This may not be exactly the same, but I have followed a similar idea which I got from the original Atkins book (1972). The book discussed testing for ketones while adding back carbs to see what kicks you out of ketosis. After identifying and removing the offending carb, the book recommends going back to induction to restore ketosis. It also says if you have a hard time getting a positive ketone test then switch to a true zero carb diet for a couple days to clear the carbs out of the liver. I had never seen the purple color on the test strips, usually getting a negative or trace at best result, even eating around 20g of carbs. I tried this, eating only meat, cheese and eggs for two days and then switching to the Atkins 72 level 1, which allows two salads or 1 cup each per day (less than 10g total carbs per day). I found that my blood glucose (non-diabetic) dropped dramatically after the 2 zero carb days and I saw purple on the test sticks after completing the 2 days less than 10g carbs. I am currently experimenting with maintenance, and have been in and out of ketosis several times and found this to be the fastest way for me to get back in ketosis.