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Appendix V. JAMIA Draft Manuscript Tables

Table 1. Number of Procedures Stratified by Hospital and Types between 2008 and 2009

 DHIHVA SLCHCSVVMC
Procedure Num.% Proc.Num.% Proc.Num.% Proc.Num.% Proc.
CABGTotal Procedures0 1845 78 0 
  sSSI0 120.7%33.8%0 
  dSSI0 70.4%00.0%0 
  oSSI0 10.1%00.0%0 
 Total SSI0 201.1%33.8%0 
HERNIATotal Procedures898 1059 237 294 
  sSSI40.4%00.0%20.8%10.3%
  dSSI20.2%00.0%00.0%00.0%
  oSSI10.1%00.0%10.4%00.0%
 Total SSI70.8%00.0%31.3%10.3%
THATotal Procedures268 2810 90 137 
  sSSI20.7%00.0%00.0%00.0%
  dSSI20.7%50.2%00.0%10.7%
  oSSI31.1%30.1%22.2%00.0%
 Total SSI72.6%80.3%22.2%10.7%
TKATotal Procedures232 7897 163 421 
  sSSI10.4%60.1%00.0%00.0%
  dSSI20.9%70.1%00.0%10.2%
  oSSI10.4%20.0%10.6%00.0%
 Total SSI 41.7%150.2%10.6%10.2%

Abbreviations: CABG, coronary artery bypass grafting; HERNIA, herniorraphy; TKA, total knee arthroplasty; THA, total hip arthroplasty; sSSI, superficial SSI; dSSI, deep SSI; oSSI, organ space SSI

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Table 2. Component rules of the rpart, inclusive, and simple algorithms

CABGAll of the following:
Presence of a post-operative culture, and
Post-operative antibiotics were given, and
Maximum post-operative leukocyte count is not less than 11.85
HerniorrhaphyEither of the following:
Presence of a post-operative culture and
   Maximum post-operative leukocyte count is not less than 7.78
Absence of a post-operative culture and one of the following criteria:
   Post-operative antibiotics given and any post-operative leukocyte count test drawn
   Post-operative antibiotics not given, but the patient had a post-operative admission
Total Knee Arthroplasty:Either of the following:
Presence of a post-operative culture, or
Presence of a c-reactive protein and the maximum post-operative leukocyte count is not less than 9.45
Total Hip Arthroplasty:All of the following:
Presence of a post-operative culture, and
Post-operative antibiotics were given, and
Maximum post-operative leukocyte count is not less than 7.55
“Inclusive” algorithm:Any one of the following:
Erythrocyte sedimentation rate greater than 20, or
Total neutrophil count greater than 5,000/mm3, or
Total leukocyte count greater than 9,000/mm3, or
C-reactive protein greater than 3mg/dL, or
Any post-operative antibiotics given, or
Presence of a post-operative culture, or
Patient was readmitted within 30 days post-operatively
“Simple” algorithm:Either of the following:
Microbiology test ordered between post-operative days 4 and 30 (inclusive), or
An antibacterial was prescribed between post-operative days 4 and 30 (inclusive)

Abbreviations: CABG, coronary artery bypass grafting

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Table 3. Performance of Different Algorithms by SSI Type on the Training Set.

 Total SurgeriessSSIdSSIoSSI
Total3555137410638
 # Flagged (% Total)
 
# True Positives Caught (% Sensitivity)
Rpart Algorithm2709 (7.6%)156 (41.7%)101 (95.3%)34 (89.5%)
Inclusive Algorithm7961 (22.4%)328 (87.7%)104 (98.1%)35 (92.1%)
Simple6939 (19.5%)318 (85.0%)103 (97.2%)34 (89.5%)

Abbreviations: SSI = surgical site infection. sSSI = superficial SSI. dSSI = deep SSI. oSSI = organ-space SSI

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Table 4. Performance of Different Algorithms by SSI Type on the Test Set.

 Total SurgeriessSSIdSSIoSSI
Total27,7392797533
 # Flagged (% Total)
 
# True Positives Caught (% Sensitivity)
Rpart Algorithm2034 (7.3%)126 (45.2%)54 (72.0%))25 (75.8%)
Inclusive Algorithm8,685 (31.3%)251 (90.0%)75 (100%)30 (90.9%)
Simple5318 (19.2%)230 (82.4%)68 (90.7%)30 (90.9%)

Abbreviations: SSI = surgical site infection. sSSI = superficial SSI. dSSI = deep SSI. oSSI = organ-space SSI.

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Table 5. Accuracy of algorithm at each participating hospital

Accuracy of Algorithm at DHAccuracy of Algorithm at IH
  Routine Surveillance   Routine Surveillance 
Algo SSIno SSITotalAlgo SSIno SSITotal
SSI67177SSI9704713
no SSI713451352no SSI161085710873
Total1314161429Total251156111586
          
 Sensitivity46.2% Sensitivity36.0%
 Specificity95.0% Specificity93.7%
 Positive Predictive Value7.8% Positive Predictive Value1.3%
 Negative Predictive Value99.5% Negative Predictive Value99.9%
Accuracy of Algorithm at VA SLCHCSAccuracy of Algorithm at VVMC
  Routine Surveillance   Routine Surveillance 
Algo SSIno SSITotalAlgo SSIno SSITotal
SSI23335SSI01717
no SSI2531533no SSI3832835
Total4564568Total3849852
          
 Sensitivity50.0% Sensitivity0.0%
 Specificity94.1% Specificity98.0%
 Positive Predictive Value5.7% Positive Predictive Value0.0%
 Negative Predictive Value99.6% Negative Predictive Value99.6%

Abbreviations: SSI = surgical site infection; Algo, algorithm

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Table 6. Algorithm Sensitivity (Sn) by Surgical Procedure Type.

 DHIHVA SLCHCSVVMC
 TPFNSN (%)TPFNSN (%)TPFNSN (%)TPFNSN (%)
CABGNANANA4450.0%00NA00NA
HERNIA3350.0%00NA10100.0%010.0%
HIP1325.0%3537.5%020.0%010.0%
KNEE2166.7%2722.2%10100.0%010.0%
Total6746.24450.02250.0030.0

Abbreviations: CABG, coronary artery bypass grafting; HERNIA, herniorraphy; HIP, total hip arthroplasty; KNEE, total knee arthroplasty; NA, not applicable; TP, true positives; FN, false negatives; Sn, sensitivity

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Table 7. Accuracy of Adjudicated Algorithm at Each Participating Hospital

Accuracy of Adjudication at DHAccuracy of Adjudication at IH
  Routine Surveillance   Routine Surveillance 
Adjudicated SSIno SSITotalAdjudicated SSIno SSITotal
SSI61.427.42SSI90713
no SSI314101348no SSI161155911575
Total91411.41420.4Total251155911584
          
 Sensitivity66.7% Sensitivity36.0%
 Specificity99.9% Specificity100.0%
 Positive Predictive Value80.9% Positive Predictive Value100.0%
 Negative Predictive Value99.8% Negative Predictive Value99.9%
Accuracy of Adjudication at VA SLCHCSAccuracy of Adjudication at VVMC
  Routine Surveillance   Routine Surveillance 
Adjudicated SSIno SSITotalAdjudicated No Change 
SSI2435    
no SSI2560562    
Total4564568    
          
 Sensitivity50.0%   
 Specificity99.3%   
 Positive Predictive Value33.37%   
 Negative Predictive Value99.6%   

This table also removes surgeries that were considered invalid after manual review.

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Current as of December 2012
Internet Citation: Appendix V. JAMIA Draft Manuscript Tables. December 2012. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/research/findings/final-reports/ssi/ssiapvtables.html