A device with a vessel for saliva that has one or more optical indicators to show the volume of saliva in the container. The optical indicators use the principle of total internal reflection together with the difference in refractive index between saliva and air. In embodiments, suitable visual indicators are either visible or invisible, when reflecting surfaces are either not immersed or immersed in saliva or vice versa. The device may comprise a vessel with a saliva pathway, a saliva containment region defining a saliva reservoir, the reservoir having a desired fill level, and an optical viewing window adjacent an angled reflective surface for level indication and/or validating a fill level. The device may include patient interface components and chemical test strips.
