title: Reply to Ng and Tan.
authors.forename: Sue
authors.initials: S
authors.lastname: Mavedzenge Napierala
authors.forename: Rachel
authors.initials: R
authors.lastname: Baggaley
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Corbett
mesh_terms: D019411:Clinical Laboratory Techniques / Q000379:methods*; D015658:HIV Infections / Q000175:diagnosis* / Q000517:prevention & control*; D006801:Humans; D012646:Self Administration / Q000379:methods*