Easy@Home Marijuana Drug Test Kit for Urine - THC Tests for Home Use (10 Pack), Weed Detox Testing Kits with 50 ng/ml Cutoff Level, #EDTH-114

I was a forensic toxicologist for 20 years and have had friends and coworker ask me about testing for THC over the past few years since it has been legalized in many states for recreational use (including my state). I handled R&D for SAMHSA/NIDA confirmatory testing by GC/MS, as well as initial screening by immunoassay using various instruments (Hitachi, Olympus, etc). Since these were FDA approved and to SAMHSA standards, they would more than likely perform as expected.In order to recommend quick test strip kits to people, I decided to try some kits. This product performed well in my testing. I used myself as a negative control and the expiration of the strips I received were in 2019. The result was correct with the THC patient line being the same density/color as the control.I then tested a known user at two stages. They were a light user so I tested 1 hour after use and the test was as expected, with a slight positive (faint line on the THC but less prominent than the control). At 1 hour I expected it to be either negative or slightly positive due to the cannabis metabolism rate (but it can vary depending on the individual). I also tested after about 8 hours and it was positive with no THC line and the control line was valid.I have read reviews that say their test did not match the result when sent in to a drug lab and I would warn people that this can be due to many factors and most do not relate to the strips. The ones which could be strip related are expiration, faulty storage, faulty manufacturing (it can happen with any lab test, including reagent based).The most likely cause, however, is that this is a urine test. Urine tests are notorious for being dependent on the concentration of the urine. If you test on a dilute urine and it is negative but then test on a more concentrated urine and it is positive, this is not an invalid result. The same goes for a concentrated urine coming up positive and another test being more dilute coming up negative. If you want to match test results, you would need to do blood tests or check specific gravity or creatinine levels for a THC/Creat ratio.Also you are comparing two different tests. One is based on a test strip and the other is based on an analyzer that used reagents and much better immunoassay techniques. With a strip (as in thin layer chromatography), the result is dependent on the person performing the test being able to distinguish colors and bands, variations in intensity/density, etc. These are also qualitative assays and a 50ng/mL cutoff will vary greatly above that limit. You may not be able to detect even over 100ng/mL by eyesight. Analyzers in a lab use photometers for detection.From what I have seen, I would place these up with any other well made test strip. I would just be sure to return any you get that are close to expiration, which will greatly deteriorate results and more than likely make them invalid. These would be of most use for testing kids or others where you want to know if they have been using cannabis as long as you know to use a concentrated urine (first void after waking works well). I would not use them during a period of fluid intake because that would defeat the purpose. You could also use this to get a ballpark figure of THC levels by serial diluting the urine and testing each dilution to see when it comes up negative. There is no way to know the actual level but if it takes many dilutions (like 1:20) you can be sure the level is fairly high and will take much longer to clear, even on a concentrated sample.