A flexible planar patch suitable for application to a patient's skin is provided. The planar patch comprises a capture layer (100) and a cover layer (200). The capture layer (100) comprises an analyte capture zone (105) and a fastener zone (104). The analyte capture zone (105) consists of a first water permeable material comprising a ligand capable of binding specifically to an analyte. The fastener zone (104) is impermeable to water and/or delimited from said analyte capture zone by a water impermeable barrier zone (108) and comprises an adhesive (133) capable of fastening the capture layer (100) removably to a surface. The cover layer comprises an adhesive (233) capable of fastening the cover layer (200) removably to the capture layer (100). In addition, a kit for assembly of the patch and a diagnostic method using the patch are provided.
