Risk of Malignancy Index (RMI) of Jacobs et al for Ovarian Tumors

Jacobs et al developed a Risk of Malignancy Index (RMI) for predicting the likely pathology of an ovarian or pelvic mass as benign or malignant.

Parameters:

(1) menopausal status

(2) ultrasound findings suggestive of malignancy

(3) serum CA125 (cancer antigen 125) in U/mL

Criteria for postmenopausal:

(1) amenorrhoea > 1 year, or

(2) women over 50 years of age with previous hysterectomy.

Ultrasound findings suggestive of malignancy:

(1) multi-loculated cysts

(2) evidence of solid areas

(3) evidence of metastases

(4) presence of ascites

(5) bilateral lesions

Parameter	Finding	Points
menopausal status	pre-menopausal	1
	post-menopausal	3
ultrasound findings suggestive of malignancy	none	0
	1	1
	>= 2	3

risk of malignancy index =

= (points for menopausal status) * (points for ultrasound findings) * (serum CA125 in U/mL)

The derivation of the formula from the equation for the likelihood ratio is given in the Jacobs (1990, Appendix page 929).

Interpretation:

• minimum score: 0

• maximum score: > 10,000

• The performance varies with the cutoff selected.

Performance at difference cutoffs for the RMI

NOTE: data for cutoffs at 75, 80 and 125 not shown.

Limitations:

• Morgante et al (1999) found that the RMI of Tinglustad et al (1996) gave better performance than the RMI of Jacobs et al.

• The prevalence of malignancy in the population would affect performance.

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