Interesting Q&A on ultrasensitive testing

Although the discussion dates from 2003 it is still quite valid.

http://www.aacc.org/events/expert_access/2003/prostate/Pages/qanda.aspx

Bill

Interestingly, Dr. Menon's team advises AGAINST using the super-sensitive PSA tests. They cause to much grief.

I know Dr. Strum advocates using it.

Dr. Menon's team does NOT advocate that I have adjuvant radiation. Dr. Epstein at Hopkins does indicate that it should be strongly considered.

Obviously, there are plenty of grey areas in this disease.

Mel

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 0.01 ng/ml."

Good:

Maybe assault with a non-deadly weapon?

Mel

I think that one ng/mL works out to roughly one gram per swimming pool...seriously.

A US dollar bill weighs one gram.

Post Edited (Casey59) : 2/8/2010 7:21:09 PM (GMT-7)

Thanks for that additional analysis, Jeff.  Science rocks!!  As nerdy as it sounds, I think this stuff is pretty interesting.

Anyhow, you've piqued my curiosity regarding your comment "So, in 2010 it not unreasonable to expect PSA accuracies to 0.001 ng/ml. Whether it is worth the cost is a different matter."

My insurance pays about $175 for the standard PSA test (lower detection limit of 0.1 ng/mL).

This question is for you guys who have had the ultra-sensitive PSA test:  What is the cost of one ultra-sensitive PSA test?

regards

I have clearance...and have the scars to show it

My wonderful wife called the University of Rochester Medical Center lab and asked for the charges.

$85 for a screening PSA (1 decimal) and
$111 for a diagnostic PSA (2 decimals)

Plus $11 for the drawing the blood.

One caveat: The person my wife spoke to said the $111 was for screening and $85 for diagnostic. Diagnostic was cheaper! That did not make sense to me, maybe she read it wrong, so I reversed the numbers above. Either way, they are very close.

I made my contribution for today. Can someone else check their favorite lab?

Jeff

Carlos:

Does QUEST lab do the ultrasensitive test?

Mel

Carlos,
Thanks for the numbers. It seems that there is quite bit of variation between locations. Let us know when you get prices for the Post Protatectomy PSA. Given that the standard PSA is $ 35, I'd be surprised if it is more than $70.

Casey,
What a great find! That is the kind of data I like to see. Does this mean that anyone can walk in off the street and get a PSA test done without a doc ordering it? It does gall me to have to go to the Uro's office to get the darn number. I know what the numbers mean. Ok maybe the first or second time but after that, you are a big boy. You can figure it out. Why do you have to make an appointment, go to the office , pay a copay, to have the PA say: "Your PSA is 0.xx. See you in three months. Oh, Bend over... Nope, no prostate in here." ?

Hey Europeans and Aussies !
What are costs for single decimal and two decimal PSA tests in your neck of the woods?

Jeff

Post Edited (Worried Guy) : 2/9/2010 1:05:39 PM (GMT-7)

David:

All together now:  QUACK QUACK AFLAC; QUACK QUACK AFLAC!

JEFF: Do you have to make an appointment each time to get your PSA results? That's ridiculous. I just call and they tell me. I can even drop by the office and get a hard copy of any test results, free. Heck, they charge enough for my regular office calls!

Mel

An interesting comment for us "low risk" guys:

"Of particular significance, however, is the ability sensitive PSA measurements have to identify patients who are certainly not destined to have recurrent cancer. Such men are identified by PSA <0.01 ng/ml and no or minimal increases during the 2 years post prostatectomy."

 

The "0.01" is referring to the value after surgery, with the necessary waiting time for PSA decay. I have posted on this before, and I am curious as to why the LOWEST level for post-prostatectomy PSA is always the one after surgery. Of course, some guys unfortunately get a recurrence and their PSA trends up. For the guys that do not experience a clinical recurrence, their PSA trend can either be a) constant and low, b) fluctuating but low, c) minor increase, but stable below 0.1 or possibly 0.2. What I have NEVER seen is a trend DOWN from the PSA level after surgery. What makes the post-surgery level apparently the absolute lowest level that a man can expect during recovery?

 

CaPCa

I think MichGuy is a counterexample to your theory

Mel