CA-125 levels are measured in a 58-year-old postmenopausal woman with a pelvic mass. The RMI (Risk of Malignancy Index) is calculated. Which formula is used to calculate RMI-I?
- A CA-125 × ultrasound features × CA-19.9
- B CA-125 alone with menopausal cutoff of 200 U/mL postmenopause
- C U × M × CA-125 (where U = ultrasound score 0/1/3, M = menopausal status 1 or 3) ✓
- D CA-125 / AFP ratio × ultrasound score
Explanation
The Risk of Malignancy Index (RMI), first described by Jacobs et al., is calculated as RMI = U × M × CA-125. The ultrasound score (U) assigns 0 for no morphological features, 1 for one feature, and 3 for two or more features (multiloculation, solid areas, bilateral lesions, ascites, intra-abdominal metastases). Menopausal status (M) assigns 1 for premenopausal and 3 for postmenopausal women. An RMI >200 has sensitivity ~70–80% and specificity ~90% for malignancy. Multiple versions exist (RMI-1 to RMI-4) with slight modifications to ultrasound scoring. This tool guides referral to gynecological oncology centers. The cutoff for referral per RCOG is RMI ≥250.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
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