Costs of surgical site infections that appear after hospital discharge.Data were collected from surgical patients in the hospital and on 4 occasions postdischarge. The incidence of postdischarge surgical site infection was 8.46%. Strong evidence showed that these infections caused minor additional costs, which contradicts existing literature. We discuss why previous studies might have overstated o·ver·state
tr.v. o·ver·stat·ed, o·ver·stat·ing, o·ver·states
To state in exaggerated terms. See Synonyms at exaggerate.
Most cases of healthcare-acquired surgical site infections (SSI (1) See server-side include and single-system image.
(2) (Small-Scale Integration) Less than 100 transistors on a chip. See MSI, LSI, VLSI and ULSI.
1. (electronics) SSI - small scale integration.
2. ) appear after discharge from hospital (1); rates of postdischarge SSI between 2% and 14% have been reported (2). Little is known of the costs of postdischarge SSI, but 2 studies suggest that they are large (3-5) with health services health services Managed care The benefits covered under a health contract and patients incurring costs and subsequent production losses. The combination of high frequency and high cost suggests that programs that reduce the risks of postdischarge SSI should be adopted, but decision makers should assess the cost-effectiveness of additional prevention efforts. This exercise requires valid estimates of the change in costs and benefits from additional prevention programs (6, 7). Understanding the costs of postdischarge SSI is therefore essential. The work completed so far is valuable but demonstrates some methodologic weaknesses. Plowman et al. (3,4) assessed only patient-reported signs and symptoms of postdischarge SSI, and Perencevich et al. (5) relied on routine healthcare records for diagnosis/surveillance and matched case patients with controls on only 3 confounding variables A confounding variable (also confounding factor, lurking variable, a confound, or confounder) is an extraneous variable in a statistical or research model that should have been experimentally controlled, but was not. .
Our study assessed the costs of postdischarge SSI. We adopted a societal perspective and included the costs incurred by healthcare services, private costs, and production losses. The research method was chosen to address the suggested weaknesses of the studies of Plowman et al. (3,4) and Perencevich et al. (5).
We recruited, in consecutive order, adults (>18 years of age) admitted to 3 Australian hospitals in 2004 for knee or hip prostheses Prostheses
A synthetic object that resembles a missing anatomical part.
Mentioned in: Microphthalmia and Anophthalmia , cardiovascular procedures, femoropopliteal bypass grafts bypass graft Surgery A surrogate blood vessel used to reroute blood; BGs may be synthetic–Dacron, or autologous–vein from the Pt's own leg, to substitute for diseased vessel , or abdominal procedures, including abdominal hysterectomies abdominal hysterectomy
A hysterectomy made through an incision in the abdominal wall. Also called abdominohysterectomy.
abdominal hysterectomy and lower segment caesarean sections caesarean section: see cesarean section. . Four infection-control research nurses recruited participants and collected data during the hospital admission process and on 4 separate occasions after surgery by visiting the patients in their homes (data collection is illustrated in the Figure). Monetary estimates of all costs were made by multiplying frequency with a cost vector for the item of service (9-12). Production losses were estimated by comparing the presurgery level of (unwaged unwaged
(of a person) not having a paid job and waged) productive activity with the actual level of (unwaged and waged) productive activity achieved during the 4 weeks postdischarge. These losses were converted to a monetary value by using market prices for labor, approximated by average pretax pre·tax
Existing before tax deductions: pretax income.
pretax adj [profit] → vor (Abzug der) Steuern earnings (13).
The question we address is whether postdischarge SSIs independently affect costs. The specific cost outcomes we seek to explain are listed in online Appendix 1 (available from http://www.cdc.gov/ncidod/EID/vol 12no05/05-1321 _appl.htm). Adjustment was made for other factors believed to influence these cost outcomes (i.e., confounding confounding
when the effects of two, or more, processes on results cannot be separated, the results are said to be confounded, a cause of bias in disease studies.
confounding factor factors); these included the type of surgical procedure, duration of surgery, American Society of Anesthesiologists The American Society of Anesthesiologists (ASA) is an association of physicians (primarily anesthesiologists) whose stated goal is to raise and maintain the standards of the medical practice of anesthesiology and improve the care of the patient. score, wound class, number of coexisting co·ex·ist
intr.v. co·ex·ist·ed, co·ex·ist·ing, co·ex·ists
1. To exist together, at the same time, or in the same place.
2. conditions, length of hospital stay, whether patient was funded by the public sector or private insurance, admitting hospital, sex, age, ethnicity, patient's socioeconomic status socioeconomic status,
n the position of an individual on a socio-economic scale that measures such factors as education, income, type of occupation, place of residence, and in some populations, ethnicity and religion. (14), whether the patient was in waged employment, salary level and health-related quality of life as measured by the SF-12v2 Health Survey (available from http://www.sf-36.org/ tools/sf12.shtml) scores at baseline and 4 weeks postdischarge. The complete set of explanatory variables available for analyses and the summary statistics are presented in Table 1 and online Appendix 2 (available at http:// www.cdc.gov/ncidod/EID/vol12no05/05-1321_app2 .htm). Because the outcome variables were continuous and linear, ordinary least squares regression was chosen to model the independent effect of SSI on cost outcomes (Table 2). See online Appendix 3 (available at http://www. cdc.gov/ncidod/EID/vol12no05/05-1321_app3.htm) for a description of the statistical analyses.
