The Typhoid Fever Surveillance in Africa Program: Geospatial Sampling Frames for Household-based Studies: Lessons Learned From a Multicountry Surveillance Network in Senegal, South Africa, and Sudan. (30th October 2019)

• Record Type: Journal Article
• Authors: Baker, Stephen; Ali, Mohammad; Deerin, Jessica Fung; Eltayeb, Muna Ahmed; Cruz Espinoza, Ligia Maria; Gasmelseed, Nagla; Im, Justin; Panzner, Ursula; Kalckreuth, Vera V; Keddy, Karen H; Pak, Gi Deok; Park, Jin Kyung; Park, Se Eun; Sooka, Arvinda; Sow, Amy Gassama; Tall, Adama; Luby, Stephen; Meyer, Christian G; Marks, Florian
• Is Part Of: Clinical infectious diseases. Volume 69(2019)Supplement 6
• Page Start: S474
• Page End: S482
• Publication Date: 2019-10-30
• Subjects: satellite imagery -- geospatial sampling frame -- positional accuracy -- sub-Saharan Africa; Communicable diseases -- Periodicals; 616.905
• DOI: 10.1093/cid/ciz755
• Languages: English
• ISSNs: 1058-4838

Abstract

Abstract: Background: Robust household sampling, commonly applied for population-based investigations, requires sampling frames or household lists to minimize selection bias. We have applied Google Earth Pro satellite imagery to constitute structure-based sampling frames at sites in Pikine, Senegal; Pietermaritzburg, South Africa; and Wad-Medani, Sudan. Here we present our experiences in using this approach and findings from assessing its applicability by determining positional accuracy. Methods: Printouts of satellite imagery combined with Global Positioning System receivers were used to locate and to verify the locations of sample structures (simple random selection; weighted-stratified sampling). Positional accuracy was assessed by study site and administrative subareas by calculating normalized distances (meters) between coordinates taken from the sampling frame and on the ground using receivers. A higher accuracy in conjunction with smaller distances was assumed. Kruskal-Wallis and Dunn multiple pairwise comparisons were performed to evaluate positional accuracy by setting and by individual surveyor in Pietermaritzburg. Results: The median normalized distances and interquartile ranges were 0.05 and 0.03–0.08 in Pikine, 0.09 and 0.05–0.19 in Pietermaritzburg, and 0.05 and 0.00–0.10 in Wad-Medani, respectively. Root mean square errors were 0.08 in Pikine, 0.42 in Pietermaritzburg, and 0.17 in Wad-Medani. Kruskal-Wallis and Dunn comparisons indicated significant differences by low- and high-density setting and interviewers who performed the presented approach with high accuracy compared to interviewers with poor accuracy. Conclusions: The geospatial approach presented minimizes systematic errors and increases robustness and representativeness of a sample. However, the findings imply that this approach may not be applicable at all sites and settings; its success also depends on skills of surveyors working with aerial data. Methodological modifications are required, especially for resource-challenged sites that may be affected by constraints in data availability and area size.