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. 2015 Mar;261(3):443-4.
doi: 10.1097/SLA.0000000000000850.

Postoperative venous thromboembolism outcomes measure: analytic exploration of potential misclassification of hospital quality due to surveillance bias

Jeanette W Chung  1 , Mila H Ju, Christine V Kinnier, Min-Woong Sohn, Karl Y Bilimoria
Affiliations

Postoperative venous thromboembolism outcomes measure: analytic exploration of potential misclassification of hospital quality due to surveillance bias

Jeanette W Chung et al. Ann Surg. 2015 Mar.
No abstract available

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Figures

Figure 1
Figure 1. Hypothetical Illustration of Hospital Misclassification Due to Surveillance Bias in PSI12
Figure 1 illustrates hypothetical PSI12 and VTE imaging rates for two hypothetical hospitals, “X” and “Z.” The x-axis shows the number of patients in the denominator. The primary y-axis shows the true underlying incidence of clinically-significant VTE (dark-shaded region) and subclinical VTE (light-shaded region) per 100 patients in the denominator. The secondary y-axis shows the number of patients that receive VTE imaging per 100 patients in the denominator. By construction, Hospital-X has better VTE outcomes (20% incidence of clinically-significant VTE) than Hospital-Z (40% incidence of clinically-significant VTE). Both hospitals have 30% incidence of subclinical VTE. At 10% surveillance rates (LINE A), both hospitals have the same PSI12 rate: 10%. This is misleading because both hospitals are not of equal quality, and because this underestimates true underlying incidence of clinically-significant VTE in both hospitals (Hospital-X: 20%; Hospital-Z: 40%). At 20% surveillance rates (LINE B), both hospitals have PSI12 rates of 20%. Again, this is misleading because both hospitals are not equal, and because this is an underestimate of Hospital-Z's true VTE incidence. At 40% surveillance (LINE C), both hospitals have PSI12 rates of 40%. This is misleading because it inflates the incidence of clinically-significant VTE in Hospital-X by capturing 20 cases of subclinical VTE. At 100% screening (LINE D), Hospital-X has a PSI12 rate of 50% and Hospital-Z has a PSI12 rate of 70%. While this accurately shows Hospital-X to have better VTE outcomes than Hospital-Z, both PSI12 rates are inflated estimates of the true underlying incidence of clinically-significant VTE in each hospital due to surveillance bias and the inability to identify and exclude subclinical VTE from the numerator of PSI12.
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References

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