Question

Mrs. Simpson, a 38-year-old female, presented for biopsy and excision of a recently discovered lump in her right breast. Along with her routine preoperative blood work, her physician requested a blood test for CA 27.29. Subsequent requests for CA 27.29 levels were made for her two-week post-op follow-up visit and at one year and two years following her surgery. Results are shown in the table below. All testing was performed by the same laboratory, using the same immunoassay instrumentation and reagent systems. Reference interval for CA 27.29 using this test system is 0–40 U/mL.

Sample	Result (U/mL)
Pre-op	602
2 weeks post-op	38
1 year post-op	41
2 years post-op	60

Issues and Questions to Consider

1. Why did the values fall after surgery?

2. Which value(s) indicate significant changes from the previous value?

3. How would interpretation of these results be affected if the laboratory had changed instrument manufacturers during the time period represented?

Answer 1

The CA27.29 is a glycoprotein MUC1 which raises when there is abnormal cells generally cancer cells.It rises sharply in breast cancer

Theses values falls down after chemotherapy and surgical intervention by removing the source if cancer cells As a result these tumor markers also comes down to normal gradually when all cancer cells are destroyed

The post op value done after 2 years shows a significant raise of the Tumor marker from the normal range in the 2 week and 2 year post op period

In case if there is a change of instrument manufacturer, the results may be varying depending upon the manufacturer's settings .This may even have out a wrong result.