Malaria Rapid Diagnostic Test as Point-of-Care Test
Malaria Rapid Diagnostic Test as Point-of-Care Test
The VIKIA® Malaria Ag Pf/Pan (IMACCESS/bioMérieux, Lyon, France) is a test based on immunochromatographic technology for detecting P. falciparum and other species of Plasmodium (P. vivax, P. malariae and P. ovale). This test is a ready-to-use cassette device, requiring the operator to transfer 5 μL of blood in the sample well with an appropriate device supplied in the kit, add five drops of the lysis buffer in the buffer well and read the results visually after 20 minutes (see Additional files 1 and 2 http://www.malariajournal.com/content/14/1/114/additional; SF1 Quick guide for using the VIKIA® Malaria Ag Pf/Pan RDT and SF2 Package Insert of the VIKIA® Malaria Ag Pf/Pan RDT).
Seven communes in Kampot Province (Cambodia) were selected for this multisite, blinded study. Four different end-user profiles were considered as representative of the typical malaria RDTs end-users found in malaria-endemic areas: health medical centre staff, private physician, community health worker (village malaria worker (VMW)) and private pharmacist. Five individuals of each end-user profiles were enrolled in the study, as presented in Figure 1 and Table 1.
(Enlarge Image)
Figure 1.
Location of the selected end-users, Kampot Province, Cambodia.
Three types of sample (negative, low positive, high positive) were tested in replicates of four, corresponding to a panel of 20 aliquots, as followed: one negative sample, one low positive sample at 200 parasites of P. falciparum/μL, one low positive sample at 200 parasites of P. vivax/μL, one high positive sample at 2,000 parasites of P. falciparum/μL and one high positive sample at 2,000 parasites of P. vivax/μL.
The set of 20 coded aliquots was prepared according to the Standard Operating Procedures (SOP) developed in the Methods Manual for Laboratory QC Testing of Malaria RDTs (Version 7, June 2014) and codified as described in Table 2. Briefly, the preparation of positive parasite samples was performed in three steps: i) blood sample collection from consenting malaria patients (strong positive detection by RDT and parasite density > 2,000 parasites/μL of blood by microscopy); ii) collection of parasite-free (controlled by PCR) and virus-free (controlled by serological screening for HIV, hepatitis B and hepatitis C infections) blood from the Phnom Penh blood bank and, iii) dilution of the parasite-positive bloods in low (200 parasites/μL) and high (2,000 parasites/μL) parasite densities and preparation of parasite-negative QC samples and aliquoting (50 μL) in cryotubes frozen at −80°C.
Frozen calibrated blood aliquots were transported at −80°C in a portable freezer running on 12 V (works with a cigarette lighter in a car). Defrosting was performed by the research team just before its use by the end-user (Figure 2).
(Enlarge Image)
Figure 2.
Flow chart of the use in field conditions of well-characterized and calibrated blood samples (set of 20 aliquots) by selected end-users, Kampot Province, Cambodia.
Before the start of the study, the research team explained the study objective to all end-users. Testing was performed directly by the end-users without any practical training on the VIKIA® Malaria Ag Pf/Pan kit. The only instructions for use were available within the quick guide and the package insert provided in the VIKIA® Malaria Ag Pf/Pan kit (see Additional files 1 and 2 http://www.malariajournal.com/content/14/1/114/additional).
The research team performed a quality control assessment of the set of the 20 aliquots at three different times (at the start, middle and end of the study), to confirm the good quality of the aliquots distributed to the users and to verify that no degradation occurred during transport or storage that could affect the expected results.
Data were recorded and analysed using Excel software and MedCalc (MedCalc Software, Belgium). The Chi-squared test was used to compare the proportion of positive results among end-users. A P-value <0.05 was considered to indicate statistical significance.
Methods
VIKIA® Malaria Ag Pf/Pan Test
The VIKIA® Malaria Ag Pf/Pan (IMACCESS/bioMérieux, Lyon, France) is a test based on immunochromatographic technology for detecting P. falciparum and other species of Plasmodium (P. vivax, P. malariae and P. ovale). This test is a ready-to-use cassette device, requiring the operator to transfer 5 μL of blood in the sample well with an appropriate device supplied in the kit, add five drops of the lysis buffer in the buffer well and read the results visually after 20 minutes (see Additional files 1 and 2 http://www.malariajournal.com/content/14/1/114/additional; SF1 Quick guide for using the VIKIA® Malaria Ag Pf/Pan RDT and SF2 Package Insert of the VIKIA® Malaria Ag Pf/Pan RDT).
Participating Communes and End-users
Seven communes in Kampot Province (Cambodia) were selected for this multisite, blinded study. Four different end-user profiles were considered as representative of the typical malaria RDTs end-users found in malaria-endemic areas: health medical centre staff, private physician, community health worker (village malaria worker (VMW)) and private pharmacist. Five individuals of each end-user profiles were enrolled in the study, as presented in Figure 1 and Table 1.
(Enlarge Image)
Figure 1.
Location of the selected end-users, Kampot Province, Cambodia.
Sample Characteristics
Three types of sample (negative, low positive, high positive) were tested in replicates of four, corresponding to a panel of 20 aliquots, as followed: one negative sample, one low positive sample at 200 parasites of P. falciparum/μL, one low positive sample at 200 parasites of P. vivax/μL, one high positive sample at 2,000 parasites of P. falciparum/μL and one high positive sample at 2,000 parasites of P. vivax/μL.
The set of 20 coded aliquots was prepared according to the Standard Operating Procedures (SOP) developed in the Methods Manual for Laboratory QC Testing of Malaria RDTs (Version 7, June 2014) and codified as described in Table 2. Briefly, the preparation of positive parasite samples was performed in three steps: i) blood sample collection from consenting malaria patients (strong positive detection by RDT and parasite density > 2,000 parasites/μL of blood by microscopy); ii) collection of parasite-free (controlled by PCR) and virus-free (controlled by serological screening for HIV, hepatitis B and hepatitis C infections) blood from the Phnom Penh blood bank and, iii) dilution of the parasite-positive bloods in low (200 parasites/μL) and high (2,000 parasites/μL) parasite densities and preparation of parasite-negative QC samples and aliquoting (50 μL) in cryotubes frozen at −80°C.
Frozen calibrated blood aliquots were transported at −80°C in a portable freezer running on 12 V (works with a cigarette lighter in a car). Defrosting was performed by the research team just before its use by the end-user (Figure 2).
(Enlarge Image)
Figure 2.
Flow chart of the use in field conditions of well-characterized and calibrated blood samples (set of 20 aliquots) by selected end-users, Kampot Province, Cambodia.
Training
Before the start of the study, the research team explained the study objective to all end-users. Testing was performed directly by the end-users without any practical training on the VIKIA® Malaria Ag Pf/Pan kit. The only instructions for use were available within the quick guide and the package insert provided in the VIKIA® Malaria Ag Pf/Pan kit (see Additional files 1 and 2 http://www.malariajournal.com/content/14/1/114/additional).
Quality Control Assessment of the Calibrated Aliquots
The research team performed a quality control assessment of the set of the 20 aliquots at three different times (at the start, middle and end of the study), to confirm the good quality of the aliquots distributed to the users and to verify that no degradation occurred during transport or storage that could affect the expected results.
Statistical Analysis
Data were recorded and analysed using Excel software and MedCalc (MedCalc Software, Belgium). The Chi-squared test was used to compare the proportion of positive results among end-users. A P-value <0.05 was considered to indicate statistical significance.
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