What is the Phadebas test?

The Phadebas test is a commonly used forensic screening method for the possible presence of saliva.

It works by detecting the enzyme alpha-amylase, which is found in high concentrations in saliva. When the enzyme is present, the test produces a colour change indicating amylase activity consistent with saliva.

The test is commercially available and may be used in different formats. It can be applied as a press test to help map the location of possible saliva on items such as clothing, or as a tube test applied directly to swabs or extracts collected during examination.

However, the test does not identify saliva itself. It detects a biological marker commonly associated with saliva, but not exclusive to it.

Alpha-amylase can also be present in other forensically significant biological materials, including vaginal secretions, faeces, and urine. A positive Phadebas result therefore indicates that amylase activity was detected, not that saliva was definitively deposited.

The test is typically used as an initial screening step. Further testing and interpretation are required to assess what the finding may mean in context.