PSA testing comparison question

[LongevityAT]

I know that PSA results can vary, particularly if processed by different labs. Knowing this, I do have a question. Quick recap, I completed 20 rounds of radiation at UCLA with Kishan back in April of this year. At the same time, I began 6 months of ADT. Over the past few months, while getting my monthly Firmagon injections, my Urologist would do blood work. My blook was always drawn first thing in the morning and processed by the same lab. Each month that passed, my results were lower. Here are my PSA levels during the last 4 months of ADT (was mid 4's when I began radiation) -

June - 0.172

July - 0.089

Aug - 0.049

Sep - 0.032

For reasons I don't mind sharing but would take too long to describe, I fired my Urologist after my last Firmagon injection (they don't know this yet, I'm just not going back to them). So fast forward to this past week and I needed more blood work for PSA and T in preparation for my quarterly call with Dr Kishan in 2 days (Tuesday), so I went to my primary care doctors office for the blood work. To be honest, I didn't consider they use a different lab than the Urologist before having blood drawn last week. Regardless, the results were posted in my patient portal this weekend and my PSA jumped to 2.180 (from 0.032 just 5 weeks ago).

My question is, knowing that 2 different labs processed my blood, could different labs result in such a huge difference? I'm going to ask my Urologist office to take blood work tomorrow and see what number their lab comes up with but I know the results will not be ready before my call on Tuesday. I'll probably reschedule my call with Kishan to next week but would still appreciate any thoughts regarding the discrepancy in numbers I have experienced in just 5 weeks.

[Tall_Allen]

Did you end ADT? What is your T level?

[LongevityAT in reply to Tall_Allen]

Yes, received my last Firmagon injection on Sep 5. My T on that date was 12 but have not received the updated lab result from last weeks blood work for any change in my T. Still having some hot flashes so not sure there is much change yet. I received a total of 6 injections.

[Tall_Allen in reply to LongevityAT]

So your PSA is expected to increase when your T comes back.

[LongevityAT in reply to Tall_Allen]

Yeah, but the 30th day since my last injection was only 10 days ago, wouldn’t expect much, if any increase at this point. However, should be able to get the exact number tomorrow and will post it.

[Scout4answers]

Since they do not know you have fired them I would ask them to give you a psa and T test so that you have continuity and then compare to other tests.

[LongevityAT in reply to Scout4answers]

Thanks Scout, that’s exactly what I plan on doing!

[Justfor_]

No way to attribute such an enormous PSA variance to different labs. I have used 5-6 different labs for more than 50 tests in total and the max variance among them has been less than 40%. Lab errors are possible but another story. Your case is most probably what I call the sudden release of the compressed spring effect. It takes place when hormonal PSA suppression wears out.

[LongevityAT]

Got my T numbers from the blood work last week and on Oct 11 Testosterone was 17.3. So, starting to rise since ADT is complete (T was 12 on Sept 5). Will have more blood drawn today to have PSA number from same lab as prior tests.

[NotDFL]

Since your T is still low, it looks to me that there's a mistake with the latest PSA test.

We will find out soon enough.

[de-luke]

I am not a big fan of LabCorp. I get all my blood tests at my hospital , Mt Sinai, NYC Upper east side