The water extract is wicked through a reagent zone, which contains antibodies specific for CP4 conjugated to colored particles. If CP4 is present, it will be captured by the conjugated antibodies. The CP4-antibody-particle complex is then wicked onto a membrane which contains a zone of antibody specific for CP4. This zone captures the complex allowing the particles to concentrate and form a visible line. If no CP4 is present, no line will form. The membrane also contains a control zone where an immune complex present in the reagent zone is captured by an antibody, forming a visible line. The control line will always form regardless of the presence of CP4, ensuring the strip is working properly.