Table 3.

Example of a final rule set to determine indication for biopsy

Rule No.	Rule	Decision	Historical No. of patients that correctly satisfy specific rule	Historical No. of patients that correctly satisfy all rules
1	Composition of nodule is entirely solid	Likely nonbenign—recommend biopsy	12/12	12/12
	LNs appear normal
	Tumor is unifocal
2	Nodule > 50% cystic	Likely benign-defer biopsy	7/7	19/19
	Margin is regular
	LNs appear normal
3	Composition of nodule is entirely solid	Likely nonbenign–recommend biopsy	4/4	23/23
	Hypoechoic halo is either absent OR complete but not partial
	Margin is irregular/microlobulated/ spiculated
4	Composition of nodule is entirely solid	Likely nonbenign–recommend biopsy	9/10	32/33
	Margin is indistinct
	Tumor is unifocal OR multifocal (unilaterally)
5a	Composition of nodule is mixed solid/ cystic < 50% cyst	Likely benign–defer biopsy	10/11	42/44
	Hypoechoic halo is absent OR complete (ie, not absent)
	Tumor is unifocal OR multifocal (bilaterally)
6	Composition of nodule is entirely solid	Likely nonbenign—recommend biopsy	6/7	48/51
	LNs are enlarged but normal appearing OR are suspicious for metastasis
7a	LNs are not visualized or are visualized contralateral to primary tumor (but not ipsilaterally)	Likely benign—defer biopsy	3/4	51/55
	Tumor is multifocal (unilaterally)
8	Composition of nodule is entirely solid	Likely nonbenign—recommend biopsy	3/4	54/59
	Margin is indistinct
	Tumor is multifocal and bilateral
9	Otherwise	Likely nonbenign—recommend biopsy	3/8	57/67

Abbreviation: LN, lymph node.

aThese misclassification are the least acceptable type of error—patients classified as likely benign when they were not.