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Field trial of three different Plasmodium vivax-detecting rapid diagnostic tests with and without evaporative cool box storage in Afghanistan.

Mikhail AF, Leslie TJ, Mayan MI, Zekria R, Mohammad N, Hasanzai MA, Safi N, Whitty CJ, Rowland M - Malar. J. (2011)

Bottom Line: Room temperature storage of SDBPfPv led to a high proportion of invalid results (17%), which reduced to 10% in the ECB.The CSPfPv test proved unsuitable owing to its reduced sensitivity at a parasitaemia below 5,000/μL (affecting 43% of study samples).ECB storage reduced the proportion of invalid results for the SDBPfPv test, but surprisingly had no impact on RDT sensitivity at low parasitaemia.

View Article: PubMed Central - HTML - PubMed

Affiliation: London School of Hygiene & Tropical Medicine, London, UK. Amy.Mikhail@lshtm.ac.uk

ABSTRACT

Background: Accurate parasitological diagnosis of malaria is essential for targeting treatment where more than one species coexist. In this study, three rapid diagnostic tests (RDTs) (AccessBio CareStart (CSPfPan), CareStart PfPv (CSPfPv) and Standard Diagnostics Bioline (SDBPfPv)) were evaluated for their ability to detect natural Plasmodium vivax infections in a basic clinic setting. The potential for locally made evaporative cooling boxes (ECB) to protect the tests from heat damage in high summer temperatures was also investigated.

Methods: Venous blood was drawn from P. vivax positive patients in Jalalabad, Afghanistan and tested against a panel of six RDTs. The panel comprised two of each test type; one group was stored at room temperature and the other in an ECB. RDT results were evaluated against a consensus gold standard based on two double-read reference slides and PCR. The sensitivity, specificity and a measure of global performance for each test were determined and stratified by parasitaemia level and storage condition.

Results: In total, 306 patients were recruited, of which 284 were positive for P. vivax, one for Plasmodium malariae and none for Plasmodium falciparum; 21 were negative. All three RDTs were specific for malaria. The sensitivity and global performance index for each test were as follows: CSPfPan [98.6%, 95.1%], CSPfPv [91.9%, 90.5%] and SDBPfPv [96.5%, 82.9%], respectively. CSPfPv was 16% less sensitive to a parasitaemia below 5,000/μL. Room temperature storage of SDBPfPv led to a high proportion of invalid results (17%), which reduced to 10% in the ECB. Throughout the testing period, the ECB maintained ~8°C reduction over ambient temperatures and never exceeded 30°C.

Conclusions: Of the three RDTs, the CSPfPan test was the most consistent and reliable, rendering it appropriate for this P. vivax predominant region. The CSPfPv test proved unsuitable owing to its reduced sensitivity at a parasitaemia below 5,000/μL (affecting 43% of study samples). Although the SDBPfPv device was more sensitive than the CSPfPv test, its invalid rate was unacceptably high. ECB storage reduced the proportion of invalid results for the SDBPfPv test, but surprisingly had no impact on RDT sensitivity at low parasitaemia.

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Related in: MedlinePlus

Evaporative cooler box with drip tray.
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Figure 1: Evaporative cooler box with drip tray.

Mentions: An evaporative cooling box adapted from designs tested by Bell and others in Cambodia [31] was chosen for this study (Figure 1). Pre-study enquiries indicated that health centres would prefer a portable box to underground pits, since the latter would require quite significant building work and be potentially disruptive to the layout of the clinic. Evaporative coolers are appropriate technology storage solutions which do not require electricity or much maintenance to run. The system consists of an enclosed metal box (the storage space) with extended sides to form a tray on the top capable of holding water. The box is covered in hessian, with material wicks connecting the hessian cover to the water filled tray. Water transfers by capillary action via the wicks to the hessian cover. Water evaporates off the hessian cover, cooling the metal box and its contents.


