title: Quantitative estimates of the variability of in vivo sonographic measurements of the mouse aorta for studies of abdominal aortic aneurysms and related arterial diseases.
abstract: OBJECTIVE
  Burgeoning interest in reducing the morbidity and mortality associated with abdominal aortic aneurysms (AAAs) has led to experimental strategies to elucidate the disease process and attain pharmacologic regression using the apolipoprotein E(-/-) (ApoE(-/-)) mouse model of angiotensin-induced AAAs and in vivo sonography. However, the variability of in vivo sonographic measurements of the mouse aorta has not been established. Thus, our purpose was to determine quantitative estimates of the variability of in vivo sonographic measurements of the mouse aorta as a guide for the design and assessment of studies focused on regression of AAAs and related arterial diseases.
  
  
  METHODS
  We used Bland-Altman, locally weighted scatterplot-smoothing regression, and resampling (bootstrapping) methods for variability analyses of multiple in vivo short- and long-axis sonographic measurements of ApoE(-/-) mouse aortas. We measured distinct aortic sites in vivo at the baseline and after angiotensin-induced AAAs and ex vivo using digital calipers.
  
  
  RESULTS
  We analyzed 236 data points from 10 male mice (14 weeks old; mean weight ± SD, 29.7 ± 1.6 g). Overall intramouse differences between short- and long-axis and in vivo and ex vivo measurements were 0.038 (95% confidence interval [CI], 0.031-0.046) and 0.085 (95% CI, 0.062-0.109) mm, respectively. Intermouse differences in short-axis measurements were 0.047 (95% CI, 0.042-0.053), 0.049 (95% CI, 0.044-0.055), and 0.039 (95% CI, 0.036-0.042) mm for infrarenal, suprarenal, and thoracic measurements, respectively; differences in long-axis measurements were 0.054 (95% CI, 0.044-0.064), 0.029 (95% CI, 0.024-0.034), and 0.046 (95% CI, 0.037-0.054) mm. Bland-Altman and locally weighted scatterplot-smoothing analyses showed excellent agreement between measures with no variation in discrepancies vis-à-vis the target measurement.
  
  
  CONCLUSIONS
  These data establish previously undefined estimates of measurement variability relevant for in vivo sonographic studies of AAA regression in a commonly studied mouse model.
authors.affiliation: Department of Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA. uchechukwu.sampson@vanderbilt.edu
authors.forename: Uchechukwu K
authors.initials: UK
authors.lastname: Sampson
authors.forename: Prudhvidhar R
authors.initials: PR
authors.lastname: Perati
authors.forename: Petra A
authors.initials: PA
authors.lastname: Prins
authors.forename: Wellington
authors.initials: W
authors.lastname: Pham
authors.forename: Zhouwen
authors.initials: Z
authors.lastname: Liu
authors.forename: Frank E
authors.initials: FE
authors.lastname: Harrell
authors.forename: MacRae F
authors.initials: MF
authors.lastname: Linton
authors.forename: John C
authors.initials: JC
authors.lastname: Gore
authors.forename: Valentina
authors.initials: V
authors.lastname: Kon
authors.forename: Sergio
authors.initials: S
authors.lastname: Fazio
mesh_terms: D000818:Animals; D001011:Aorta / Q000000981:diagnostic imaging*; D017544:Aortic Aneurysm, Abdominal / Q000000981:diagnostic imaging*; D001157:Arterial Occlusive Diseases / Q000000981:diagnostic imaging*; D004452:Echocardiography / Q000379:methods*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity