A woman has elevated serum CA-125 and is suspected of having ovarian carcinoma. Which primary limitation reduces CA-125 utility as a screening marker in the general population?
- A Low specificity — CA-125 is also elevated in endometriosis, PID, and other benign conditions, producing many false positives ✓
- B CA-125 is only elevated in mucinous ovarian tumours, missing serous variants
- C CA-125 measurement requires tissue biopsy, making it invasive
- D CA-125 has a short serum half-life, making single measurements unreliable
Explanation
CA-125 (MUC16 mucin) is a large glycoprotein elevated in epithelial ovarian carcinoma (especially serous type), but it is also elevated in benign gynaecological conditions — endometriosis, PID, uterine fibroids — as well as in first-trimester pregnancy and other malignancies (pancreatic, endometrial, peritoneal). In premenopausal women, the false-positive rate renders it unsuitable for mass screening. CA-125 is elevated in serous (not just mucinous) ovarian carcinoma; mucinous carcinomas often express CEA instead. CA-125 is a serum test. Its half-life is approximately 4–5 days, which is adequate for clinical monitoring.
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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