Systems and methods for identifying rare cells

A reagent system for fixing cells, the reagent system comprising:

• a first fixing buffer comprising:
• 3% to 20% w/v of a first hydrophilic polymer diluted in an alcohol;
• and
• a second fixing buffer comprising:
• 5% to 30% v/v of a second hydrophilic polymer,
• 0.01% to 1% v/v of a detergent, and
• 0.005% to 1% w/v of a chrome alum, wherein the second hydrophilic polymer, detergent, and chrome alum are diluted in saline,
• wherein the first fixing buffer is applied to the cells at a temperature between −90° C. and −5° C.

A reagent system for fixing cells, the reagent system comprising:

• a first fixing buffer comprising:
• 5% w/v of a first hydrophilic polymer diluted in an alcohol;
• and
• a second fixing buffer comprising:
• 15% v/v of a second hydrophilic polymer,
• 0.4% v/v of a detergent, and
• 0.01% w/v of a chrome alum, wherein the second hydrophilic polymer, detergent, and chrome alum are diluted in saline,
• wherein the first fixing buffer is applied to the cells at a temperature colder than −15° C.

A method for fixing a cell, the method comprising:

• applying a first fixing buffer to the cell at a temperature colder than −5° C., the first fixing buffer comprising:
• 3% to 20% w/v of a first hydrophilic polymer diluted in an alcohol;
• and
• applying a second fixing buffer to the cell, the second fixing buffer comprising:
• 5% to 30% v/v of a second hydrophilic polymer,
• 0.01% to 1% v/v of a detergent, and
• 0.005% to 1% w/v of a chrome alum, wherein the second hydrophilic polymer, detergent, and chrome alum are diluted in saline.