Plus if this untrained tech WAS to misinterpret a faint line as a non-negative and sent the sample for GC/MS confirmation, wouldn't the GC/MS quantitative analysis show some detection even if below the 50ng level since they are testing below that level?
The cutoff threshold for the GC/MS is typically 15 ng/ml. But dont let this create another worry for you. Read this thread:
http://boards.cannabis.com/drug-test...d-testing.html

If the sample registers below 15 ng on the GC/MS, its ruled a negative - no quantitative value is provided because its not necessary - a negative is a negative. Above 15 ng is a positive and at that point a quantitative value is provided.
Burnt Toast Reviewed by Burnt Toast on . Different test different results I have used several brands of THC strip tests. On one recent batch the second line is very faint even when testing a known negative and even tap water while another brand test used at the same time has a nice bold line. The test with the very faint line seems to be very sensitive to even the slightest amount of THC. After getting repeated negative results, then taking as little as one or tow puffs - the line becomes almost invisible. At the same time the other brand shows a clear second line. Rating: 5