Original article
Reliability of a standardized protocol to calculate cross-sectional chest area and severity indices to evaluate pectus excavatum

https://doi.org/10.1016/j.jpedsurg.2006.03.003Get rights and content

Abstract

Purpose

In evaluating the impact of surgical repair of pectus excavatum, the Haller index developed for preoperative decision-making purposes may be inadequate to quantify postoperative changes in shape of the chest. Individual patients may also have chest characteristics that impact the success of repair, many of which would be unlikely to be measured by the Haller index alone. We have developed a protocol that measures the cross-sectional chest area and the asymmetry index along with the Haller index to more completely quantify the nature of the deformity. The purpose of this study was to determine the reliability of this protocol in the interpretation of chest computed tomography images from multiple sites. The protocol was developed as part of a multicenter study of clinical outcomes after surgical repair of pectus excavatum.

Methods

Two radiologists independently selected 5 images from each of 32 computed tomography scans from multicenter study participants according to the protocol. A digitizer was used to measure the diameters and cross-sectional areas of the images selected; these results were used to calculate the Haller and asymmetry indices. The protocol was tested for intradigitizer and interradiologist reliability. Using the Haller and asymmetry indices, we also assessed agreement between radiologists classifying patients as abnormal.

Results

Agreement was uniformly high for all comparisons (all Lin's concordance coefficients >0.99 and all Cohen's κ's >0.85, all agreement on classification of patients >95%) indicating almost perfect agreement. Disagreement on classification of patients using the Haller and asymmetry index was at the cut points for abnormality.

Conclusion

The protocol was found to be a highly reliable method for deriving the cross-sectional area of the chest and the Haller and asymmetry indices and for classifying patients for surgical eligibility. Borderline cases should be examined carefully to determine the appropriateness of surgical intervention. Cross-sectional area can be measured reliably using this protocol and thus may be useful in quantifying the success of surgical intervention.

Section snippets

Subjects

All participants in the multicenter study signed an informed consent that was in compliance with the human experimental guidelines of the United States Department of Health and Human Services and of the Eastern Virginia Medical School Institutional Investigation Review Board. The 32 participants were predominately male (91%), and the average age was 13.2 years (range, 6.1-19.7 years). Because of the timing of this reliability study early in the multicenter study, all 32 patients were from the

Results

The protocol used by the radiologists included detailed instructions on how to select the appropriate 5 images (see Methods). Each of the 32 scans had up to 6 pages of images that could be selected for calculation of pectus defect severity. Reliability between the 2 radiologists was entirely dependent on the images chosen and the impact of any differences in the images on the raw measurements. The 2 radiologists chose within 1 image of each other most of the time (81%; n = 160) and were within

Discussion

The 5-position standard protocol was proposed to alleviate potential biases and inconsistencies in data being collected from multiple centers with competing surgical treatments. Although the protocol is more extensive than just determining a single Haller index as a rough gauge of severity, it provides a tool for assessing both the need for surgery and the outcome of repair in any future quality monitoring program or to readily study any potential future modifications of surgical technique. To

References (8)

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    Therefore, the patient with a deep chest that is narrow side-to-side can have an impressively severe pectus excavatum defect, which when assessed by the HI, generates a number that is nowhere near the historically chosen value of 3.25. With recent literature we can conclude that a HI of 3.25 as a cut-off point for surgical intervention is no longer a good discriminator and bares no conclusive relationship with the aesthetic complaints observed.6,20–23 In addition to this inadequacy, other limitations of the HI includes variation with thoracic shape/age/gender/breathing, lack of consideration for asymmetry, and lack of consideration for cardiac compression.4,20–31

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