For the simplified use of a test strip holder, a device having a holding or positioning device is provided, comprising a mixing chamber, a lid for closing the mixing chamber, and an obvious fluid opening for a fluid passage from the mixing chamber to the test strip holder. This allows for the test strip holder to be inserted into the device in a simple way and a sample can be prepared in the mixing chamber of the device. The device is provided with a mixing chamber that can be closed, wherein a reaction partner, for example a gold conjugate, can be dissolved in the sample for increasing the sensitivity of the test strip.