Warning

Background

CA 125 measurement is part of the ovarian cancer diagnostic pathway.

Ovarian cancer is the 5th most common malignancy in females.  It is usually diagnosed late with approximately 30% of cases having a palpable pelvic mass at presentation.  Symptoms are often non-specific abdominal symptoms but are characterised by their persistency and frequency.

When to test

Scottish Referral guidelines for suspected cancer recommend investigating patients who present with symptoms suspicious for ovarian cancer in:

Women >50yrs with new symptoms of irritable bowel syndrome (IBS)

Women >18 yrs with recurrent/persistent symptoms

  •  Bloating or abdominal distension
  •  Loss of appetite
  •  Feeling full quickly (early satiety) and /or loss of appetite
  •  Pelvic/abdominal pain
  •  Increased urinary frequency/urgency
  •  Change in bowel habit

First-line investigations include: 

  •  Abdominal palpation
  •  Urgent Pelvic ultrasound scan AND serum CA 125 (DO NOT MEASURE DURING MENSTRUATION)

CA125 may also be requested in the context of follow up/monitoring of patients with previously raised CA125 or monitoring of patients with known ovarian cancer (typically requested via secondary care)

When not to test

  • CA 125 should not be measured in any of the following situations:
  • During early pregnancy
  • During menstruation
  • For the investigation of suspected endometriosis
  • As part of a tumour marker screen 
    • CA 125 within the reference range does not exclude ovarian cancer
    • CA 125 may be raised in other malignancies in addition to other non-malignant pathologies 
  • In a male patient 

When to repeat a test

  • CA 125 should be repeated if:
    • It is mildly elevated and initial sample was collected during menstruation.
    • Directed by secondary care.
    • Presentation of new symptoms which are suggestive of ovarian cancer.

References and further reading

  1. Scottish Referral Guidelines for Suspected Cancer [Internet]. NHSScotland; 2019. Gynaecological Cancers; 2019 Jan 01 [cited 2022 Oct 04]. Available from: https://www.cancerreferral.scot.nhs.uk/gynaecological-cancers/?alttemplate=guideline

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Editorial Information

Last reviewed: 01/04/2023

Next review date: 01/04/2024

Author(s): Helen Falconer, Janet Hogg.

Version: 1

Approved By: National Demand Optimisation Group – Education Short Life Working Group and the Scottish Clinical Biochemistry Network (SCBN) Cancer Subgroup