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PTD - 185

Test Directory - CA125

Please note that for monitoring purposes results from Basildon and Southend are comparable, but results from other laboratories may differ due to methodological differences.


Carbohydrate Antigen 125

Clinical Indications

CA125 is raised in ovarian cancer but most adeno-carcinomas produce it.

Primary Care (NICE CG 122): CA125 should be measured in primary care if a woman (especially if 50 or over) reports having any of the following symptoms on a persistent or frequent basis particularly more than 12 times per month:
 - persistent abdominal distension (women often refer to this as 'bloating')
 - feeling full (early satiety) and/or loss of appetite
 - pelvic or abdominal pain
 - increased urinary urgency and/or frequency.

CA125 should also be measured in any woman of 50 or over who has experienced symptoms within the last 12 months that suggest irritable bowel syndrome (IBS), because IBS rarely presents for the first time in women of this age.

CA125 is a reliable marker for monitoring epithelial carcinoma of ovary. 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 trail..
CA125 may also be used as part of pre-op assessment for suspected ovarian malignancy. Its measurement in patients with pelvic masses may help differentiate malignant from benign lesions.
Recent evidence suggests that CA125 may be useful as a preoperative prognostic marker for transitional cell carcinoma of the bladder.

Request Form

Combined Pathology Blood form (Yellow/Black)


On request, 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 of bladder carcinoma.

Patient Preparation

Samples should not be taken from patients receiving therapy with high
biotin doses (i.e. > 5 mg/day) until at least 8 hours following the last biotin

Turnaround Time

Same day




2 ml


Yellow top (SST) tube

Causes for Rejection

Not meeting specific criteria for analysis.

Reference Range

Less than 35 kU/L

Half-life in Serum

Approx. 5 days.


Critical Difference 49%

Primary Care (NICE CG 122): If serum CA125 is 35 IU/ml or greater, an ultrasound scan of the abdomen and pelvis should be arranged. For any woman who has normal serum CA125 (less than 35 IU/ml), or CA125 of 35 IU/ml or greater but a normal ultrasound then assess her carefully for other clinical causes of her symptoms and investigate if appropriate. If no other clinical cause is apparent, advise her to return to her GP if her symptoms become more frequent and/or persistent.

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, pelvic inflammation).  Ovarian cancer cannot however be excluded and guidelines recommend ultrasound of abdomen and pelvis, particularly in those with relevant symptoms.

High concentrations of CA125 are more likely to be associated with malignancy; 98% of post-menopausal and 49% of pre-menopausal women with CA125 >70 kU/L have malignant disease

CA125 levels are >35 kU/L in 50% patients with stage I ovarian carcinoma and in over 90% of patients with stage II, III, or IV disease. Note however that since CA-125 may be normal in 50% of patients with stage 1 ovarian carcinoma, if suspicion is high despite a CA-125 <35kU/L, an ultrasound of the abdomen and pelvis is recommended.

CA-125 is raised in liver disease, 70% of patients with cirrhosis and 13% of patients with liver fibrosis have a raised CA-125. Moderately raised CA125 (usually < 100 kU/L).

Lab. Handling

Processing: Analysed from primary tube (CA12) and stored at 4C in the cold room (CB23).
(NO125 and save in separating freezer (CB40) at -20C, saved frozen rack)

Version 1.2 / November 2014                                                                                                 Approved by: Consultant Biochemist