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

Exhibits 29 to 31

Exhibit 29. Results of logistic regression using the 60-percent derivation set, including each of the five surgical procedures as a possible risk factor

Variable Estimate tValue Probability
Intercept -5.66922 -7.18334 0.00000
Admission transfer 0.249358 0.655373 0.51223
History of cancer 0.675356 1.234336 0.21708
Chronic kidney disease -2.28736 -2.24028 0.02507
General anesthesia 0.419425 1.499021 0.13387
Male 0.58722 2.677562 0.00742
History of MRSA 1.47331 4.87133 0.00000
Number of procedures 0.381148 3.171798 0.00151
Postop admission 2.104624 9.115523 0.00000
Postop hematocrit -0.04406 -2.01137 0.04496
Preop stay 0.042437 1.623837 0.10441
CABG surgery 0.24496 0.746911 0.45512
Herniorrhaphy 0.186762 0.564969 0.57209
Wound class 0.003031 0.014814 0.98818

CABG = coronary artery bypass grafting; MRSA = methicillin-resistant Staphylococcus aureus; Postop = postoperative; Preop = preoperative.

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Exhibit 30. Results of logistic regression using the 40-percent validation set, including each of the five surgical procedures as a possible risk factor

Variable Estimate tValue Probability
Intercept -5.9448 -7.7606 0.00000
Admission transfer -0.46026 -0.92513 0.35490
History of cancer -0.78305 -0.76388 0.44494
Chronic kidney disease -0.49964 -0.91168 0.36193
General anesthesia 0.046769 0.171229 0.86404
Male -0.08612 -0.3914 0.69550
History of MRSA 1.149853 3.048832 0.00230
Number of procedures 0.264643 1.861373 0.06269
Postop admission 2.115295 9.348542 0.00000
Postop hematocrit -0.01706 -0.79509 0.42677
Preop stay 0.035891 1.814288 0.06963
CABG surgery 0.725095 2.077166 0.03779
Herniorrhaphy 0.553825 1.787663 0.07383
Wound class 0.326074 1.904355 0.05686

CABG = coronary artery bypass grafting; MRSA = methicillin-resistant Staphylococcus aureus; Postop = postoperative; Preop = preoperative.

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Exhibit 31. Results of logistic regression using the combined derivation and validation sets, including each of the five surgical procedures as a possible risk factor

Variable Estimate tValue Probability
Intercept -5.75478 -10.6587 0.00000
Admission transfer -0.07527 -0.25258 -0.25258
History of cancer 0.186484 0.396676 0.69161
Chronic kidney disease -1.19328 -2.52852 0.01145
General anesthesia 0.248213 1.277382 0.20147
Male 0.254338 1.658706 0.09718
History of MRSA 1.347607 5.798036 0.00000
Number of procedures 0.322013 3.494699 0.00047
Postop admission 2.111179 13.10889 0.00000
Postop hematocrit -0.03231 -2.16588 0.03045
Preop stay 0.035145 2.315832 0.02057
CABG surgery 0.477163 2.015653 0.04384
Herniorrhaphy 0.376815 1.673907 0.09415
Wound class 0.16983 1.300158 0.19355

CABG = coronary artery bypass grafting; MRSA = methicillin-resistant Staphylococcus aureus; Postop = postoperative; Preop = preoperative.

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Page last reviewed December 2012
Internet Citation: Exhibits 29 to 31. December 2012. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/research/findings/final-reports/ssi/ssiexh29-31.html