Improving the Measurement of Surgical Site Infection Risk Stratification/Outcome Detection

Exhibits 65 to 67

Exhibit 65. Results of logistic regression using the derivation dataset for only total knee surgery

Variable Estimate tValue Probability
Intercept -6.27 -3.13 0.0025
Charlson score* 0.32 2.03 0.0423
General anesthesia -0.48 -1.22 0.2231
Male 0.90 2.20 0.0280
History of MRSA 1.49 2.69 0.0071
Postop admission 2.97 4.83 0.0000
Postop hematocrit 0.06 0.86 0.3922
Preop hematocrit 0.09 0.57 0.5742
Preop hemoglob -0.50 -1.09 0.2835
Surgery duration 0.00 1.25 0.2104

*Additional Intermountain risk factor.

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Exhibit 66. Results of logistic regression using the validation dataset for only total knee surgery

Variable Estimate tValue Probability
Intercept -3.76 -2.23 0.0256
Charlson score* -0.51 -1.75 0.0793
General anesthesia 0.53 1.33 0.1819
Male 0.60 1.70 0.0896
History of MRSA 2.12 4.45 0.0000
Postop admission 1.74 4.66 0.0000
Postop hematocrit -0.01 -0.10 0.9173
Preop hematocrit 0.06 0.54 0.5918
Preop hemoglob -0.37 -1.11 0.2670
Surgery duration 0.01 1.64 0.1007

*Additional Intermountain risk factor.

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Exhibit 67. Results of logistic regression using the combined dataset for only total knee surgery

Variable Estimate tValue Probability
Intercept -4.57 -3.79 0.0002
Charlson score* 0.03 0.19 0.8475
General anesthesia 0.11 0.43 0.6692
Male 0.73 2.75 0.0059
History of MRSA 1.76 5.01 0.0000
Postop admission 2.15 6.99 0.0000
Postop hematocrit 0.02 0.46 0.6493
Preop hematocrit 0.04 0.37 0.7176
Preop hemoglob -0.33 -1.08 0.2875
Surgery duration 0.00 1.78 0.0759

*Additional Intermountain risk factor.

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Page last reviewed December 2012
Internet Citation: Exhibits 65 to 67. Content last reviewed December 2012. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/research/findings/final-reports/ssi/ssiexh65-67.html