AboutNeha Dahiya MD Expertise I can help patients understand their lab report results, help them with queries regarding what pretest preparation is required. How often a follow up test needs to be done. What does a particular tissue biopsy report mean in everyday English. I can explain the biopsy or cytology procedure. I can deal with Histopathology / cytology / clinical pathology and clinical chemistry queries. Helping in this manner will be my contribution to the community.
Experience I am a pathologist and director of clinical laboratory services. I have been a practicing pathologist for last 9 years in a 350 bed multi specialty hospital laboratory.
Organizations Indian association of pathologists and microbiologists.
MIAC - Member International Academy of Cytology
International association of Pathologists - indian division
Indian association of Cytology
Question QUESTION: This is a question about the method used to report results from a Bayer Chemiluminescent test. Basically, what is the standard error of measure for this test? And two related questions: a) is a reported difference of 0.02 mg/ml statistically significant? b) by custom and normal usage is there a minimum amount of PSA reported instead of a descriptive phrase such as "no measurable amount"?
Thank you for your attention.
ANSWER: Hello Robert:
PSA is a screening test to assess the prostrate. PSA levels below 4.0ng/ml are considered normal. However there have been reports of cancer with PSA levels below 4.0 ng/ml
There is no specific normal or abnormal PSA level. Various factors, such as inflammation (e.g., prostatitis), physical activity etc can cause a man’s PSA level to fluctuate. PSA values can also vary somewhat from laboratory to laboratory. All equipment do not detect below the given normal range.
I am not sure what is the exact standard error in Bayer's method, but all labs report with upto 80 to 85% accuracy. This is because of systemic error introduced due to number of factors like - condition / service of equipment, type of reagents used, lot number of reagents, temp of reagents etc.
0.02ng/ml difference is not very significant. Every time you will be tested the value will be different. The value obtained is reported with a normal range or margin of error. What is more important is that is there a persistent increase in value. In addition it has to be correlated with age and clinical features
I hope I havent confused to with such a lengthy answer.
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QUESTION: Thanks for your reply. You are stating that the "reliability" of the Bayer PSA test is only 80-85% -- not very reliable for a test in my field. (Reliability has to do with the likelihood of receiving the same results from a repeat of the measure.) I conclude that the test results I was given -- 0.05 down to 0.02 are below the test's mathematical limits of discrimination. That is, this test is NOT reliable in distinguishing 0.00 from 0.02 or from 0.05. Do you agree?
I detect self-serving test marketeers here.
The issue of reliability is important to me because I had my prostate completely removed and there should be NO reliably detectable PSA discovered -- unless my operation was unsuccessful.
Thank you for your attention to my concern as well as my disgruntlement.
Answer Hi:
I would rather not comment on the reliabilty of equipment in specific labs.
under ideal conditions - equipment which is well maintained, all reagents are at optimal conditions the equipment should be able to give accurate measurements.
Three to four weeks Post radical prostatectomy the PSA levels should be zero or very close to zero and remain stable. If they are still high it indicates some tumor is left behind. If zero and at a later date PSA levels rise, it indicates a reappearance of tumor in the body.
In some patients a nerve sparing surgery where some amount of benign tissue is left behind, low but detectable levels of PSA are present.
