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OBJECTIVE: Pectus excavatum (PE) is the most common congenital anomaly of the chest wall. The Haller Index (HI), derived from a computed tomography (CT) of the chest, remains the standard for determining PE severity and is the basis for insurance approval of minimally invasive repair. The ability to accurately determine PE severity from two-way chest radiography (CXR) may provide substantial cost savings. As such, this study proposes to establish data-driven criteria for the use of CXR as a diagnostic modality in the preoperative evaluation of PE patients.
METHODS: A database of PE patients receiving preoperative CXR and CT from January 2003 to July 2012 was created. Haller indices were obtained from radiologic reports of CT scans. Two pediatric cardiothoracic surgeons, blinded from the CT HI scores, independently calculated CXR HIs. Inter-rater reliability, correlations, sensitivity, specificity, and accuracy were then calculated.
RESULTS: The database was comprised of 77 patients. A significant correlation was found between CXR HI estimates of the two observers, r=0.83. There were also significant correlations between the CXR and CT HI for observer 1, r=0.93 and for observer 2, r=0.77. CT HIs were used as the standard for identifying patients meeting surgical criteria (CT HI≥3.2). From this, sensitivities, specificities, and accuracies were calculated for the corresponding CXR HIs determined by each observer. Observer 1 CXR HI estimates had a sensitivity of 0.98, specificity of 0.82, and accuracy of 0.91. Observer 2 CXR HI estimates had a sensitivity of 0.93, specificity of 0.62, and accuracy of 0.78.
CONCLUSIONS: Utilizing the largest reported database of PE patients with both preoperative CXR and CT scan, we found a strong correlation between HIs calculated with each modality. Additionally, observed CXR HIs demonstrated good inter-rater reliability. While the sensitivity of CXR in diagnosing severe PE (CT HI ≥3.2) was high, specificity was less convincing. However, when only considering measured CXR HIs ≥3.75, combined specificity was quite high (0.93). Thus, we recommend replacing CT with CXR in the preoperative evaluation for patients with PE. CT should be used as a confirmatory test in those patients measured to have a CXR HI between 3.2-3.75.