Vacuum diagnostic device

A diagnostic device for testing at least one analyte in a liquid, the diagnostic device comprising:

• a housing having an exterior and including a chamber having one portion open to the exterior of the housing and another portion closed from the exterior of the housing;
• a porous structure disposed across the open portion of the chamber and hermetically sealed to the housing, the porous structure having a first surface communicating with the exterior of the housing, a second surface communicating with the closed portion of the chamber, and at least one layer which is wettable by a liquid;
• and
• means for increasing the volume of the closed portion of the chamber to thereby decrease the pressure within the closed portion of the chamber, the at least one wettable layer of the porous structure having a bubble point such that when the at least one wettable layer has been wetted by a liquid, the diagnostic device is capable of maintaining a pressure differential across the porous structure after the volume of the closed portion of the chamber has been increased by said volume increasing means to create a pressure differential across the porous structure.