Exhibit 8. Distribution of SSI among surgeries in VASQIP data
| CABG | HERNIA | KNEE | HIP | TOTAL | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Total Procedures | 4525 | 19692 | 7467 | 3867 | 35551 | |||||
| Surgical Site Infections | #SSI | % Total | #SSI | % Total | #SSI | % Total | #SSI | % Total | #SSI | % Total |
| sSSI | 108 | 93.1 | 165 | 74.7 | 61 | 59.2 | 40 | 51.3 | 374 | 72.2 |
| dSSI | 8 | 6.9 | 36 | 16.3 | 29 | 28.2 | 33 | 42.3 | 106 | 20.5 |
| oSSI | 0 | 0.0 | 20 | 9.0 | 13 | 12.6 | 5 | 6.4 | 38 | 7.3 |
| Total | 116 | 221 | 103 | 78 | 518 |
SSI = surgical site infections, VASQIP = Veterans Affairs-Surgical Quality Improvement Program, CABG = coronary artery bypass grafting, HERNIA = herniorraphy, KNEE = total knee arthroplasty, HIP = total hip arthroplasty, #SSI = number of SSI, % Total = percent of all SSI, sSSI = superficial SSI, dSSI = deep SSI, oSSI = organ space SSI
Exhibit 9. Preliminary performance on VASQIP training set
| CABG | HERNIA | KNEE | HIP | |||||
|---|---|---|---|---|---|---|---|---|
| Total Cases | 4525 | 19692 | 7467 | 3867 | ||||
| Positive SSI | TP8 | FN0 | TP52 | FN4 | TP39 | FN3 | TP36 | FN2 |
| Negative SSI | FP402 | TN4115 | FP1004 | TN18632 | FP873 | TN6552 | FP295 | TN3534 |
| ID by Alg | 410 | 4115 | 1056 | 18636 | 912 | 6555 | 331 | 3536 |
| % Excluded by Alg | 90.94 | 94.64 | 87.79 | 91.44 | ||||
| Diagnostic Accuracy | ||||||||
| Sensitivity | 100.00% | 92.86% | 92.86% | 94.74% | ||||
| Specificity | 91.10% | 94.89% | 88.24% | 92.30% | ||||
| PPV | 1.95% | 4.92% | 4.28% | 10.88% | ||||
| NPV | 100.00% | 99.98% | 99.95% | 99.94% | ||||
| AUROC | 95.60% | 93.90% | 90.50% | 93.50% | ||||
| Time Saving | ||||||||
| NNR w/Alg | 51.25 | 20.31 | 23.38 | 9.19 | ||||
| NNR s/Alg | 555.56 | 357.14 | 178.57 | 102.04 | ||||
Alg = algorithm, AUROC = area under receiver-operator curve, CABG = coronary artery bypass grafting, HERNIA = herniorraphy, ID = identified, KNEE = total knee arthroplasty, HIP = total hip arthroplasty, NNR= number needed to read, NPV = negative predictive value, PPV = positive predictive value.
Exhibit 10. Performance of different algorithms by SSI type on the training set
| Total Surgeries | sSSI | dSSI | oSSI | ||
|---|---|---|---|---|---|
| Total | 35551 | 374 | 106 | 38 | |
| Surgeries Flagged | # Caught (Sensitivity) | ||||
| Rpart Algorithm | 2709 (7.6%) | 156 (41.7%) | 101 (95.3%) | 34 (89.5%) | |
| Inclusive Algorithm | 7961 (22.4%) | 328 (87.7%) | 104 (98.1%) | 35 (92.1%) | |
| Simple | 6939 (19.5%) | 318 (85.0%) | 103 (97.2%) | 34 (89.5%) | |
SSI = surgical site infection. sSSI = superficial SSI. dSSI = deep SSI. oSSI = organ-space SSI. Inclusive algorithm looks for any high-normal value. Rpart algorithm refers to the algorithm derived using the Rpart procedure. ( ) = percentage of total