Field trial of three different Plasmodium vivax-detecting rapid diagnostic tests with and without evaporative cool box storage in Afghanistan.

Mikhail AF, Leslie TJ, Mayan MI, Zekria R, Mohammad N, Hasanzai MA, Safi N, Whitty CJ, Rowland M - Malar. J. (2011)

Evaporative cooler box with drip tray.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3141591&req=5

Figure 1: Evaporative cooler box with drip tray.
Mentions: An evaporative cooling box adapted from designs tested by Bell and others in Cambodia [31] was chosen for this study (Figure 1). Pre-study enquiries indicated that health centres would prefer a portable box to underground pits, since the latter would require quite significant building work and be potentially disruptive to the layout of the clinic. Evaporative coolers are appropriate technology storage solutions which do not require electricity or much maintenance to run. The system consists of an enclosed metal box (the storage space) with extended sides to form a tray on the top capable of holding water. The box is covered in hessian, with material wicks connecting the hessian cover to the water filled tray. Water transfers by capillary action via the wicks to the hessian cover. Water evaporates off the hessian cover, cooling the metal box and its contents.

Bottom Line: Room temperature storage of SDBPfPv led to a high proportion of invalid results (17%), which reduced to 10% in the ECB.The CSPfPv test proved unsuitable owing to its reduced sensitivity at a parasitaemia below 5,000/μL (affecting 43% of study samples).ECB storage reduced the proportion of invalid results for the SDBPfPv test, but surprisingly had no impact on RDT sensitivity at low parasitaemia.

View Article: PubMed Central - HTML - PubMed

Affiliation: London School of Hygiene & Tropical Medicine, London, UK. Amy.Mikhail@lshtm.ac.uk

ABSTRACT

Background: Accurate parasitological diagnosis of malaria is essential for targeting treatment where more than one species coexist. In this study, three rapid diagnostic tests (RDTs) (AccessBio CareStart (CSPfPan), CareStart PfPv (CSPfPv) and Standard Diagnostics Bioline (SDBPfPv)) were evaluated for their ability to detect natural Plasmodium vivax infections in a basic clinic setting. The potential for locally made evaporative cooling boxes (ECB) to protect the tests from heat damage in high summer temperatures was also investigated.

Methods: Venous blood was drawn from P. vivax positive patients in Jalalabad, Afghanistan and tested against a panel of six RDTs. The panel comprised two of each test type; one group was stored at room temperature and the other in an ECB. RDT results were evaluated against a consensus gold standard based on two double-read reference slides and PCR. The sensitivity, specificity and a measure of global performance for each test were determined and stratified by parasitaemia level and storage condition.

Results: In total, 306 patients were recruited, of which 284 were positive for P. vivax, one for Plasmodium malariae and none for Plasmodium falciparum; 21 were negative. All three RDTs were specific for malaria. The sensitivity and global performance index for each test were as follows: CSPfPan [98.6%, 95.1%], CSPfPv [91.9%, 90.5%] and SDBPfPv [96.5%, 82.9%], respectively. CSPfPv was 16% less sensitive to a parasitaemia below 5,000/μL. Room temperature storage of SDBPfPv led to a high proportion of invalid results (17%), which reduced to 10% in the ECB. Throughout the testing period, the ECB maintained ~8°C reduction over ambient temperatures and never exceeded 30°C.

Conclusions: Of the three RDTs, the CSPfPan test was the most consistent and reliable, rendering it appropriate for this P. vivax predominant region. The CSPfPv test proved unsuitable owing to its reduced sensitivity at a parasitaemia below 5,000/μL (affecting 43% of study samples). Although the SDBPfPv device was more sensitive than the CSPfPv test, its invalid rate was unacceptably high. ECB storage reduced the proportion of invalid results for the SDBPfPv test, but surprisingly had no impact on RDT sensitivity at low parasitaemia.

Show MeSH
Related in: MedlinePlus