CA125 (Tumour marker)

Chemical Pathology

Notes

CA125 is the most widely used tumour marker for epithelial ovarian cancer.

• It is used in the differential diagnosis of ovarian cysts and pelvic masses in postmenopausal women. CA125 should be used in conjunction with transvaginal ultrasound scans (TVUS) for the calculation of the Risk of Malignancy Index (RMI)
  
• It is measured in patients with ovarian cancer to assess response to chemotherapy and to detect tumour recurrence.
  
• Since the NICE guidelines for the early recognition of ovarian cancer were published in April 2011, it is now recommended that individuals who present in primary care with symptoms suggestive of ovarian cancer have a CA125 measurement, to determine the need for further investigations including pelvic and abdominal ultrasound scans.
  
• It is used to screen women with a family history of hereditary forms of ovarian cancer.
  
• CA125 should not be used for screening asymptomatic women.
  

Sample requirements

If patient on high dose biotin therapy (>5mg/day) collect sample at least 8 hours after the last dose.

For adults, 5 ml of blood taken into a 5 mL narrow gold top tube (or rust top for the Acute Unit)

Storage/transport

Send at ambient temperature to the laboratory. If unavoidable, samples can be stored refrigerated overnight.

Required information

Relevant clinical details.

Turnaround times

The assays are run on a daily basis Monday to Friday.

The in-lab turnaround time is less than 4 days

Reference ranges

Assayed using the Cobas Elecsys CA125 II ECLIA

Reference range: less than 35 kU/L*
*studies using the Cobas-Elecsys CA125 II ECLIA assay in 593 samples from healthy females (pre and post-menopausal) yielded a value of 35 kU/L (95th percentile).

kU/L = U/mL

Further information

• Lab Tests Online: CA 125 Test
  
• Monograph of the Association for Clinical Biochemistry and Laboratory Medicine (pdf)
  
• BMJ 2009; 339: b3527 Serum tumour markers: how to order and interpret them
  

Page last updated 20/09/2017