title: Correlation of serum and dried blood spot results for quantitation of Schistosoma circulating anodic antigen: a proof of principle.
abstract: Circulating anodic antigen (CAA) testing is a powerful, increasingly-used tool for diagnosis of active schistosome infection. We sought to determine the feasibility and reliability of measuring CAA in blood spots collected on Whatman 903 protein saver cards, which are the predominant filter papers used worldwide for dried blood spot (DBS) research and clinical care. CAA was eluted from blood spots collected from 19 individuals onto Whatman 903 cards in Mwanza, Tanzania, and the assay was optimized to achieve CAA ratios comparable to those obtained from the spots' corresponding serum samples. The optimized assay was then used to determine the correlation of serum samples (n=16) with DBS from cards that had been stored for 8 years at ambient temperature. Using a DBS volume equivalent to approximately four times the quantity of serum, CAA testing in DBS had a sensitivity of 76% and a specificity of 79% compared to CAA testing in serum. CAA testing was reliable in samples eluted from Whatman 903 cards that had been stored for 8 years at ambient temperature. The overall kappa coefficient was 0.53 (standard error 0.17, p<0.001). We conclude that CAA can be reliably and accurately measured in DBS collected onto the filter paper that is most commonly used for clinical care and research, and that can be stored from prolonged periods of time. This finding opens new avenues for future work among more than 700million individuals living in areas worldwide in which schistosomes are endemic.
authors.affiliation: Center for Global Health, Weill Cornell Medical College, 402 E. 67th Street, Second Floor, New York, NY, USA; Department of Medicine, Bugando Medical Centre, Box 1370, Mwanza, Tanzania. Electronic address: jna2002@med.cornell.edu.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Downs
authors.affiliation: Department of Molecular Cell Biology, Leiden University Medical Center, Postzone S1-P, Postbus 9600, 2300 RC Leiden, The Netherlands. Electronic address: p.corstjens@lumc.nl.
authors.forename: Paul L A M
authors.initials: PL
authors.lastname: Corstjens
authors.affiliation: National Institute for Medical Research-Mwanza Research Centre, Box 1462, Mwanza, Tanzania. Electronic address: juliusmngara@yahoo.com.
authors.forename: Julius
authors.initials: J
authors.lastname: Mngara
authors.affiliation: National Institute for Medical Research-Mwanza Research Centre, Box 1462, Mwanza, Tanzania. Electronic address: peter.lutonja@mitu.or.tz.
authors.forename: Peter
authors.initials: P
authors.lastname: Lutonja
authors.affiliation: National Institute for Medical Research-Mwanza Research Centre, Box 1462, Mwanza, Tanzania. Electronic address: rrisingo@yahoo.co.uk.
authors.forename: Raphael
authors.initials: R
authors.lastname: Isingo
authors.affiliation: National Institute for Medical Research-Mwanza Research Centre, Box 1462, Mwanza, Tanzania. Electronic address: urassamark@yahoo.co.uk.
authors.forename: Mark
authors.initials: M
authors.lastname: Urassa
authors.affiliation: Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands. Electronic address: d.kornelis@lumc.nl.
authors.forename: Dieuwke
authors.initials: D
authors.lastname: Kornelis
authors.affiliation: Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands. Electronic address: G.J.van_Dam@lumc.nl.
authors.forename: Govert J
authors.initials: GJ
authors.lastname: van Dam
mesh_terms: D000818:Animals; D000947:Antigens, Helminth / Q000097:blood*; D059788:Dried Blood Spot Testing / Q000379:methods*; D006801:Humans; D015203:Reproducibility of Results; D012547:Schistosoma / Q000276:immunology*
chemical_list: D000947:Antigens, Helminth
keywords: Circulating anodic antigen; Diagnostics; Dried blood spot; Schistosomiasis; Serum