Test Kits - How Accurate?

Saw this on FB. Interesting findings, although the control could've been a little better. The tests they did at the end are a little more conclusive. Looks like API isn't too bad after all on some things! :P Personally, I'm liking the Salifert Nitrate kit much more than the API though.

I remember reading a study of different (non-expired) kits tested against professional lab equipment. I based my decision to go with the seachem kit off of that study, since the results were the least variable, most consistent across multiple seachem test kits, and closest to the professional tests. The thing that bothers me about the above study is that so many of the kits used were expired that I think its really hard to interpret the results. I did find the salinity reading of the cheap e-bay chinese knock-off refractometer to be scarily astounding!
I wondered about that too, but it never said if they calibrated the refractometers before using them. If that refractometer hadnt been calibrated, it could very easily give a wrong reading, which is what I suspect because all the others read dead on.

And I think it good that they did the tests with expired kits, because that is probably what most of us are using.

I honestly dont test anything but alk and my salinity now, and I do double check my alk results against the store's results. If I have other issues, ill see it before a test kit can pick it up.
I just ordered a refractometer from Ebay. Not sure if it needs calibrated, but it includes the screwdriver to do so, so I'm thinking maybe it does. We will see, but it does come with a 3 year warranty from manufacturer and seller gives a 2 year warranty against defects so if I end up getting some crazy readings then I'll just return it. My hydrometer is reading between 24-25 so that will give me something to compare to.
you will need to calibrate it, but you need the calibration fluid to do so.

Its very easy to calibrate a refractometer, just place the drop of saltwater mixed to a specific salinity (usually 35 ppm) and then you use the screwdriver to move the parts so that the reading line is in the correct spot