Bioequivalence and Bioavailability Forum

Hi ElMaestro,

❝ Now, how (or rather why) the [expletive] does one report concentrations with 5 significant digits from std curves produced from such standards?

Measured with a method for which the tolerance limits for precision and accuracy are 15% (20% at the LLOQ)...

(Well, actually I've seen worse than 5: sometimes 6 or even 7. And only very occasionally people using a fixed number of significant digits rather than a fixed number of decimals).

❝ Does anyone, anywhere have anything better than "those are the rules" and "we just follow the standards"?

"I left my brain in a jar at the door" ? "That's what the FDA requires" ?
The basic rule I was taught in my 1^st year at University: you can't give a result with more significant digits than the lowest you have in any of the figures you use to calculate it. Use full precision for calculations, but always round to the lowest number of significant figures to give the end result. We actually lost points if we gave too many significant figures at an exam.
This being said, if you give a result with only 2 significant digits and your LLOQ is 10 pg/ml, you would get a first step of 10% between 10 and 11 pg/ml, which is not great regarding precision and accuracy. I would not blame the use of 3 digits in such circumstances.