Competitive lateral flow assay

A method of detecting a target molecule in a liquid sample having a first volume, comprising:

• providing a diagnostic system comprising a diagnostic strip, the diagnostic strip comprising:
• an elongate substrate having a first end and a second end;
• a first layer supported on the elongate substrate proximate to the first end for receiving, absorbing, and filtering the liquid sample;
• a second layer comprising a conjugate pad supported on the elongate substrate downstream of the first layer for storing antibody conjugates;
• a first spacer layer supported on the elongate substrate downstream of the second layer;
• and
• a third layer supported on the elongate substrate downstream of the first spacer layer, wherein the third layer comprises a test region and a control region;
• applying the liquid sample to said first layer, wherein the volume of the liquid sample is insufficient to overflow the first spacer layer;
• applying a buffer to said first layer after said applying the liquid sample to said first layer, the buffer having a second volume sufficient to cause the liquid sample to flow from the first spacer layer to the third layer;
• and
• analyzing the test and control regions in said third layer to determine whether the target material is present in the liquid sample and/or a quantity of the target material in the liquid sample.