A postmenopausal woman presents with pelvic mass, ascites, and elevated CA-125 of 320 U/mL. Risk of Malignancy Index (RMI) is calculated. Which formula correctly computes the RMI-1?
- A RMI = U × M × CA-125, where U = ultrasound score (0, 1, or 3), M = menopausal status (1 or 3), CA-125 in U/mL ✓
- B RMI = U × M × CA-125, where U = ultrasound score (1, 3, or 5), M = menopausal status (1 or 4)
- C RMI = (U + M) × CA-125, where U = 0 or 1, M = 1 or 3
- D RMI = U × CA-125 / M, adjusting for age-related menopausal risk
Explanation
RMI-1 (Jacobs et al., 1990) is calculated as U × M × CA-125, where U (ultrasound score) = 0 for no features, 1 for one feature, 3 for two or more features (features: multilocularity, solid areas, metastases, ascites, bilateral lesions); M (menopausal status) = 1 for premenopausal, 3 for postmenopausal; CA-125 is in U/mL. An RMI >200 has sensitivity ~85% and specificity ~97% for ovarian malignancy. Option B has incorrect ultrasound scoring values. Option C incorrectly adds rather than multiplies U and M. Option D divides by menopausal status, which is incorrect — postmenopausal patients receive a higher (not lower) multiplier because menopause increases risk.
Reference: Shaw's Textbook of Gynaecology, 17th ed.
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