Different devices used to test PSA

Dear Dr. Roach: I’m 77 and have an enlarged prostate. Recently, my internist had me take a PSA test, and it was 9.5 ng/mL. Two weeks later, my urologist did another test, and it was 5.7 ng/mL. The two tests were done by different lab groups. Are PSA scores calculated differently by different labs?

Answer:

T.W.

Yes, there are several different manufacturers who make devices to measure PSA levels, and each is slightly different. A 2021 study evaluating three of the most common devices showed that they were very similar (within 0.5 ng/mL of each other).

There are some reasons why PSA scores can suddenly become elevated. Inflammation or infection of the prostate can cause very large increases. I’d be surprised if that were the case, as it is likely you would have had symptoms.

Your level also decreased faster than I would expect it to without treatment.

There are times that labs can be spuriously high without an identifiable reason, and rechecking is always wise before making a clinical decision, especially when the change is unexpected.

Dear Dr. Roach: Iam a healthy 60-year-old woman of average height and weight with a single functioning kidney. (The other never developed.) I’ve never had any issues with the kidney that works, and tests have shown that it functions normally without the presence of disease or impairment.

Given my single kidney status, is it okay to drink 2-3 cups of caffeinated tea daily, or should I refrain? I’d like to retain normal kidney function for the rest of my life.

Answer:

Drink your tea with a clear conscience.

There isn’t good evidence that tea or caffeine in reasonable amounts is harmful to kidneys, and there’s some evidence that it may even be helpful at preventing kidney disease.

A plant-based diet, low salt and avoiding too many medicines that are harmful to the kidney — such as high-dose ibuprofen over the span of many years — are all great ways to protect your single kidney.