Fluidic systems involving incubation of samples and/or reagents

A method, comprising:

• exposing a sample comprising vitamin D bound to a vitamin D binding protein to a release agent;
• releasing the vitamin D from the vitamin D binding protein;
• introducing the sample subjected to the exposing step into a fluidic device comprising at least one microfluidic channel;
• flowing, at a first flow rate, at least a portion of the sample into a microfluidic incubation channel;
• reducing the flow rate of the sample to a second flow rate after a leading edge of the sample enters the incubation channel but prior to the leading edge reaching an exit of the incubation channel, wherein the leading edge is a sample/gas interface, wherein the second flow rate is less than the first flow rate and/or is zero to allow incubation of the sample in the incubation channel, and wherein the incubation occurs for at least one minute at a temperature of at least 30° C.;
• modulating the flow rate of the sample to a third flow rate which is greater than the second flow rate;
• and
• determining an amount of vitamin D in the sample.