopy and rapid diagnostic test, RDT) remain the first-line tools but difficulties have been reported.12,13 Molecular techniques are considered as the new gold standard but they are not yet available in all laboratories.14 Similarly, the impact of chemoprophylaxis or of attack access (ie, primary infection or relapse) remains unknown. The purpose of this study was to assess the sensitivity of conventional procedures for the diagnosis of imported vivax malaria, and the impact of chemoprophylaxis and attack type. Patients and Methods Study Design This is a descriptive monocentric retrospective study. All patients admitted at the B´egin Military Hospital, Saint-Mand´e, between January 1, 2001 and March 1, 2013, for an attack of P. vivax after staying in an endemic country were included. A case of P. vivax malaria was characterized by a signature rising fever and a positive thin blood smear with at least one typical form of P. vivax or a positive P. vivax polymerase chain reaction (PCR). The epidemiological data, the presumed exposure area, the regular use of antimalarial chemoprophylaxis, and the attack type (primary infection or relapse) have been notified from the medical file, while the parasitological tests at the admission have been extracted from the data processing system of the laboratory. The epidemiological, clinical, biological, and therapeutic characteristics of most of these patients have been described in a previous retrospective study.8
Larr´ech´e et al.
Core Malaria Pan/Pv/Pf (Core Diagnostics Ltd., Birmingham, UK). This three-band test is based on the detection of the HRP2, the pan-specific Plasmodium lactate dehydrogenate (pLDH), and the specific P. vivax LDH (PvLDH). The RDT was performed according to the manufacturer’s instructions. Based on a biologist’s decision, the PCR was performed as second intention in the following cases: negative result for the thin blood films with positivity of one concentration technique or RDT, no evidence of typical form in thin blood films because of low parasitemia, doubt regarding biparasitism, or ambiguity with P. ovale for patients returning from Africa. PCR was also performed in case of a strong clinical suspicion despite the negativity of the other four techniques. The PCR protocol consisted in four SYBR Green real-time PCR specific for each Plasmodium species (P. falciparum, P. vivax, P. ovale, and P. malariae) and was performed on the Lightcycler instrument (Roche Diagnostics, Meylan, France). Sequences used for the design of primers were 18S RNA genes of the four species (molecular target previously described15 ). Statistical Analysis Quantitative variables were expressed as median and interquartile range, while qualitative variables were measured by absolute numbers and by percentages. The chi-square test and Fisher’s exact test were used to compare data in different groups. A p value
I
S
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ORIGINAL ARTICLE
Sensitivity of Parasitological Tests in Imported Plasmodium vivax Malaria in Adults and Impact of Chemoprophylaxis and Attack Type ´ ´ e, ´ MD,∗ Christophe Rapp, MD,† Herve´ Delacour, PharmD,∗ Sebastien Larrech ´ Nancy Sanmartin, MD,∗ Cecile Ficko, MD,† Christine Bigaillon, MD,∗ Dina Andriamanantena, † ∗ ´ MD, Jean-Etienne Pilo, MD, and Audrey Merens, MD∗ ∗ Service
ˆ de Biologie M´edicale; † Service des Maladies Infectieuses et Tropicales, Hopital d’Instruction des Arm´ees B´egin, Saint-Mand´e, France DOI: 10.1111/jtm.12116
Background. Plasmodium vivax is the second most common species among cases of imported malaria diagnosed in Europe. The objective of this study is to describe the sensitivity of the parasitological tests in imported P. vivax malaria, and the impact of chemoprophylaxis and attack type (primary infection or relapse). Methods. A retrospective study included the imported vivax malaria cases admitted in a French military hospital between 2001 and 2013. The reference diagnosis method was microscopy corrected by polymerase chain reaction (PCR). Thin and thick blood films examination, quantitative buffy coat (QBC) test, and a rapid diagnostic test (RDT) had been systematically performed. PCR had been carried out for ambiguous profiles. Results. Eighty-nine cases recorded from 78 patients were included, 65 of them having recently traveled to French Guyana. Forty-two patients had properly followed chemoprophylaxis. Forty-six cases were primary infections while 43 were relapses. The sensitivity was 91% for the thin blood smear, 96% for the concentration techniques (Giemsa thick blood smear and QBC test), and 76% for the RDT. The combination of the three conventional tools has an imperfect sensitivity, both for the positive diagnosis of malaria (96%) and for the diagnosis of vivax species (80%). In 4% of the cases, the positive diagnosis was established only by the PCR. The species identification was established in 20% by the PCR. The sensibility of thin blood smear and of RDT decreased significantly with full compliance of chemoprophylaxis or primary infection, whereas the decrease of sensibility of concentration techniques was not significant. Conclusions. This study illustrates the difficulties encountered in vivax malaria diagnosis, especially in patients who properly followed chemoprophylaxis or with primary infection due to a lower parasitemia. It underlines the lack of sensitivity of RDT for P. vivax and emphasizes the need for systematically combining various diagnosis methods.
