Pretreatment method of biological sample, detection method of RNA, and pretreatment kit

A method of detecting RNA in a sample collected from a living body, the sample containing lactoferrin, the method comprising:

• applying an inhibition treatment of RNA degradation activity due to lactoferrin to the sample collected from the living body;
• applying an inhibition treatment of reverse transcription inhibitory activity due to lysozyme C to the sample collected from the living body;
• and
• an RNA detection step of detecting RNA in the treated sample,
• wherein the inhibition treatment of RNA degradation activity due to lactoferrin is applied to the sample collected from the living body by adding an inhibitor of RNA degradation activity due to lactoferrin to the sample collected from the living body,
• wherein the inhibitor is at least one selected from the group consisting of copper, nickel, iron, gold, scandium, yttrium, gadolinium, cerium, neodymium, and zinc,
• wherein the inhibition treatment of reverse transcription inhibitory activity due to lysozyme C is applied to the sample collected from the living body by adding an inhibitor of reverse transcription inhibitory activity due to lysozyme C to the sample collected from the living body, and
• wherein at least one of the RNA degradation activity inhibitor and the inhibitor of reverse transcription inhibitory activity contains an iron ion agent and a carbonate ion agent.