Pathology Handbook



Carbohydrate Antigen 125

Clinical Indications

CA125 is raised in ovarian cancer but it is also produced by most adenocarcinomas.  CA125 is a reliable marker for monitoring epithelial carcinoma of ovary, but the specificity of the marker is such that it should not be used as a primary diagnostic test for ovarian carcinoma. 

Evidence for use of CA125 in early detection of familial ovarian carcinoma is limited and should be restricted to prospective clinical trials.

CA125 may also be used as part of pre-op assessment for suspected ovarian malignancy, in conjunction with clinical examination and imaging.  Measurement in patients with pelvic masses may help differentiate malignant from benign lesions, but masses close to the ovaries may be associated with misleadsingly high levels of this marker.

Recent evidence suggests that CA125 may be useful as a preoperative prognostic marker for transitional cell carcinoma of the bladder and in the follow-up of bladder cancer.  This is the only indication for carrying out this test in men.

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Analysed by referral laboratory if specific criteria met or requested by Consultant Gynaecologists or Oncologists.

Specific Criteria

Monitoring of therapy in ovarian carcinoma and pre-operative assessment of suspected ovarian malignancy (risk malignancy index). 

Pre-operative assessment and follow-up of bladder carcinoma.

NOTE:  If a patient is having serial tumour marker levels monitored the tests must all be done at the same laboratory as there are significant variations between assays

Turnaround Time

Run daily Monday to Friday




2 ml


Vacutainer gold top

Causes for Rejection

Not meeting specific criteria for analysis.

Reference Range

Less than 35 U/mL

Half-life in Serum

Approx. 5 days


  • Moderately raised CA125 (usually <100 kU/L) may be due to normal physiology (e.g. pregnancy or menstruation) or a benign process (e.g. endometriosis, benign ovarian cysts). 

  • High concentrations of CA125 are more likely to be associated with malignancy; 98% of post-menopausal and 49% of pre-menopausal women with CA125 >700 kU/L have malignant disease

  • High CA125 levels may be seen in patient with non-ovarian intra-abdominal malignancies, e.g. lymphoma

  • CA125 levels are >300 kU/L in 50% patients with stage I ovarian carcinoma and in over 90% of patients with stage II, III, or IV disease

  • CA-125 is raised in liver disease, 70% of patients with cirrhosis and 13% of patients with liver fibrosis have a raised CA-125.