I
mported malaria is defined as an infection acquired in a malaria-endemic area but diagnosed in a nonendemic country after development of clinical signs. Plasmodium vivax is the second most common species among cases of imported malaria diagnosed in Europe.1 In metropolitan France, the estimated number of imported malaria cases was 3,560 in 2011 among which 7.4% were connected to P. vivax.2 The extension of the exposure areas, the report of severe cases, and the decline of chloroquine susceptibility in Indonesia, Peru,
Corresponding Author: S´ebastien Larr´ech´e, MD, Service de ˆ Biologie M´edicale, Hopital d’Instruction des Arm´ees B´egin, 69 avenue de Paris, F-94163 Saint-Mand´e Cedex, France. E-mail: [email protected]
and Oceania justify the renewed medical interest for this species.3 The clinical presentation is nonspecific and can arise several months after the return from the exposure zone, because of relapse due to activation of dormant intrahepatic parasitic stages.4 Prompt and accurate diagnosis of the disease is essential for targeting patients requiring antimalarial treatment and for differential diagnosis with Plasmodium falciparum. Plasmodium vivax and Plasmodium ovale require a specific therapy for radical cure, combining a blood schizonticide as chloroquine and primaquine to eradicate liver hypnozoites.5 While several studies have reported epidemiological, clinical, and biological features of imported vivax malaria,1,4,6 – 11 there are few data about accuracy of © 2014 International Society of Travel Medicine, 1195-1982 Journal of Travel Medicine 2014; Volume 21 (Issue 3): 195–200
196
parasitological tests in routine practice. Conventional techniques (microscopy and rapid diagnostic test, RDT) remain the first-line tools but difficulties have been reported.12,13 Molecular techniques are considered as the new gold standard but they are not yet available in all laboratories.14 Similarly, the impact of chemoprophylaxis or of attack access (ie, primary infection or relapse) remains unknown. The purpose of this study was to assess the sensitivity of conventional procedures for the diagnosis of imported vivax malaria, and the impact of chemoprophylaxis and attack type. Patients and Methods Study Design This is a descriptive monocentric retrospective study. All patients admitted at the B´egin Military Hospital, Saint-Mand´e, between January 1, 2001 and March 1, 2013, for an attack of P. vivax after staying in an endemic country were included. A case of P. vivax malaria was characterized by a signature rising fever and a positive thin blood smear with at least one typical form of P. vivax or a positive P. vivax polymerase chain reaction (PCR). The epidemiological data, the presumed exposure area, the regular use of antimalarial chemoprophylaxis, and the attack type (primary infection or relapse) have been notified from the medical file, while the parasitological tests at the admission have been extracted from the data processing system of the laboratory. The epidemiological, clinical, biological, and therapeutic characteristics of most of these patients have been described in a previous retrospective study.8
Larr´ech´e et al.
Core Malaria Pan/Pv/Pf (Core Diagnostics Ltd., Birmingham, UK). This three-band test is based on the detection of the HRP2, the pan-specific Plasmodium lactate dehydrogenate (pLDH), and the specific P. vivax LDH (PvLDH). The RDT was performed according to the manufacturer’s instructions. Based on a biologist’s decision, the PCR was performed as second intention in the following cases: negative result for the thin blood films with positivity of one concentration technique or RDT, no evidence of typical form in thin blood films because of low parasitemia, doubt regarding biparasitism, or ambiguity with P. ovale for patients returning from Africa. PCR was also performed in case of a strong clinical suspicion despite the negativity of the other four techniques. The PCR protocol consisted in four SYBR Green real-time PCR specific for each Plasmodium species (P. falciparum, P. vivax, P. ovale, and P. malariae) and was performed on the Lightcycler instrument (Roche Diagnostics, Meylan, France). Sequences used for the design of primers were 18S RNA genes of the four species (molecular target previously described15 ). Statistical Analysis Quantitative variables were expressed as median and interquartile range, while qualitative variables were measured by absolute numbers and by percentages. The chi-square test and Fisher’s exact test were used to compare data in different groups. A p value
