Q71) A 65 y/o African American man is brought by his daughter to you and requests a PSA test because there is a hx of prostate ca in their family. You perform PSA and DRE. DRE does not reveal any palpable mass. The lab test reveal : PSA : 9ng/ml, Free PSA: 0.5ng/ml. You reveal the results to patient and his daughter. The daughter asks you if her father has a cancer. Your best response is :
A) The PSA level increases with age and your father’s PSA is in the age-appropriate range
B) PSA level is very nonspecific and your father does not have a cancer
C) The fact that the free PSA is only 0.5ng/ml as opposed to a bound of 8.5 indicates that your father has a 50% probability of finding a prostate cancer on needle biopsy
D) PSA will not help in diagnosing carcinoma prostate
E) I did this test only because you requested for it, I do not think this results mean anything.
Archer USMLE Step 3 Blog 
c
c
C
The risk of cancer increases if the free to total ratio is less than 25%
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are you guys kidding ? you can ‘t diagnose the p.cancer only by PSA, further evaluation (biopsy) should be taken ,the answer should be D
Although I dont understand where the bound 6.5ng/ml comes from, C is the most likely answer. The reason is the Free PSA to total PSA ratio. The lower the ratio is (ie, the higher the total PSA level and the lower the free PSA level), the higher the lkelihood of having prostate cancer. In his case, the ratio is around 18% (usual cutoff is 25%) and for a patient aged 65 this means about 34% risk of having prostate cancer.
8.0 total-(1.5 free) yields 6.5 bound
PSA will not help in diagnosis of cancer. This is a controversial statement but the outcome of free or total PSA estimation will never mean cancer. Only biopsy will help in diagnosis.
Free PSA is just used to reduce the number of biopsies.
My answer is D
Dr. Red, could you share the answer please?
Only 30% of patients with high PSA have prostate cancer diagnosed after biopsy. (2013)”Current status of biomarkers for prostate cancer”
Today The only test that can fully confirm the diagnosis of prostate cancer is a biopsy– it is unethical and non professional to give a non proven Dx of Cancer to a Patient — this Dx is a life changer to the patient and not for good
American Cancer Society— Men with a PSA level between 4 and 10 have about a 1 in 4 (25%) chance of having prostate cancer. If the PSA is more than 10, the chance of having prostate cancer is over 50%.– this Pt has 25 % chance of having Prostatic cancer
free PSA test is a road sign to help determine whether further work-up and follow-up is necessary. NOT to miss inform and scare Patients —
Free:total PSA ratio test is particularly helpful in situations where a biopsy is negative but the PSA is slightly high. If there is a low free PSA, another biopsy 6-12 months later is usually recommended. Pt with a lower percentage of free PSA have a higher risk for prostate cancer –this patient Free:total PSA ratio is low — 0.18 risk for his age 65yo is aprox –.33.9% of risk of having prostate cancer —and NEEDS BIOPSY –no need to get to conclusions –Question Dr Red how many patients do you see a day and how often do you speak with them?
lol! rodo! cool down! lol, This is belligerent! I know. I am with you man. I can understand.
8 ng/mL is in the grey area. One can not say that this patient has prostate cancer or that this patient is cancer free.
1.5 ng/mL to 8 ng/mL is a free to total PSA ratio = 18.75%.
After adjustment for age, this patient has a 33% chance of a diagnosis of prostate cancer if a needle biopsy is done (Mayo 2015).
PSA is a probability or screening test for prostate cancer. It is a test to determine who should have a biopsy, who should be on the watch-list and who does not need a biopsy. It is interpreted in terms of positive predictive value. A total PSA of 4-10 ng/mL means one in four chance of finding prostate cancer if a needle biopsy is done.
PSA is not a diagnostic test. It is a test to decide who should have a prostate biopsy. The free to total PSA ratio is an attempt to lower the number of prostate biopsies. Only a prostate biopsy is diagnostic.
Here is a filter for this question. Any answer that says that this patient has or hasn’t got cancer is incorrect. Between 4 ng/mL and 10 ng/mL, this is indecisive at best until a biopsy is done.
Notice that Option A, B & C are out.
