The LeanScreen technology, is very accurate and explained how it works here: https://postureco.desk.com/customer/portal/articles/1622598-how-does-leanscreen-actually-work-
This method is very accurate when performed correctly. However, we have had many requests, particularly with personal trainers to include an additional way to incorporate their existing and current methods of Body Composition Analysis, (for example an InBody, BIA, or calipers). Using the PostureScreen version of LeanScreen, this is currently available starting in version 5.0.
Once enabled you can enter body composition type and what the percentage was, and the new results with LeanScreen will refelect an average of the two methods, bringing an unparalleled level of accuracy.
This addition will also be incorporated in future version of the standalone LeanScreen application.
Here is a video explanation on how this works: http://youtu.be/tYjJTDxp7Ts