Halbert, are you saying that if Labcorp can detect down to 0.006 and your test happens to result 25.000, they should report it to you as 25, but if they measure 25.001 they should report it as 25.001?
"So, it appears that the Abbot test defines and requires the use of ONE significant figure. Hence, the use of 0.1, not 0.10."
Why would Abbott report a result as 0.1 if they their lower limit is actually 0.10? (Just as they would report the next higher results as 0.11 and 0.12.) Are you saying that Abbott detects to only one decimal?
Mumbo wrote "My GP, URO, and I believe RO (not affiliated in any manner and none use the same lab) seem to all use an Abbott Assay that provides PSA results to two digits
to the right of the decimal point with the lower limit at <0.10."
Aren't there two separate issues: the number of decimal places reported, and the value of the right-most digit at the lower limit of detection? For Quest that value is a 2 (0.2), for Labcorp a 6 (0.006). Why can't it be a 0 for Abbott (0.10), with anything lower reported as <0.10?
"Trailing zeros in a number containing a decimal point are significant.
For example, 12.2300
has six significant figures: 1, 2, 2, 3, 0, and 0. The number 0.000122300
still has only six significant figures (the zeros before the 1 are not significant). In addition, 120.00 has five significant figures since it has three trailing zeros. "
(First thing I happened to find online
, emphasis mine.)
So 0.1 has one significant figure, 0.10 has two, which for me explains why Abbott uses <0.10 as it's undetectable.
(Let's set aside standard deviation, but I think you need +/- 2 S.D. to include 98% of values. An independent lab looking at report to the thousandth place in lab assays, happened to choose this ROCHE PSA assay as their subject, and found 1 S.D. was 0.001 for a target PSA sample of exactly 0.01, a bit higher for a target of 0.1. So it's a pretty good assay.)
Post Edited (DjinTonic) : 7/21/2021 3:26:05 PM (GMT-6)