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Estimating malaria parasite prevalence from community surveys in Uganda: a comparison of microscopy, rapid diagnostic tests and polymerase chain reaction.

Nankabirwa JI, Yeka A, Arinaitwe E, Kigozi R, Drakeley C, Kamya MR, Greenhouse B, Rosenthal PJ, Dorsey G, Staedke SG - Malar. J. (2015)

Bottom Line: The sensitivity of RDTs was similar across the three sites (range 77.2-82.8%), was consistently higher than microscopy (p < 0.001 for all pairwise comparisons), and decreased with increasing age.Relative differences in parasite prevalence across age groups and study years differed for RDTs compared to microscopy and PCR.It is important to consider the effects of these parameters when designing and interpreting community-based surveys.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda. jnankabirwa@yahoo.co.uk.

ABSTRACT

Background: Household surveys are important tools for monitoring the malaria disease burden and measuring impact of malaria control interventions with parasite prevalence as the primary metric. However, estimates of parasite prevalence are dependent on a number of factors including the method used to detect parasites, age of the population sampled, and level of immunity. To better understand the influence of diagnostics, age, and endemicity on estimates of parasite prevalence and how these change over time, community-based surveys were performed for two consecutive years in three settings and the sensitivities of microscopy and immunochromatographic rapid diagnostic tests (RDTs) were assessed, considering polymerase chain reaction (PCR) as the gold standard.

Methods: Surveys were conducted over the same two-month period in 2012 and 2013 in each of three sub-counties in Uganda: Nagongera in Tororo District (January-February), Walukuba in Jinja District (March-April), and Kihihi in Kanungu District (May-June). In each sub-county, 200 households were randomly enrolled and a household questionnaire capturing information on demographics, use of malaria prevention methods, and proxy indicators of wealth was administered to the head of the household. Finger-prick blood samples were obtained for RDTs, measurement of hemoglobin, thick and thin blood smears, and to store samples on filter paper.

Results: A total of 1200 households were surveyed and 4433 participants were included in the analysis. Compared to PCR, the sensitivity of microscopy was low (65.3% in Nagongera, 49.6% in Walukuba and 40.9% in Kihihi) and decreased with increasing age. The specificity of microscopy was over 98% at all sites and did not vary with age or year. Relative differences in parasite prevalence across different age groups, study sites, and years were similar for microscopy and PCR. The sensitivity of RDTs was similar across the three sites (range 77.2-82.8%), was consistently higher than microscopy (p < 0.001 for all pairwise comparisons), and decreased with increasing age. The specificity of RDTs was lower than microscopy (76.3% in Nagongera, 86.3% in Walukuba, and 83.5% in Kihihi) and varied significantly by year and age. Relative differences in parasite prevalence across age groups and study years differed for RDTs compared to microscopy and PCR.

Conclusion: Malaria prevalence estimates varied with diagnostic test, age, and transmission intensity. It is important to consider the effects of these parameters when designing and interpreting community-based surveys.

No MeSH data available.


Related in: MedlinePlus

Sensitivity of microscopy and RDTs by age-groups at the three study sites
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Fig2: Sensitivity of microscopy and RDTs by age-groups at the three study sites

Mentions: The sensitivity of microscopy was higher in Nagongera (65.3 %) compared to Walukuba (49.6 %, p < 0.001) and Kihihi (40.9 %, p < 0.001), and decreased from 2012 to 2013 in Nagongera (p < 0.001, Table 2). Importantly, sensitivity of microscopy fluctuated by a factor of 2 with age. In Nagongera and Kihihi, sensitivity increased until approximately 9 years of age, then decreased with increasing age; in Walukuba a linear decrease with age was observed, with granularity of this relationship possibly limited by the lower number of positive samples at this site (Fig. 2). The specificity of microscopy was over 98 % at all three sites in both years of the study and did not change appreciably with age (Table 2; Fig. 2).Table 2


Estimating malaria parasite prevalence from community surveys in Uganda: a comparison of microscopy, rapid diagnostic tests and polymerase chain reaction.

