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Evaluation of a density-based rapid diagnostic test for sickle cell disease in a clinical setting in Zambia.

Kumar AA, Chunda-Liyoka C, Hennek JW, Mantina H, Lee SY, Patton MR, Sambo P, Sinyangwe S, Kankasa C, Chintu C, Brugnara C, Stossel TP, Whitesides GM - PLoS ONE (2014)

Bottom Line: Of the two variations of the SCD-AMPS used, the best system (SCD-AMPS-2) demonstrated a sensitivity of 86% (82-90%) and a specificity of 60% (53-67%).Importantly, SCD-AMPS-2 was 84% (62-94%) sensitive in detecting SCD in children between 6 months and 1 year old.These health workers rated the SCD-AMPS tests to be as simple to use as lateral flow tests for malaria and HIV.

View Article: PubMed Central - PubMed

Affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America.

ABSTRACT
Although simple and low-cost interventions for sickle cell disease (SCD) exist in many developing countries, child mortality associated with SCD remains high, in part, because of the lack of access to diagnostic tests for SCD. A density-based test using aqueous multiphase systems (SCD-AMPS) is a candidate for a low-cost, point-of-care diagnostic for SCD. In this paper, the field evaluation of SCD-AMPS in a large (n = 505) case-control study in Zambia is described. Of the two variations of the SCD-AMPS used, the best system (SCD-AMPS-2) demonstrated a sensitivity of 86% (82-90%) and a specificity of 60% (53-67%). Subsequent analysis identified potential sources of false positives that include clotting, variation between batches of SCD-AMPS, and shipping conditions. Importantly, SCD-AMPS-2 was 84% (62-94%) sensitive in detecting SCD in children between 6 months and 1 year old. In addition to an evaluation of performance, an assessment of end-user operability was done with health workers in rural clinics in Zambia. These health workers rated the SCD-AMPS tests to be as simple to use as lateral flow tests for malaria and HIV.

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Related in: MedlinePlus

The sensitivity and specificity of SCD-AMPS as a function of the amount of time between collecting samples and running tests.The specificity shows a decline over each 24 hour increment, with a significant decline over 48 hours (p-value <0.0005). The sensitivity increased between the first and second time interval, but then decreased between the second and third interval (p-values <0.01). The sample size used for each time interval is provided below each bar.
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pone-0114540-g004: The sensitivity and specificity of SCD-AMPS as a function of the amount of time between collecting samples and running tests.The specificity shows a decline over each 24 hour increment, with a significant decline over 48 hours (p-value <0.0005). The sensitivity increased between the first and second time interval, but then decreased between the second and third interval (p-values <0.01). The sample size used for each time interval is provided below each bar.

Mentions: Based on our previous work [5], we set 48 hours after blood was drawn as a cutoff for inclusion in the study. To test the effect of time after collection to running tests, we also analyzed results from samples run after 48 hours. Binning test results based on whether they were run in the first, second, or third 24 hour time period after collection demonstrated a clear decline in specificity over time (Fig. 4). Both SCD-AMPS-2 and SCD-AMPS-3 showed significant (p- value  = 7.5×10−5 and 3.1×10−4) decline between samples run within 24 hours and those run after 48 hours. In both systems, sensitivity increased between the first two time intervals (p-value  = 0.0031 and 1.5×10−4) and decreased between the last two time intervals (p-value  = 2.0×10−4 and 0.0053) (Fig. 4). These results indicate that storage of the blood samples has an impact on the effectiveness of the tests. Storing erythrocytes in refrigeration can cause morphological changes that may affect density [13]. Testing on samples collected directly from a finger prick and run immediately could provide a more accurate prediction of performance of SCD-AMPS.


Evaluation of a density-based rapid diagnostic test for sickle cell disease in a clinical setting in Zambia.

Kumar AA, Chunda-Liyoka C, Hennek JW, Mantina H, Lee SY, Patton MR, Sambo P, Sinyangwe S, Kankasa C, Chintu C, Brugnara C, Stossel TP, Whitesides GM - PLoS ONE (2014)

The sensitivity and specificity of SCD-AMPS as a function of the amount of time between collecting samples and running tests.The specificity shows a decline over each 24 hour increment, with a significant decline over 48 hours (p-value <0.0005). The sensitivity increased between the first and second time interval, but then decreased between the second and third interval (p-values <0.01). The sample size used for each time interval is provided below each bar.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4260838&req=5

pone-0114540-g004: The sensitivity and specificity of SCD-AMPS as a function of the amount of time between collecting samples and running tests.The specificity shows a decline over each 24 hour increment, with a significant decline over 48 hours (p-value <0.0005). The sensitivity increased between the first and second time interval, but then decreased between the second and third interval (p-values <0.01). The sample size used for each time interval is provided below each bar.
Mentions: Based on our previous work [5], we set 48 hours after blood was drawn as a cutoff for inclusion in the study. To test the effect of time after collection to running tests, we also analyzed results from samples run after 48 hours. Binning test results based on whether they were run in the first, second, or third 24 hour time period after collection demonstrated a clear decline in specificity over time (Fig. 4). Both SCD-AMPS-2 and SCD-AMPS-3 showed significant (p- value  = 7.5×10−5 and 3.1×10−4) decline between samples run within 24 hours and those run after 48 hours. In both systems, sensitivity increased between the first two time intervals (p-value  = 0.0031 and 1.5×10−4) and decreased between the last two time intervals (p-value  = 2.0×10−4 and 0.0053) (Fig. 4). These results indicate that storage of the blood samples has an impact on the effectiveness of the tests. Storing erythrocytes in refrigeration can cause morphological changes that may affect density [13]. Testing on samples collected directly from a finger prick and run immediately could provide a more accurate prediction of performance of SCD-AMPS.

Bottom Line: Of the two variations of the SCD-AMPS used, the best system (SCD-AMPS-2) demonstrated a sensitivity of 86% (82-90%) and a specificity of 60% (53-67%).Importantly, SCD-AMPS-2 was 84% (62-94%) sensitive in detecting SCD in children between 6 months and 1 year old.These health workers rated the SCD-AMPS tests to be as simple to use as lateral flow tests for malaria and HIV.

View Article: PubMed Central - PubMed

Affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States of America.

ABSTRACT
Although simple and low-cost interventions for sickle cell disease (SCD) exist in many developing countries, child mortality associated with SCD remains high, in part, because of the lack of access to diagnostic tests for SCD. A density-based test using aqueous multiphase systems (SCD-AMPS) is a candidate for a low-cost, point-of-care diagnostic for SCD. In this paper, the field evaluation of SCD-AMPS in a large (n = 505) case-control study in Zambia is described. Of the two variations of the SCD-AMPS used, the best system (SCD-AMPS-2) demonstrated a sensitivity of 86% (82-90%) and a specificity of 60% (53-67%). Subsequent analysis identified potential sources of false positives that include clotting, variation between batches of SCD-AMPS, and shipping conditions. Importantly, SCD-AMPS-2 was 84% (62-94%) sensitive in detecting SCD in children between 6 months and 1 year old. In addition to an evaluation of performance, an assessment of end-user operability was done with health workers in rural clinics in Zambia. These health workers rated the SCD-AMPS tests to be as simple to use as lateral flow tests for malaria and HIV.

Show MeSH
Related in: MedlinePlus