Was there a Limit of Detection (LOD)?

One LOD was established to determine how small of a concentration of straight EDTA the test is practically capable of finding in a clean sample- that was 13 ug/mL (13 PPM). The tube maker's website states the tube sample would have 1800mg/L of EDTA in it. The test could detect amounts less than 1% of what would've originally been in blood from the vial.

They also tested blood in various sizes dried onto solid surfaces, swabbed up, and put through their protocol to determine the smallest detectable size of blood spot they could reliably find EDTA from. They tested 1 uL, 2uL, and 5uL samples. EDTA was readily detected in the 1uL and 5uL samples. It was indicated in the 2uL sample, but based on a problem with the ion levels, the analyst marked it as "not detected." An LOD is set at a level where you can detect your substance reliably 50% of the time you know it's present. That means at levels just above and below you may or may not detect all of the time, but the further away you get, the more reliable the test becomes. It's not a surprise the 2uL sample didn't work perfectly, as it was so close to the LOD. By the time they got up to 5uL, they were 100% accurate in detecting EDTA in known positive samples.

To give an idea of the sizes being used: 1uL of blood would create a drop about 1/50 the size of a penny.