1. Resource utilization in coronary artery bypass operation: does surgical risk predict cost? 
Christopher J Riordan, MD, Milo Engoren, MD, Anoar Zacharias, MD, Thomas A Schwann, MD, Gary L Parenteau, MD, Samuel J Durham, MD, Robert H Habib, PhD 
The Annals of Thoracic Surgery 
Volume 69, Issue 4, Pages (April 2000)
DOI: /S (99)

2. Fig 1
Histogram of the frequency distribution of cost of coronary artery bypass grafting referenced to the median cost. Bell shaped curve indicates a near normal distribution of cost. Note, outlier patients (21 of 627) all with cost greater than 3 times median cost are lumped together.
The Annals of Thoracic Surgery  , DOI: ( /S (99) )

3. Fig 2
(A) The relationship between cost and length of hospital stay (LOS) from 607 coronary artery bypass graft patients (excluding 21 outliers), indicating a linear correlation corresponding to R2 = (B) Bland-Altman plot of the cost prediction error [error (%) = 100∗ (actual cost − estimated cost)/estimated cost] for each patient based on cost-LOS model depicted by regression line in panel A. These results indicate that LOS is an unbiased estimator of coronary artery bypass grafting cost (bias = 0.4%), but it can be quite inaccurate in individual patients as depicted by wide limits (∼50%) of agreement defined by bias ± 2S of the error.
The Annals of Thoracic Surgery  , DOI: ( /S (99) )

4. Fig 3
(A) The relationship between cost and The Society of Thoracic Surgeons Risk [STS risk (%)] from 607 coronary artery bypass graft patients (excluding 21 outliers) along with the linear regression results indicating a poor correlation (R2 = 0.12). (B) Bland-Altman plot of the cost prediction error [error (%) = 100∗ (actual cost − estimated cost)/estimated cost] for each patient based on cost-STS risk model depicted by regression line in panel A. These results indicate that STS risk is an unbiased estimator of coronary artery bypass grafting cost (bias = 0.4%), but it can be quite inaccurate in individual patients as depicted by wide limits (∼63%) of agreement defined by bias ± 2S of the error.
The Annals of Thoracic Surgery  , DOI: ( /S (99) )

5. Fig 4
(A) The relationship between length of stay (LOS) and The Society of Thoracic Surgeons Risk [STS risk (%)] from 607 coronary artery bypass graft patients (excluding 21 outliers) along with the linear regression results indicating a poor correlation (R2 = 0.09). (B) Bland-Altman plot of the LOS prediction error [error (%) = 100∗ (actual cost − estimated cost)/estimated cost] for each patient based on LOS-STS risk model depicted by regression line in panel A. These results indicate that STS risk is an unbiased estimator of LOS following coronary artery bypass grafting (bias = 0.4%), but it can be highly inaccurate in individual patients as depicted by the wide limits (∼95%) of agreement defined by bias ± 2S of the error.
The Annals of Thoracic Surgery  , DOI: ( /S (99) )

6. Fig 5
Prediction of coronary artery bypass graft cost from length of stay (LOS) (A) and STS risk (B), as well as LOS from STS risk (C) when patients were grouped into 6 patient cohorts, based on comparable risk as described in Table 1. Results indicate that cost-LOS, cost-STS risk and LOS-STS risk relationships, in sufficiently large patient cohorts, are all highly linear. These linear relationships provide simple models for predicting the impact of changes in clinical risk for the general coronary artery bypass graft population on expected costs.
The Annals of Thoracic Surgery  , DOI: ( /S (99) )