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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

Daytime temperature and humidity in the evaporative cooler box. This box was installed in a room at the Malaria Reference Centre, Jalal Abad and the pre-trial data shown in this image was recorded from mid-May to early June 2009. Relative humidity outside the box is represented by the blue shaded area; room temperature is indicated by the red line and temperature inside the box is indicated by the blue line.
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Figure 3: Daytime temperature and humidity in the evaporative cooler box. This box was installed in a room at the Malaria Reference Centre, Jalal Abad and the pre-trial data shown in this image was recorded from mid-May to early June 2009. Relative humidity outside the box is represented by the blue shaded area; room temperature is indicated by the red line and temperature inside the box is indicated by the blue line.

Mentions: The evaporative cooler was examined for its capacity to protect tests, defined as the ability of the box to maintain an internal temperature of less than 30°C, when the ambient temperature is above 30°C. Initially, temperature differentials and relative humidity were assessed over an eight-day period prior to the start of the study. The box was placed in a typical un-cooled room inside the study clinic. Ambient temperature in the room ranged from 30 to 33°C, whereas temperature inside the EC box ranged from 20 to 26°C. Thereafter, temperature differentials in relation to relative humidity were continuously monitored during clinic hours (from eight in the morning until two in the afternoon) for the duration of the study (Figure 3). Temperature inside the box varied over a wider range than ambient temperature in the room and this was positively correlated with relative humidity (R2 = 0.8, P = < 0.0001). Despite this variation, EC box temperature remained significantly lower than room temperature at all times; the average temperature differential was 8°C and ranged from 4 to 14°C. The highest ambient temperature (37°C) was recorded mid-study on 8th July, at which time the corresponding temperature in the EC box was 23°C.


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)

Daytime temperature and humidity in the evaporative cooler box. This box was installed in a room at the Malaria Reference Centre, Jalal Abad and the pre-trial data shown in this image was recorded from mid-May to early June 2009. Relative humidity outside the box is represented by the blue shaded area; room temperature is indicated by the red line and temperature inside the box is indicated by the blue line.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Daytime temperature and humidity in the evaporative cooler box. This box was installed in a room at the Malaria Reference Centre, Jalal Abad and the pre-trial data shown in this image was recorded from mid-May to early June 2009. Relative humidity outside the box is represented by the blue shaded area; room temperature is indicated by the red line and temperature inside the box is indicated by the blue line.
Mentions: The evaporative cooler was examined for its capacity to protect tests, defined as the ability of the box to maintain an internal temperature of less than 30°C, when the ambient temperature is above 30°C. Initially, temperature differentials and relative humidity were assessed over an eight-day period prior to the start of the study. The box was placed in a typical un-cooled room inside the study clinic. Ambient temperature in the room ranged from 30 to 33°C, whereas temperature inside the EC box ranged from 20 to 26°C. Thereafter, temperature differentials in relation to relative humidity were continuously monitored during clinic hours (from eight in the morning until two in the afternoon) for the duration of the study (Figure 3). Temperature inside the box varied over a wider range than ambient temperature in the room and this was positively correlated with relative humidity (R2 = 0.8, P = < 0.0001). Despite this variation, EC box temperature remained significantly lower than room temperature at all times; the average temperature differential was 8°C and ranged from 4 to 14°C. The highest ambient temperature (37°C) was recorded mid-study on 8th July, at which time the corresponding temperature in the EC box was 23°C.

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