Lab

Cancer Antigen 125

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Cancer Antigen 125, CA-125, CA 125

  • Indications
  1. Postmenopausal pelvic mass evaluation
  2. Ovarian Cancer serial monitoring
  3. Not a Screening Test for cancer (insensitive)
    1. May obtain baseline if Ovarian Cancer high risk
  • Interpretation (CA 125 level in units/ml)
  1. Normal: CA-125 less than 35 (Does not exclude cancer)
  2. Increased
    1. CA-125 >35 highly correlated with cancer (epithelial Ovarian Cancer cell line)
      1. Used as oncology referral indication for post-menopausal women
    2. CA-125 >65 associated with cancer in 90% of pelvic masses
    3. CA-125 >200 unlikely to be due to benign condition
      1. Used as oncology referral indication for pre-menopausal women
  • Efficacy (ranges are approximate with high values more attributed to post-menopausal patients)
  1. Positive Predictive Value: 35-91%
  2. Negative Predictive Value: 67-90%
  3. Test Specificity
    1. Pre-Menopause: 71%
    2. Post-Menopause: 93%
  4. Test Sensitivity
    1. Pre-Menopause: 61%
    2. Post-Menopause: 90%
    3. Stage I disease: 50%
    4. Advanced disease: 90%