PSA vs Digital Rectal?

[fuzzywuz]

---

Members don't see this ad.

So I have this question and I don't understand why my answer is wrong. I can understand Kaplan's rationale, but I'm curious if I can actually be right.

The problem gives me information about this man w/ blastic changes on XR. Clearly they are talking about Prostate Ca. Anyway, the question is asking me for the next appropriate step after looking at the XR.

I am down to PSA and digital rectal exam. Why would you do a digital rectal exam as the next step? I feel like, PSA levels would be obtained eventually so why not get it first. In fact, DREs will throw off the PSA value. However, the explanation states that they would use PSA as a marker for treatment progress.

But in real life, don't you always do a PSA first followed by a rectal?

I guess more importantly, what would the NBME do?

 

[justaregularmed]

So I have this question and I don't understand why my answer is wrong. I can understand Kaplan's rationale, but I'm curious if I can actually be right.

The problem gives me information about this man w/ blastic changes on XR. Clearly they are talking about Prostate Ca. Anyway, the question is asking me for the next appropriate step after looking at the XR.

I am down to PSA and digital rectal exam. Why would you do a digital rectal exam as the next step? I feel like, PSA levels would be obtained eventually so why not get it first. In fact, DREs will throw off the PSA value. However, the explanation states that they would use PSA as a marker for treatment progress.

But in real life, don't you always do a PSA first followed by a rectal?

I guess more importantly, what would the NBME do?

As far as PSA goes it only really supports the diagnosis. Every male eventually gets a big prostate and their PSA will probably go up. If you had a baseline and then see a big swing that's obviously not good and warrants further investigation. Rectal exam is quick, cheap, and easy you can feel lumpy bumpy or just big old prostate. Although I cant recall for sure I thought you needed a biopsy to show loss of basal cell layer to confirm the diagnosis.

.

 

[tco]

I thought that PSA was not increased by DRE unless the patient had prostatitis, which is a condition that it is contraindicated for.

To answer your question, I would think that PSA levels would be the answer. You look at the difference between free and bound PSA to hint at either BPH or prostate cancer.

 

[fuzzywuz]

The other part of the explanation states that DRE is cheaper than the PSA. Supposedly you get more out of the DRE than PSA for the cost.

The interesting caveat is that they also mentioned that the DRE can detect a hard stoney mass if the ca is in the advance stages. With that, I think they should change the answer because we can't always assume even w/ a negative DRE that the patietn doesn't have cancer. Eventually, they WILL have to get that PSA (even if they don't have a baseline).

In fact, aren't PSAs part of an annual check-up? I know my dad gets one every year.

 

[ILikeSugar]

But in real life, don't you always do a PSA first followed by a rectal?


I guess more importantly, what would the NBME do?

In real life, you would do the DRE while the patient was in your office and then send him to the lab on a later date ("massage" can increase PSA levels).

The correct NMBE solution is a bit tougher. Are you sure that the image indicates that it HAS to be cancer and not BPH, etc? If this is true, then getting the PSA could help confirm your suspicion.
However, I would go check out the image to see if it could be ambiguous. If there is any ambiguity, then DRE would be a must to determine if it is hard/soft/nodular etc.

good luck!

 

[kl323]

In real life, you would do the DRE while the patient was in your office and then send him to the lab on a later date ("massage" can increase PSA levels).

The correct NMBE solution is a bit tougher. Are you sure that the image indicates that it HAS to be cancer and not BPH, etc? If this is true, then getting the PSA could help confirm your suspicion.
However, I would go check out the image to see if it could be ambiguous. If there is any ambiguity, then DRE would be a must to determine if it is hard/soft/nodular etc.

good luck!

This problem is tricky. I saw this problem and felt PSA would be a logical choice. At least I'm not alone on this!

 

[ArcGurren]

PSA is sensitive but not specific (it can also be a sign of BPH for example)

Digital rectal exam can be a lot more specific - a rock hard nodule for example is a better indicator that something is very wrong with the prostate.

 

[DrBB]

Goljan talks about this exact situation. You always do a DRE first because it is 1) much cheaper and quicker and 2) more specific.

Also, according to Goljan, a DRE will NOT throw off the PSA values since PSA is mostly intracellular.

 

[RapplixGmed]

DRE is cheaper and more specific than PSA. PSA can be increased by a lot of stuff, and cancer is only one of them.

Goljan is right. Don't worry about increasing PSA after DRE:

According to up to date:

Any perineal trauma can increase the serum PSA. DRE may cause minor transient elevations that are clinically insignificant. As an example, one study of 2750 healthy men over the age of 40 undergoing DRE divided patients into four groups based upon their initial serum PSA. The two groups with the lowest initial serum PSA values (0.1 to 4 and 4.1 to 10 ng/mL) had statistically insignificant changes in the serum PSA after DRE, while PSA increases in the group with an initial serum PSA 10.1 to 20 ng/mL showed a trend toward statistical significance, and those with an initial serum PSA greater than 20 ng/mL had statistically significant increases after DRE. The PSA increase in the two groups with the highest serum values was not clinically relevant, since they did not change ultimate management. Thus, it is reasonable to perform PSA testing without regard to whether a patient has had a recent DRE.

 

[tco]

That makes sense.

DRE followed by transrectal biopsy.

 

[justaregularmed]

That makes sense.

DRE followed by transrectal biopsy.

As i said in the second post 👍 I'll speak more sophisticated like next time so people listen.

 

[tco]

As i said in the second post 👍 I'll speak more sophisticated like next time so people listen.

I didn't even see your post. Sorry.

 

[justaregularmed]

I didn't even see your post. Sorry.

And if it comes up loss of the basal cell layer == cancer.

Clinical management is more step 2 ish, I wonder what Kaplan was thinking.