Observer Variability of Iliac Artery Measurements in Endovascular Repair of Abdominal Aortic Aneurysms Brajesh K. Lal, MD, 1,2 Joaquim J. Cerveira, MD, 1,2 Craig Seidman, MD, 1 Paul B. Haser, MD, 1,3 Richard Kubicka, MD, 1 Zafar Jamil, MD, 1,3 Frank T. Padberg, MD, 1,2 Robert W. Hobson, MD, 1,3 and Peter J. Pappas, MD, 1,2 Newark and East Orange, New Jersey Accurate measurement of iliac arteries is essential for successful delivery of aortic endografts without iliac limb endoleak. Although intravascular ultrasound measurements may be reliable, they require an invasive procedure. Therefore, helical computed tomography (hCT) has become the most commonly used modality for obtaining preprocedure arterial diameter measurements. The accuracy of hCT remains ill-defined, however, because an anatomic gold standard with which to compare the measurements is not available. We therefore assessed inter- and intra- observer variability of hCT measurements. We also applied accepted cutoff measurements to determine the clinical impact of observer variability in predicting the need for adjunctive iliac access and iliac limb seal procedures. hCT scans were analyzed in 30 patients who had undergone successful placement of a bifurcated endograft (26 Ancure, 4 Aneurex). Mean age of patients was 75 years, the male/female ratio was 27:3. Three blinded observers measured transverse diameters (maximal aortic aneurysm [Amax], narrowest infrarenal aortic neck [Amin], maximal common iliac [Imax], and narrowest iliac artery [Imin]). Inter- and intraobserver vari- ability was calculated as standard deviation of mean pair differences according to the method of Bland and Altman. The true incidence of adjunctive procedures to facilitate delivery of the device into the aorta and ensure iliac limb seal was compared with that predicted by the observers to obtain sensitivity, specificity, and positive (PPV) and negative predictive value (NPV) for the measurements. Interobserver variability of iliac measurements was higher than intraobserver variability (p < 0.05). Interobserver variability of Amax ranged from 4.37 to 10.73% of the mean Amax. Conversely, variability of Amin was 8.91-18.89%, that of Imax was 12.11-22.23%, and that of Imin was 10.51-18.73% (p < 0.05 vs. Amax). Therefore, interobserver variability influ- enced aortic neck and iliac diameter twice as much as it did aneurysm measurements. To successfully place 30 endografts we performed 8 adjunctive access procedures (4 angiopla- sties, 4 common iliac artery conduits) and 17 adjunctive procedures in 60 limbs to ensure limb seal (9 unilateral IIA coil embolizations, 8 stents). We used 8.5 (Ancure) and 8.0 (Aneurex) mm as lower limits of acceptability for uncomplicated access, and 13.4 (Ancure) and 16 (Aneurex) mm as the upper limits of acceptability for uncomplicated iliac limb seal. These limits were applied to measurements from the three observers to predict need for adjunctive access or iliac seal procedures in this cohort. Sensitivity, specificity, PPV, and NPV of these observer mea- surements for a need to perform additional access procedures were 0.67, 0.80, 0.55, and 0.87; the same values for a need to perform additional seal procedures were 0.71, 0.74, 0.52, and 0.86, respectively. Interobserver variability was approximately 20% of measured iliac diameter. 1 Division of Vascular Surgery, Department of Surgery, University of Medicine and Dentistry of New Jersey–New Jersey Medical School, Newark, NJ, USA. 2 Section of Vascular Surgery, Veterans Administration, New Jersey Healthcare System, East Orange, NJ, USA. 3 Section of Vascular Surgery, Saint Michael’s Medical Center, Newark, NJ, USA. Presented at the 13th Annual Winter Meeting of the Peripheral Vascular Surgery Society, Steamboat Springs, CO, January 31-February 2, 2004. Correspondence to: Brajesh K. Lal, MD, Department of Surgery, Division of Vascular Surgery, University of Medicine and Dentistry of New Jersey–New Jersey Medical School, 185 South Orange Ave- nue, MSB H578, Newark, NJ 07103, USA, E-mail: lalbk@umdnj. edu Ann Vasc Surg 2004; 18: 644-652 DOI: 10.1007/s10016-004-0102-x Ó Annals of Vascular Surgery Inc. Published online: 6 October 2004 644