Saliva testing is a newer, less proven technology. The sensitivity of saliva tests is not well established in the case of marijuana. In theory, they are supposed to detect recent use, but this may range from several hours to over a day. They are supposed to detect secretions from inside the oral tissues that cannot be washed out with mouthwash. Because they are less intrusive than blood or urine tests, the industry has been eager to develop saliva tests. Due to reliability problems, they have yet to gain acceptance in the ., but they have come into use in some other countries, such as Australia.
The PSA value used most frequently as the highest normal level is 4 ng/mL (nanograms per milliliter). However, since the prostate gland generally increases in size and produces more PSA with increasing age, it is normal to have lower levels in young men and higher levels in older men. Age-specific PSA levels are as follows (age group, upper normal): (40 – 49, ), (50 – 59, ), (60 – 69, ), (70 – 79, ). The use of age-specific PSA ranges for the detection of prostate cancer is controversial. Not all studies have agreed that this is better than simply using a level of 4 ng/mL as the highest normal value.