PSA test at different labs

[Mgtd]

In reading posts about PSA testing I consistently read that they should be done at the same lab.

My question is how critical is that advice. What is the normal difference in PSA between different labs?

Thanks.

[MJCA]

I use one lab for my PCP and another for my oncology team. There are some differences; my PSA is on the rise. One lab was 296.0; the other 303.0. So the differences between lab one (Quest) and lab 2 (Stanford University Medical School) are not great.

[Mgtd in reply to MJCA]

Thanks. I kinda suspected that within the USA there would not be that great a difference percentage wise. In fact it will be even less of a critical difference at lower levels of PSA. At this point in my disease it may be do be deal.

The reason I was asking is that in the hospital lab I am in and out in 15 minutes where the Sonora Quest takes upwards of a hour or more.

[Justfor_]

If you are after the PSA trend, same lab is better. If you want to establish a value to gauge your state against recommendations, studies, etc, an average of many labs is preferable. There was a round-up test in Germany where the same blood samples were sent to four hospital labs that used four different analyzer - assay kits. Each individual count was compared against the average of all four. Highest was Roche, followed by Abbot Aliniti, Siemens and Beckman Coulter the lowest. An approx. 15% spread was observed between the highest and lowest.

[Mgtd in reply to Justfor_]

Thanks

[Tall_Allen]

Can be a 20% difference, depending on the test.

[Mgtd in reply to Tall_Allen]

Thanks. That upper limit of 20% gives me something to work with.

My MO draws blood work in-house. I am not sure who or where the actual blood is processed. My GP and RO send me to Quest. So I am between a rock and a hard place.

When I went to my hospital lab and the local Quest lab they were all in the ballpark. I assume there is no way to really pinpoint the accuracy from place to place or even operator to operator.

I prefer the hospital lab since I am in and out in 15 minutes. With Quest I can be a hour or more depending on the number of people waiting. Appointments are rather limited.

[NanoMRI]

If lab results are significantly different how do you know which one is correct? Certainly we can all agree laboratory testing is far more accurate than political polling.

I have been puzzled by need/purpose on this question of different labs since I began screening in 2008, as I use labs in different US States and several European countries. In the last ten years I have had upwards of 75 tests in different labs and I have no concerns for 'error'.

As I had RP I rely on <0.010 as best indicator and values above as concerning. Whether one uses <0.010, 0.1, or 0.2, even differences as large as 20% are not significant if one understands it is a continuing rising trend above your chosen value for 'recurrence' that matters.

I believe this "same lab' narrative is driven by factors other than accuracy. 'In-house' labs provide financial benefits and perhaps more importantly control over what value to report to the patient. When I bring my lab results to a doctor they have to manually input the information - this method is unwanted added work for an already overwhelmed business. I self-direct my testing and this provides me with control - not all doctors are comfortable with this.

[Mgtd in reply to NanoMRI]

The basic reason I asked the question was out of curiosity and having a reference as to how significant is it evaluating results from different labs.

It seems one or two of the questions/statements that seems to always come up are on the forum are:

1. Are your PSA tests from the same lab?

2. Evaluating high sensitivity with “normal” PSA test results because they use a totally different methodology.

Some of the other statements that seem to pop up from time to time are things like time day, exercise, sex, riding a bike, etc. These can be quickly researched on Dr Google but the impact of lab differences in my experience has not been so straightforward.

[NanoMRI in reply to Mgtd]

have you experienced lab differences that are unresolved?

[j-o-h-n]

Always go to the lab with the prettiest technicians.

Good Luck, Good Health and Good Humor.

j-o-h-n

[Mgtd in reply to j-o-h-n]

Yep and the one with sharpest points on the needles.

[j-o-h-n in reply to Mgtd]

Dull needles are reserved for ex-wives..........

Good Luck, Good Health and Good Humor.

j-o-h-n

[Cyclingrealtor]

PSA is only a biomarker. It shows changes and abnormalities in the prostate.

After an RP, rises in psa become more concerning and should be followed with imaging and/or a blood biopsy to have a better understanding of what the psa number is indicating.

The challenge is, what do we do with a psa result?

If you're screening it's about ruling out what's driving the PSA - benign issue or cancer?

The debate around the variance of up to 20% is really irrelevant, IMO, because there's no way to quantitify how much more cancer is or isn't there.

Another important factor is making sure the same make and model are being used. So typically using the same lab helps keep testing on the same equipment in check.

So a 20% difference between a psa of 7.0 and 8.4 means what?

While a single increase may raise an eyebrow, one rise doesn't constitute a trend and more psa testing should be considered.

[Mgtd in reply to Cyclingrealtor]

Thanks for the input.

[Mgtd]

No just thinking ahead because I will be most probably be using up to three different labs over the next couple of months or so. My plan was to use different ones over the upcoming months and see if I find any real differences between them. MO, RO and GP have all ordered blood work in a relatively short time period.

Currently my PSA is starting to show a small rise of 0.02 to 0.03. Nothing critical at this point.

I will let you know how my experiment turns out.