All the tests that are PSA dependent -- PSA, Free PSA, PHI and 4Kscore -- are affected by prostatitis. None of them replace a biopsy. Their point is to show if it is safe to forgo a biopsy. None of them are very good, but PSA is the worst biomarker and % free PSA is a bit better. Neither of them have cutpoint where one can say with any confidence that a biopsy is highly likely to be positive or negative. PHI and 4Kscore, unlike those, have a cutpoint that simultaneously predicts the necessity of a biopsy reasonably well, or at least better than the other two. For example, if your PHI is over 35, your odds are 2/3 of a positive biopsy, and 1/3 negative due to a false positive. If your PHI is under 35, your odds are 2/3 that you can safely forgo a biopsy, but 1/3 that it will be unsafe to forgo a biopsy due to a false negative. See what I mean? Not great, but better than the others.
If your prostatitis goes into remission and your spike disappears, % free PSA will go up, PHI and 4Kscore will go down. There is a correlation between Gleason score and PHI or 4Kscore, but not % free PSA. The correlation is not strong enough to give it any grade-predictive value.
You are right to put "if" you are able to control the prostatitis in quotes. It is extremely hard to control. Antibiotics usually don't work and pathogens can rarely be identified. It is often relapsing and remitting for a lifetime. You just have to wait it out, treating the symptoms.
Allen - not an MD
•PSA=7.3, prostate volume=55cc, 8/17 cores G6 5-35% involvement
•SBRT 9 yr onc. results
•SBRT 7 yr QOL results
•treated 10/2010 at age 57 at UCLA,PSA now: 0.1,no lasting urinary, rectal or sexual SEsmy PC blog