The numbers quoted in the Q&A are for very low limits: See the quote attached at the bottom of my post. (All numbers are ng/ml)
They are looking at values less than 0.01 with a variation of .002.
As long as we understand that the machine variation is 20% for values less than 0.01 we shouldn't get heartburn if we see a number go from 0.010 to 0.012.
But using a machine with a useful detection limit of 0.1 (and presumably with the a 20% CV) IMO is not sufficient to detect a true rise until quite late in the game. Imagine you have a PSA drawn every 6 months and your true PSA begins to rise from 0.02 to 0.06 to 0.09 to 0.12. The single digit report would say "<0.1 " for all of them (2 years) at 0.14 and 0.16 the report would finally say " 0.1" . ( 3 years) At that point , your Uro might even say "Well that is the resolution of the machine so no worries. See you in another 6 months! Finally you hit 0.18 and maybe the report finally says 0.2. Do you trust that one or take another? You would have missed starting treatment early by 1 to 2 or even 3 years.
Back in 1995, 0.1 resolution was the norm. Equipment could not get down to lower levels at reasonable cost. Machines and detection limits have improved tremendously (30-100x) since then and so has our knowledge of early treatments.
The 0.1 resolution is fine if you have a prostate. But after RRP and other treatments, you need the extra digit.
Make sure the diagnostic box is checked and don't get excited if the variation is less than 0.02.
If you are going to demand have an accurate test and want consistent, comparable results, it is your obligation to be consistent too. Go to the same lab every time. Take the test at the same time of the day, eat or not eat in the morning but be consistent. Be consistent with your sexual activity, and medications.
In my case, I take the test in the morning, nothing to eat after midnight, no sexual activity for 2 days before. Does it make a difference? I really don't know - I have not done the experiment. But, I do know that I want that extra digit to count, so I do everything in my power to help. It is the burden I accept for insisting that the on "Diagnostic" box is checked on my lab request sheet.
Jeff (0.05 - and watching it like a hawk)
From the Q&A above:
"So-called 3rd generation PSA assays must have clinically useful detection limits <0.01 ng/ml. Analytical sensitivity needs to be < 0.005 ng/ml and functional sensitivity (20% cv) <0.01 ng/ml. An assay control with target concentration near this concentration is required and should be monitored each shift the analyzer is run. We observe between assay cvs of <10% over many months. Stable control materials are available from several manufacturers. It may also be useful to use aliquots of serum obtained after prostatectomy but gradual loss of immunoreactivity from deep frozen samples has been observed. We have not observed significant lot to lot variation in the estimate of these low concentrations but reagent lot changes, particularly of substrate, should be examined closely. The DPC Immulite assay is essentially equimolar in its detection of PSA isoforms. We observe differing baseline estimates of “PSA” in men post prostatectomy, varying from near 0.001 to near 0.01.
"The DPC Immulite sensitive assay, which has an analytical detection limit of about
0.002 ng/ml, functional sensitivity (20% cv) of about
0.005 ng/ml and clinically useful sensitivity of about
Married 34 years, DX Age 56
. First routine PSA test on April 8, 09: 17.8. Start 2 weeks of Cipro to rule out protatitis. May '09 PSA: 22.6, 3 weeks later: PSA: 23.2
. Biopsy 6/10/09
: 7/12 scores positive, 20%-70%, Gleason 6=3+3. Bone and C/T scans neg. RP DaVinci -7/21/2009
@ Univ of Roch Medical Center
Left nerve gone, right partial spared. Catheter removed - 7/31/2009
Pathology report received:
Gleason 3+4=7, Tumor size: 2.5 x 1.8 cm,
location: both lobes and apex.
Extraprostatic extension present; Perineural invasion: present, extensive.
No Malignancy in Seminal Vesicle, vasa deferentia, lymph nodes 0/13
Prostate mass 56 grams. Pathologic Stage: pT3aN0MX Post Surgery Status: Potency -
12/11 5 months, Still no activity, zip. Using pump daily since 11/11. No effect with 20 mg of Cialis or 100 mg of Viagra. Shots, See Uro 1/22/10 Trimix unsuccessful. Incontinence -
8/20 4 full pads per day
.. 9/7 3-4 full pads per day (Try cutting down on fluids. Bad idea. I know.)
11/14 4 months: Still 3 pads per day. 420ml/day, 91 um leak.
12/11 5 months: Still 3 pads per day. 400-450ml/day
1/11/10 6 months: Still 3 pads but leak is now 320 ml (5 day avg.)Post Surgery PSA -
9/3 6 weeks - 0.05; 10/13 3 months - 0.04, 1/14 6 months - 0.05.
Post Edited (Worried Guy) : 2/8/2010 5:54:15 AM (GMT-7)