Patent ID: 7175992

Claim:
A method for quantitatively measuring the amount of an analyte of interest in a fluid sample, comprising: a) providing a solid phase apparatus comprising a membrane strip comprising an application point, a sample capture zone and a control capture zone, wherein the sample capture zone is between the application point and the control capture zone; b) providing a sample collection apparatus containing a population of analyte binding particles, wherein the analyte binding particles are coated with an analyte binding agent, and wherein the sample collection apparatus is not in fluid communication with the solid phase apparatus; c) either: i) introducing the fluid sample into the sample collection apparatus, producing a mixed fluid sample, and subsequently introducing a buffer into the mixed fluid sample; ii) introducing a buffer into the sample collection apparatus and subsequently introducing the fluid sample; or iii) forming the fluid sample by introducing a solid into a buffer, and subsequently introducing the fluid sample into the sample collection apparatus, thereby producing a buffered, mixed fluid sample comprising contacted analyte binding particles; d) applying the buffered, mixed fluid sample to the application point of the membrane strip; e) maintaining the membrane strip under conditions which allow fluid to transport contacted analyte binding particles by capillary action through the strip to and through the sample capture zone, the sample capture zone having a sample capture reagent immobilized thereon; and allow contacted analyte binding particles to bind to the sample capture reagent; f) further maintaining the membrane strip under conditions which allow the fluid in the sample to transport contacted analyte binding particles by capillary action through the strip to and through the control capture zone, the control capture zone having a control capture reagent immobilized thereon; and allow contacted analyte binding particles to bind to the control capture reagent; g) further maintaining the membrane strip under conditions which allow the fluid in the sample to transport any contacted analyte binding particles not bound to the sample capture reagent or to the control capture reagent by capillary action beyond the control capture zone; h) determining the amount of contacted analyte binding particles in the sample capture zone and the amount of contacted analyte binding particles in the control capture zone; i) determining a corrected analyte binding particle amount from the amount of analyte binding particles in the sample capture zone and the amount of analyte binding particles in the control capture zone, wherein the amount of analyte of interest in the fluid sample is directly related to the corrected analyte binding particle amount.