A positive result is the development of an intense, dark blue or purple color directly over the biopsy specimen.

As you can see, the dark color can cover the entire biopsy or only part of the biopsy specimen. Even a small but readily visible area of dark purple or blue is a positive result.The positive control spot must be dark blue or purple for the test to be valid.

A negative result is confirmed only at the end of one hour (60 minutes). The positive control spot must always be dark blue or purple as shown. The visual representation in our Quick Reference Guide represents the typical appearance of the control spot at the end of 60 minutes. The spot will be smaller and more patchy when it first develops. The area immediately above the biopsy specimen will show no color change or infrequently may show a light blue or pale grey shadow (as shown here). The appearance of these shadows or footprint patterns is still considered a negative result.