ssiapvtables.htm

Appendix V. JAMIA Draft Manuscript Tables

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

			DH		IH		VA SLCHCS		VVMC
Procedure			Num.	% Proc.	Num.	% Proc.	Num.	% Proc.	Num.	% Proc.
CABG	Total Procedures		0		1845		78		0
		sSSI	0		12	0.7%	3	3.8%	0
		dSSI	0		7	0.4%	0	0.0%	0
		oSSI	0		1	0.1%	0	0.0%	0
	Total SSI		0		20	1.1%	3	3.8%	0
HERNIA	Total Procedures		898		1059		237		294
		sSSI	4	0.4%	0	0.0%	2	0.8%	1	0.3%
		dSSI	2	0.2%	0	0.0%	0	0.0%	0	0.0%
		oSSI	1	0.1%	0	0.0%	1	0.4%	0	0.0%
	Total SSI		7	0.8%	0	0.0%	3	1.3%	1	0.3%
THA	Total Procedures		268		2810		90		137
		sSSI	2	0.7%	0	0.0%	0	0.0%	0	0.0%
		dSSI	2	0.7%	5	0.2%	0	0.0%	1	0.7%
		oSSI	3	1.1%	3	0.1%	2	2.2%	0	0.0%
	Total SSI		7	2.6%	8	0.3%	2	2.2%	1	0.7%
TKA	Total Procedures		232		7897		163		421
		sSSI	1	0.4%	6	0.1%	0	0.0%	0	0.0%
		dSSI	2	0.9%	7	0.1%	0	0.0%	1	0.2%
		oSSI	1	0.4%	2	0.0%	1	0.6%	0	0.0%
	Total SSI		4	1.7%	15	0.2%	1	0.6%	1	0.2%

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

CABG	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 11.85
Herniorrhaphy	Either 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 Surgeries	sSSI	dSSI	oSSI
Total	35551	374	106	38
	# Flagged (% Total)	# True Positives 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%)

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 Surgeries	sSSI	dSSI	oSSI
Total	27,739	279	75	33
	# Flagged (% Total)	# True Positives Caught (% Sensitivity)
Rpart Algorithm	2034 (7.3%)	126 (45.2%)	54 (72.0%))	25 (75.8%)
Inclusive Algorithm	8,685 (31.3%)	251 (90.0%)	75 (100%)	30 (90.9%)
Simple	5318 (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 DH					Accuracy of Algorithm at IH
		Routine Surveillance					Routine Surveillance
Algo		SSI	no SSI	Total	Algo		SSI	no SSI	Total
	SSI	6	71	77		SSI	9	704	713
	no SSI	7	1345	1352		no SSI	16	10857	10873
	Total	13	1416	1429		Total	25	11561	11586

	Sensitivity			46.2%		Sensitivity			36.0%
	Specificity			95.0%		Specificity			93.7%
	Positive Predictive Value			7.8%		Positive Predictive Value			1.3%
	Negative Predictive Value			99.5%		Negative Predictive Value			99.9%
Accuracy of Algorithm at VA SLCHCS					Accuracy of Algorithm at VVMC
		Routine Surveillance					Routine Surveillance
Algo		SSI	no SSI	Total	Algo		SSI	no SSI	Total
	SSI	2	33	35		SSI	0	17	17
	no SSI	2	531	533		no SSI	3	832	835
	Total	4	564	568		Total	3	849	852

	Sensitivity			50.0%		Sensitivity			0.0%
	Specificity			94.1%		Specificity			98.0%
	Positive Predictive Value			5.7%		Positive Predictive Value			0.0%
	Negative Predictive Value			99.6%		Negative Predictive Value			99.6%

Abbreviations: SSI = surgical site infection; Algo, algorithm

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

	DH			IH			VA SLCHCS			VVMC
	TP	FN	SN (%)	TP	FN	SN (%)	TP	FN	SN (%)	TP	FN	SN (%)
CABG	NA	NA	NA	4	4	50.0%	0	0	NA	0	0	NA
HERNIA	3	3	50.0%	0	0	NA	1	0	100.0%	0	1	0.0%
HIP	1	3	25.0%	3	5	37.5%	0	2	0.0%	0	1	0.0%
KNEE	2	1	66.7%	2	7	22.2%	1	0	100.0%	0	1	0.0%
Total	6	7	46.2	4	4	50.0	2	2	50.0	0	3	0.0

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 DH					Accuracy of Adjudication at IH
		Routine Surveillance					Routine Surveillance
Adjudicated		SSI	no SSI	Total	Adjudicated		SSI	no SSI	Total
	SSI	6	1.42	7.42		SSI	9	0	713
	no SSI	3	1410	1348		no SSI	16	11559	11575
	Total	9	1411.4	1420.4		Total	25	11559	11584

	Sensitivity			66.7%		Sensitivity			36.0%
	Specificity			99.9%		Specificity			100.0%
	Positive Predictive Value			80.9%		Positive Predictive Value			100.0%
	Negative Predictive Value			99.8%		Negative Predictive Value			99.9%
Accuracy of Adjudication at VA SLCHCS					Accuracy of Adjudication at VVMC
		Routine Surveillance					Routine Surveillance
Adjudicated		SSI	no SSI	Total	Adjudicated		No Change
	SSI	2	4	35
	no SSI	2	560	562
	Total	4	564	568

	Sensitivity			50.0%
	Specificity			99.3%
	Positive Predictive Value			33.37%
	Negative Predictive Value			99.6%

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

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Current as of December 2012

Internet Citation: ssiapvtables.htm. December 2012. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/research/findings/final-reports/ssi/ssiapvtables.html