Appendix B. Database Analysis

Proactive Risk Assessment of Surgical Site Infection in Ambulatory Surgery Centers

AHRQ's Healthcare Cost and Utilization Project (HCUP) State Ambulatory Surgery Database (SASD) databases were analyzed to identify the most common surgeries, the demographic profile of individuals receiving them, and the institutional profile of locations in which they are performed. Specifically, the 2006-2008 SASD databases for Maryland, New Jersey, and California were used in this study. Because the SASD database for California had data on both hospital-based and free-standing ASCs and included many variables that were of interest to this study, we analyzed the SASD California 2008 database extensively.1 We then extended this analysis to years 2006 and 2007, which produced results similar to those for 2008. This analysis resulted in a list of the top ten procedures for hospital-based and free-standing ASCs. We then analyzed the distribution of these procedures for hospital-based ASCs by the type of ownership (i.e., for-profit or not-for-profit) and by demographic characteristics. We repeated the same analysis for the top five surgical procedures requiring an incision for both hospital-based and free-standing ASCs.

In the California 2008 SASD, the total number of participating outpatient surgery centers was 831. There were 368 (44.28%) outpatient surgery centers that were hospital-based facilities and 463 (55.72%) that were free-standing facilities. The total number of records (including those records with some variables missing) was 2,852,294. Of these, 64.7% of the records were from hospital-based centers, while 35.3% of the records were from free-standing ASCs. More than 200 types of procedures were recorded as the patient's primary procedure in the database. Colonoscopy and biopsy, lens and cataract procedures, and upper gastrointestinal endoscopy and biopsy were the three most common primary procedures. In total, 35.04% of all the patients recorded them as their primary procedures. For pediatric patients, tonsillectomy and/or adenoidectomy, myringotomy, and oral and dental services were the three most common procedures, whereas for adult patients, colonoscopy and biopsy, insertion of catheter or spinal stimulator and injection into spinal cana, and lens and cataract procedures were the three most common procedures. Figures 1 and 2 present the top 10 procedures for hospital-based and free-standing outpatient surgery centers, respectively.

In California 2008 SASD, there were 65 (18.11%) government, non-federal outpatient surgery centers, 216 (60.17%) non-government not-for-profit centers, and 78 (21.73%) investor-owned for-profit ASCs. Among 1,818,577 records from hospital-based outpatient surgery centers, 14.29% of the records were from government, non-federal centers, 71.9% of the records were from non-government not-for-profit facilities, and 14.3% records were from investor-owned for-profit ASCs. Table 1 presents the frequency and percent distribution for top 10 procedures by ownership for hospital-based outpatient surgery centers only.

Table 1. Frequency and Percent Distribution for Top 10 Procedures for Hospital-Based Outpatient Surgery Centers Only (California 2008 SASD)

Government, Non Federal
Non-Government Not-For-Profit
Investor-Owned, For-Profit
CPT ProceduresFreq%CPT ProceduresFreq%CPT ProceduresFreq%
Colonoscopy and biopsy36,21513.93%Colonoscopy and biopsy175,81713.44%Colonoscopy and biopsy31,90812.75%
Upper gastrointest. endoscopy, biopsy20,6617.95%Lens and cataract procedures90,2746.90%Upper gastrointest. endoscopy, biopsy17,4746.98%
Lens and cataract procedures17,4966.73%Upper gastrointest. endoscopy, biopsy82,9686.34%Insertion of catheter or spinal stimulator; injection into spinal canal13,6175.44%
Insertion of catheter or spinal stimulator; injection into spinal canal11,0594.25%Diagnostic cardiac catheterization, coronary arteriography31,8562.43%Lens and cataract procedures13,1185.24%
Excision of skin lesion5,3572.06%Insertion of catheter or spinal stimulator; injection into spinal canal31,8052.43%Excision of semilunar cartilage of knee5,8852.35%

In all, 29.1% of all the patients have a procedure with incision recorded as their primary procedures. Table 2 and Figure 3 display the frequency and percent distribution for top five surgical procedures with incision only.

Table 2.Frequency and Percent Distribution for Top 5 Surgical Procedures with Incision Only (California 2008 SASD)

Surgical proceduresTotalHospital-basedFreestanding
Lens and cataract procedures249,1348.73%121,7166.60%127,41812.65%
Excision of semilunar cartilage of knee67,7422.38%38,0742.06%29,6682.95%
Other therapeutic procedures on muscles and tendons65,7732.31%39,8302.16%25,9432.58%
Inguinal and femoral hernia repair48,6741.71%40,7902.21%7,8840.78%
Other OR therapeutic procedures on joints46,8851.64%26,5581.44%20,3272.02%

Finally, the demographic data of patients with arthroscopic procedure (CPT code 29866-29889) in the California 2008 SASD dataset is presented in Table 3.

Table 3. Demographic Data of Patients Having Arthroscopic Procedures (California 2008 SASD)

Demographic FactorTotalHospital-Based CenterFree-standing Center
< 1 month00.00%00.00%00.00%
1-11 months (0)20.00%10.00%10.00%
12-59 months (1-4 years)30.00%20.00%10.00%
60 months to <12 years
(5-11 years)
12 years to < 18 years4,8755.27%3,2486.13%1,6274.11%
18-44 years29,34431.70%17,29232.63%12,05230.44%
45-64 years44,80748.40%24,84946.90%19,95850.41%
65-84 years12,28213.27%6,77912.79%5,50313.90%
>85 years3260.35%2120.40%1140.29%
Private insurance64,69466.98%38,11569.57%26,57963.60%
Patient Residence
Metro - 1 million population+67,89570.36%37,52168.56%30,37472.73%
Metro - 250,000 to 1 million population18,68619.37%11,29020.63%7,39617.71%
Metro - fewer than 250,000 population6,4186.65%3,3656.15%3,0537.31%
Non-Metro - Urban population of 20,000 +, adjacent to a metro area1,4751.53%1,0351.89%4401.05%
Non-Metro - Urban population of 20,000 +, not adjacent to a metro area4390.45%4170.76%220.05%
Non-Metro - Urban population of 2,500 - 19,999, adjacent to a metro area7850.81%4870.89%2980.71%
Non-Metro - Urban population of 2,500 - 19,999, not adjacent to a metro area6360.66%5471.00%890.21%
Non-Metro - Completely rural or <2,500 urban population, adjacent to a metro area1510.16%660.12%850.20%
Non-Metro - Completely rural or <2,500 urban population, not adjacent to a metro area50.01%00.00%50.01%
Asian or Pacific Islander1,7682.92%1,2823.27%4862.29%
Native American440.07%250.06%190.09%

1 Note that the New Jersey SASD database did not contain data on free-standing ASCs, whereas both the Maryland and California SASD databases did. However, the California SASD database included more variables that were of interest to this study and also included many more records than the Maryland database.

Page last reviewed April 2013
Internet Citation: Appendix B. Database Analysis: Proactive Risk Assessment of Surgical Site Infection in Ambulatory Surgery Centers. April 2013. Agency for Healthcare Research and Quality, Rockville, MD.