Table 2:

Mixed-effects Model with Unstructured Covariance and Time-to-Diagnosis Interactions with Imputed Data (100 Imputed Data Sets)

	Linear Mixed-effects Model with Log Transformation of Response
Effect	Percent Change*	P Value
Final pathology
Ductal carcinoma in situ	69 (30, 121)	<.001
Benign	REF
Time to diagnosis (y)	68 (56, 80)	<.001
Age at diagnosis (y)	1.2(0.1,2.2)	.03
Breast density
Fatty	−25 (−62, 48)	.40
Scattered fibroglandular	−25 (−54, 21)	.24
Heterogeneously dense	−24 (−52, 21)	.25
Extremely dense	REF
Race
Black	9.1 (−14,38)	.47
White	REF
Time-to-diagnosis interaction
Ductal carcinoma in situ	17 (0.5, 36)	.04
Benign	REF

Note.—Unless otherwise stated, data in parentheses are 95% confidence intervals. The response variable (long-axis length) was log transformed prior to model fitting. The variance-covariance estimates of the random effects are shown in Appendix E2 (online). REF = reference standard for calculations.

^*For each model coefficient $\widehat{\text{β}}$ estimated on the log-transformed scale, percent change on the natural scale was calculated as $\text{100}\cdot \left({\mathrm{e}}^{\widehat{\text{β}}}-1\right)$.