Different test different results

[drvrcrzy]

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. What gives? Should I ignore the tests with the very faint line or take it as a sign that these tests are finding traces of THC at the 50ng level and that I should back off the intake? I know that none of this testing is an exact science but I'd like some feedback to others experience with this situation.
Thanks!

drvrcrzy Reviewed by drvrcrzy on 01-25-2014. 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

[Burnt Toast]

Contrary to popular belief, line intensity is not proportionate to THCA levels in the urine. If it were, then completely drug-free specimens like synthetic urine controls (as well as your tap water tests) wouldnt be producing faint lines on an assay.

A faint line is still a negative. A negative is a negative.

[drvrcrzy]

Thanks, but what do you make of two separate manufacturers strips with opposite results? One with two solid lines and the other with only one line. Both tests done at the same time using the same sample. And on one strip you almost need to use your imagination or hold it at certain angles to see it? Are the comments I've read that say " a very faint line demonstrates thc levels at or near the cutoff? Is this totally bogus?. If I was the lab I would question such a faint line and find it hard not to find it positive when it is so hard to see. I get the feeling that I have one set of strip tests that don't have sufficient color on the test line. Your thoughts?

[drvrcrzy]

Also, are these dip strip test considered "EMIT" tests? I tried 4 aspirin 3 hours prior to test with no difference to either brands test strip.

[Burnt Toast]

Thanks, but what do you make of two separate manufacturers strips with opposite results? One with two solid lines and the other with only one line. Both tests done at the same time using the same sample. And on one strip you almost need to use your imagination or hold it at certain angles to see it?

Too bad that you didnt post any pics of these tests. That wouldve been a big help in answering this.

Rule of thumb - if it can be photocopied, its a line.

Are the comments I've read that say " a very faint line demonstrates thc levels at or near the cutoff? Is this totally bogus?.

Yep. Because to conclude this as such would be sheer speculation, as assays lack the ability to yield a quantitative value (unlike the GC/MS).
And again, if this was actually true, then like Ive pointed out before, synthetic urine controls and your tap water tests (again both specimens containing zero drug metabolites) wouldnt be producing faint lines on an assay.

If I was the lab I would question such a faint line and find it hard not to find it positive when it is so hard to see.

Even if an untrained tech were to misinterpret a faint line as a "non-negative" and sent the sample off for the confirmation GC/MS, the sample would come back as a negative.

Also, are these dip strip test considered "EMIT" tests?

The dip tests function on the same principle as the EMIT, as they utilize enzyme-based reagents for the analyzing process.

[drvrcrzy]

Thanks all. But to clarify. The known negative samples such as the tap water were performed on two different dip strips made by two different companies. The one I trust has a solid test line. The test I'm skeptical about has an extremely faint line even with tap water. That's why I keep questioning my own test. I test clean on both tests one day. The next day after one hit the trusted test still has a solid test line and the test I'm skeptical of has no test line or so damn faint that I can trust my own vision to whether its really there or if I'm imagining it. IT's THAT light after one hit. I thing I have a crappy set of strips! I'll run another set of test in a day or so and see if I can post the pics.

[SlinkyDinky]

Why are you even testing yourself after taking one or two puffs? You're FOR SURE going to test positive, so it's a pretty redundant endeavor.

Do both brands have the same cut off value ? Are you sure of the expiry date of both ? Lightness of the line HAS NO RELATION TO ANYTHING. Faint line, thick line, kinda-thick line, kinda-not-so-thick line, kinda-faint line...whatever, it all means the exact same thing.

[drvrcrzy]

OK. Check these Pics. Both tests done at same time in same actual urine sample. Like I said - if you use your imagination you can barely see a faint line on the left strip. And of course a nice solid line on the right strip ( assuming my photo attached properly ).
Ask yourself which one you would trust if you were to be tested in one hour.
Testing plain tap water yields only a slightly darker line on the left strip which is why I tend not to trust that left strip.
Which one would YOU bet your job on?Attachment 297991
I think I'm asking questions with no answers, but I'd love to hear what y'all think.
Thanks.

[drvrcrzy]

Please see the pics I just posted. I might have posted out of place. Both brands cut off at 50ng. Expiry date on both is into 2015. Check the vast difference.
And why would I FOR SURE test positive after only one or two puffs?? How could so little possibly raise my thc to detectible levels? And you can see that the strip on the right is clearly negative after two hits plus residual from one week ago. I've done test in the past taking two hits at a time until the test showed non-negative and it took almost 10 hits to start losing that line. Please explain - just trying to learn this tricky game. Thanks

[drvrcrzy]

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?