Any option that undermines the significance of the test is incorrect. This test gives the probability of getting a positive needle biopsy. A free to total PSA ratio below 10% or 0.10 means that if a needle biopsy is done, there is more than a 50% chance that it will be positive for prostate cancer. The index patient has a 33% chance of a positive needle biopsy for prostate cancer. Option E is incorrect
In conclusion, in this patient, PSA is not diagnostic for carcinoma of the prostate (Option D). So if the patient asks whether this is carcinoma of the prostate, one should say (to this patient) that PSA is not diagnostic of prostate carcinoma – “PSA will not help in diagnosing carcinoma of prostate” (this statement is tailored to this index patient).
Option D is the best reply to this patient.
Readings and references:
Total and Free PSA – Mayo 2015 http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81944
Prostate Cancer Screening: the continuing controversy – AAFP 2008 http://www.aafp.org/afp/2008/1215/p1377.html
Screening for Prostate Cancer – Uptodate 2015 – http://www.uptodate.com/contents/screening-for-prostate-cancer
after DRE psa levels invariably raise
Good job Rodo and Adnan. The statement “PSA will not help in diagnosing prostate cancer” is not correct either since it does aid in the approach . Also, a very high PSA level > 100 can be very specific of the diagnosis (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3285713/) . It would be correct if the statement said “PSA “alone” is not “diagnostic” of prostate cancer” because it needs further testing to confirm. But it is not correct to say “PSA is “not helpful” in diagnosing”. The word helpful just means it assists. Screening with PSA can help in detecting prostate cancer earlier in high risk populations. The underlying intention of this question is to test the value of Free/Total ratio in guiding who needs a definitive biopsy in those with borderline PSA elevations between 4 and 10. Having said that, the earlier version of choice C used the word “most likely has” which may sound more arrogant on the part of the doctor – instead it has been modified to give the most likely probability based on the free/total ratio. Discussing the probability ( likelihood) of an etiology does not equate drawing conclusions. It is always good to discuss the “probability/ likelihood” especially since patients do get worried when certain tumor markers are increased. You guys are doing a great job in analyzing the concepts…keep it up!
Good job Rodo and Adnan. The statement “PSA will not help in diagnosing prostate cancer” is not correct either since it does aid in the approach . Also, a very high PSA level > 100 can be very specific of the diagnosis (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3285713/) . It would be correct if the statement said “PSA “alone” is not “diagnostic” of prostate cancer” because it needs further testing to confirm. But it is not correct to say “PSA is “not helpful” in diagnosing”. The word helpful just means it assists. Screening with PSA can help in detecting prostate cancer earlier in high risk populations. The underlying intention of this question is to test the value of Free/Total ratio in guiding who needs a definitive biopsy in those with borderline PSA elevations between 4 and 10. Having said that, the earlier version of choice C used the word “most likely has” which may sound more arrogant on the part of the doctor – instead it has been modified to give the most likely probability based on the free/total ratio. Discussing the probability ( likelihood) of an etiology does not equate drawing conclusions. It is always good to discuss the “probability/ likelihood” especially since patients do get worried when certain tumor markers are increased. You guys are doing a great job in analyzing the concepts…keep it up!
Answer C
Thank you Dr. Archer for providing the refreshing explanation! May i ask why you didn’t provide an answer to this question? Or maybe you did within explanation but I am not aware of. LOL.
Thank you Adnan for ALWAYS providing the BEST and most easy to understand explanations/teachings with supporting evidence and reading. I really enjoy reading your explanations and Dr. Archer.
Question-
1. Yora- how did you come up with the ” bound 6.5 ng/ml?
And how did you come up with the Free PSA:Total PSA ratio being “around 18%”?
I am assuming 9/.5 = 18? But this is the total PSA:free PSA ratio.
2. Emorydoc- how did you come up with
“8.0 total-(1.5 free) yields 6.5 bound”
3. Adnan- how did you come up with
“1.5 ng/mL to 8 ng/mL is a free to total PSA ratio = 18.75%.”
I am sorry for the little detail, Iam just doubting myself because everyone has different values.
From the stem of the question:
Free PSA 0.5ng/ml. Total PSA 9ng/ml (yield bound PSA 8.5ng/ml )
Free PSA : Total PSA ratio = 0.5/9 = 0.055
The ratio is less then 0.1, means that the index patient has a 57.7% chance of a positive needle biopsy for prostate cancer. (Answer C)
Side note: It sounds like 57.7% that the patient will get prostate cancer. If I were a patient hearing this I would be freak out too like you’ve mentioned Rodo. But like Dr Archer said, “probability ( likelihood) of an etiology does not equate drawing conclusions.”
Please look at link below provided by Adnan.
http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81944