Nankabirwa JI, Yeka A, Arinaitwe E, Kigozi R, Drakeley C, Kamya MR, Greenhouse B, Rosenthal PJ, Dorsey G, Staedke SG - Malar. J. (2015)

Sensitivity of microscopy and RDTs by age-groups at the three study sites
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4696244&req=5

Fig2: Sensitivity of microscopy and RDTs by age-groups at the three study sites
Mentions: The sensitivity of microscopy was higher in Nagongera (65.3 %) compared to Walukuba (49.6 %, p < 0.001) and Kihihi (40.9 %, p < 0.001), and decreased from 2012 to 2013 in Nagongera (p < 0.001, Table 2). Importantly, sensitivity of microscopy fluctuated by a factor of 2 with age. In Nagongera and Kihihi, sensitivity increased until approximately 9 years of age, then decreased with increasing age; in Walukuba a linear decrease with age was observed, with granularity of this relationship possibly limited by the lower number of positive samples at this site (Fig. 2). The specificity of microscopy was over 98 % at all three sites in both years of the study and did not change appreciably with age (Table 2; Fig. 2).Table 2

Bottom Line: The sensitivity of RDTs was similar across the three sites (range 77.2-82.8%), was consistently higher than microscopy (p < 0.001 for all pairwise comparisons), and decreased with increasing age.Relative differences in parasite prevalence across age groups and study years differed for RDTs compared to microscopy and PCR.It is important to consider the effects of these parameters when designing and interpreting community-based surveys.

View Article: PubMed Central - PubMed

Affiliation: Department of Medicine, Makerere University College of Health Sciences, Kampala, Uganda. jnankabirwa@yahoo.co.uk.

ABSTRACT

Background: Household surveys are important tools for monitoring the malaria disease burden and measuring impact of malaria control interventions with parasite prevalence as the primary metric. However, estimates of parasite prevalence are dependent on a number of factors including the method used to detect parasites, age of the population sampled, and level of immunity. To better understand the influence of diagnostics, age, and endemicity on estimates of parasite prevalence and how these change over time, community-based surveys were performed for two consecutive years in three settings and the sensitivities of microscopy and immunochromatographic rapid diagnostic tests (RDTs) were assessed, considering polymerase chain reaction (PCR) as the gold standard.

Methods: Surveys were conducted over the same two-month period in 2012 and 2013 in each of three sub-counties in Uganda: Nagongera in Tororo District (January-February), Walukuba in Jinja District (March-April), and Kihihi in Kanungu District (May-June). In each sub-county, 200 households were randomly enrolled and a household questionnaire capturing information on demographics, use of malaria prevention methods, and proxy indicators of wealth was administered to the head of the household. Finger-prick blood samples were obtained for RDTs, measurement of hemoglobin, thick and thin blood smears, and to store samples on filter paper.

Results: A total of 1200 households were surveyed and 4433 participants were included in the analysis. Compared to PCR, the sensitivity of microscopy was low (65.3% in Nagongera, 49.6% in Walukuba and 40.9% in Kihihi) and decreased with increasing age. The specificity of microscopy was over 98% at all sites and did not vary with age or year. Relative differences in parasite prevalence across different age groups, study sites, and years were similar for microscopy and PCR. The sensitivity of RDTs was similar across the three sites (range 77.2-82.8%), was consistently higher than microscopy (p < 0.001 for all pairwise comparisons), and decreased with increasing age. The specificity of RDTs was lower than microscopy (76.3% in Nagongera, 86.3% in Walukuba, and 83.5% in Kihihi) and varied significantly by year and age. Relative differences in parasite prevalence across age groups and study years differed for RDTs compared to microscopy and PCR.

Conclusion: Malaria prevalence estimates varied with diagnostic test, age, and transmission intensity. It is important to consider the effects of these parameters when designing and interpreting community-based surveys.

No MeSH data available.


Related in: MedlinePlus