In November I had a CA-125 blood test. It came back 21. The previous result was 14. I went for a retest in December and it came back 20. So it looks like it is now stable but at a different level. Keep in mind that my CA-125 was 17 when I recurred on my liver and spleen in 2008 so of course there is concern that my number was trending up - even in the normal range.
I decided to look more closely at the test results sheet because the results were reported as normal < 35 and I had thought the normal for the tests I had been having was < 21.
Here is what I found on the sheet:
" THIS TEST WAS PERFORMED USING THE BECKMAN COULTER CHEMILUMINESCENT METHOD. VALUES OBTAINED FROM DIFFERENT ASSAY METHODS CANNOT BE USED INTERCHANGEABLY. CA125 LEVELS, REGARDLESS OF VALUE, SHOULD NOT BE INTERPRETED AS ABSOLUTE EVIDENCE OF THE PRESENCE OR ABSENCE OF DISEASE.
So I went back to the report from August 2014 and sure enough the normal for the test was reported < 21.
The report said:
" THIS TEST WAS PERFORMED USING THE SIEMENS (DPC) CHEMILUMINESCENT METHOD. VALUES OBTAINED FROM DIFFERENT ASSAY METHODS CANNOT BE USED INTERCHANGEABLY. CA 125 LEVELS, REGARDLESS OF VALUE, SHOULD NOT BE INTERPRETED AS ABSOLUTE EVIDENCE OF THE PRESENCE OR ABSENCE OF DISEASE."
Ugh! "Look they went and changed the method!" Maybe that is why my CA-125 went up. The last time the method was changed the lab followed it using both tests for a few months to see how the results correlated. I was in treatment then and we were following it closely to make sure the chemo was working.
Being the research "hound" that I am I got on Google and investigated how the tests are done and what the difference was between the two methods.
I learned that both tests - are chemiluminescent immunoassay tests. They use a monoclonal anti-CA125 antigen alkaline phosphatase conjugate and paramagnetic particles which are then separated in a magnetic field. A chemiluminescent substrate is added and the light generated by the reaction is measured with a luminometer. The light produced is proportional to the concentration of CA-125 antigen.
From what I read the Beckman test uses two mouse monoclonal antibodies while the Siemen uses one mouse antibody and one rabbit monoclonal antibody. I am going to assume that is was causes the difference in results since all the tests were being done by the same lab.
The up and down of CA-125 results causes enough anxiety without having a different method which could be the cause of the change thrown into the mix.
I probably should have looked more closely at the results when they first came in before getting nervous.
I will be seeing my gyn onc in February and had a CT scan today so I think I will have my answer if it is something I should really worry about.
Every Day is a Blessing!