title: Swab sample transfer for point-of-care diagnostics: characterization of swab types and manual agitation methods.
abstract: BACKGROUND
  The global need for disease detection and control has increased effort to engineer point-of-care (POC) tests that are simple, robust, affordable, and non-instrumented. In many POC tests, sample collection involves swabbing the site (e.g., nose, skin), agitating the swab in a fluid to release the sample, and transferring the fluid to a device for analysis. Poor performance in sample transfer can reduce sensitivity and reproducibility.
  
  
  METHODS
  In this study, we compared bacterial release efficiency of seven swab types using manual-agitation methods typical of POC devices. Transfer efficiency was measured using quantitative PCR (qPCR) for Staphylococcus aureus under conditions representing a range of sampling scenarios: 1) spiking low-volume samples onto the swab, 2) submerging the swab in excess-volume samples, and 3) swabbing dried sample from a surface.
  
  
  RESULTS
  Excess-volume samples gave the expected recovery for most swabs (based on tip fluid capacity); a polyurethane swab showed enhanced recovery, suggesting an ability to accumulate organisms during sampling. Dry samples led to recovery of ∼20-30% for all swabs tested, suggesting that swab structure and volume is less important when organisms are applied to the outer swab surface. Low-volume samples led to the widest range of transfer efficiencies between swab types. Rayon swabs (63 µL capacity) performed well for excess-volume samples, but showed poor recovery for low-volume samples. Nylon (100 µL) and polyester swabs (27 µL) showed intermediate recovery for low-volume and excess-volume samples. Polyurethane swabs (16 µL) showed excellent recovery for all sample types. This work demonstrates that swab transfer efficiency can be affected by swab material, structure, and fluid capacity and details of the sample. Results and quantitative analysis methods from this study will assist POC assay developers in selecting appropriate swab types and transfer methods.
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, United States of America.
authors.forename: Nuttada
authors.initials: N
authors.lastname: Panpradist
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, United States of America.
authors.forename: Bhushan J
authors.initials: BJ
authors.lastname: Toley
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, United States of America.
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, United States of America.
authors.forename: Samantha
authors.initials: S
authors.lastname: Byrnes
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, United States of America.
authors.forename: Joshua R
authors.initials: JR
authors.lastname: Buser
authors.affiliation: Program in Infectious Diseases, Clinical Research Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America; Department of Pediatrics, Seattle Children's Research Institute, University of Washington, Seattle, Washington, United States of America.
authors.forename: Janet A
authors.initials: JA
authors.lastname: Englund
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington, United States of America.
authors.forename: Barry R
authors.initials: BR
authors.lastname: Lutz
mesh_terms: D003954:Diagnostic Services; D006801:Humans; D019095:Point-of-Care Systems; D012015:Reference Standards; D013048:Specimen Handling / Q000379:methods*; D013211:Staphylococcus aureus / Q000302:isolation & purification