The mean age of the 449 patients included in the analyses was 63.65 years (SD 14.34), and 50.56% were women. The mean length of hospital stay for the sample was 7.8 days (SD 8.68, median 6 days, interquartile range In descriptive statistics, the interquartile range (IQR), also called the midspread, middle fifty and middle of the #s, is a measure of statistical dispersion, being equal to the difference between the third and first quartiles. 4-8). Thirty-eight of the 449 patients included in the study had a diagnosis of SSI postdischarge, which indicates an incidence of 8.46% for the 8-month period during which patients were recruited. A higher proportion of persons with SSI (18.24%) compared to those without SSI (2.43%) were readmitted to the hospital, but the mean lengths of stay of the readmitted persons were similar, 16.57 days versus 15.72 days, respectively. Summary statistics for all variables are included in Table 1 and in online Appendix 2, and the ICD-10 procedures for the 38 cases of SSI are described in online Appendix 4 (available at http://www. cdc.gov/ncidod/EID/vol12no05/05-1321_app4.htm).
No evidence was found of multicollinearity or interactions between variables. However, none of the outcome variables were normally distributed, and variance of the error term was not constant (i.e., heteroscedastic), so all models were estimated by using the Huber--White covariance matrix In statistics and probability theory, the covariance matrix is a matrix of covariances between elements of a vector. It is the natural generalization to higher dimensions of the concept of the variance of a scalar-valued random variable. (15). Results of the ordinary least squares regressions are summarized in online Appendix 1. Strong statistical evidence shows that postdischarge SSI independently causes the following: 1.36 extra contacts with community-based services with increased costs of $47.78; 6.46 days of additional antimicrobial antimicrobial /an·ti·mi·cro·bi·al/ (-mi-kro´be-al)
1. killing microorganisms or suppressing their multiplication or growth.
2. an agent with such effects. drug therapy with increased costs of $14.44; and an increase in total health service costs of AU $74 (US $57) when the costs of readmission readmission Managed care The admission of a Pt to a health care facility for a condition–eg, stroke, MI, GI bleeding, hip fracture, cancer surgery, shortly after discharge. See nth admission. Cf Admission, Discharge. to the hospital are excluded and AU $123 (US $94) when the costs of readmission to the hospital are included. The strength of the relationship between SSI and all other cost outcomes was not significant with the 95% confidence interval confidence interval,
n a statistical device used to determine the range within which an acceptable datum would fall. Confidence intervals are usually expressed in percentages, typically 95% or 99%. crossing zero for all other models.
These results support the view that most SSIs first appear after discharge from hospital, but we did not find any evidence that postdischarge SSI causes substantial economic costs even when costs are viewed from a societal perspective. These findings contradict con·tra·dict
v. con·tra·dict·ed, con·tra·dict·ing, con·tra·dicts
1. To assert or express the opposite of (a statement).
2. To deny the statement of. See Synonyms at deny. Perencevich et al. (5), who found the economic cost of a case of SSI diagnosed after discharge was almost 50-fold the estimate we report here. Thus, what might explain this extreme discrepancy in attributed costs? The study designs and research methods differed. Compared to Perencevich et al. (5), we used more control variables (described in Tables 1 and Online Appendix 2 and listed below the table in Appendix 1). Might this extended set of control variables reduce bias from omitted variables and so reduce the cost attributed to SSI? Another factor might be the surveillance method. Perencevich et al. (5) used automated record screening that relied on accurate documentation of diagnostic, testing, or treatment codes and pharmacy records Pharmacy Records is an independent record label based in Melbourne, Australia, and run by Richard Andrew of Registered Nurse.
Pharmacy Records is distributed through MGM Distribution in Australia and through Narwhal Records in the UK. . This process resulted in 89 diagnoses among 4,571 patients, an incidence rate of 1.9%. For our study, patients were recruited before surgery and infection-control research-nurses visited the patients in their homes on 4 occasions after discharge, during which time the wound was examined and the definition of the Centers for Disease Control and Prevention Centers for Disease Control and Prevention (CDC), agency of the U.S. Public Health Service since 1973, with headquarters in Atlanta; it was established in 1946 as the Communicable Disease Center. definition, modified by the Australian Infection Control Association Inc., was applied (8). This method yielded a much higher infection rate of 8.38%. One interpretation is that the surveillance method used by Perencevich et al. was not sensitive to all cases of postdischarge SSI. Instead, only those that generated certain data items in the downstream electronic records were flagged, and these may have been the most serious cases of SSI that generated the greatest costs. This theory might be supported by the higher rate of readmission among the patients with cases of SSI in the Perencevich data (34%) compared to the rate in our study (18%).
Of course, other factors may have an influence, such as the case mix and socioeconomic characteristics of the participants, the costs of the inputs to healthcare services (i.e., salaries for doctors and nurses), consumer preferences (i.e., for more or less postdischarge care), and predefined care protocols.
Also, our data only describe a 4-week period after surgery and not the 8-week period considered by Perencevich et al. (5). We recommend that readers interpret our results carefully but nevertheless suggest that the economic costs of SSIs that occur after hospital discharge are real but not substantial.
The Centre for Healthcare Related Infection Surveillance and Prevention, Queensland Health, provided funding to the Queensland University of Technology for the development and publication of this research.
Dr Graves is a senior research fellow in health economics with a joint appointment in the School of Public Health, Queensland University of Technology, and the Centre for Healthcare Related Infection Control and Surveillance, Princess Alexandra Hospital The Princess Alexandra Hospital (PAH), is located on Ipswich Road in Woolloongabba, Australia. It is one of the major hospitals in Brisbane and is a teaching hospital of the University of Queensland. , Brisbane. His research interests include all aspects of the economics of hospital infection and other chronic and infectious diseases infectious diseases: see communicable diseases. .
(1.) Holtz TH, Wenzel RP. Postdischarge surveillance for nosocomial nosocomial /noso·co·mi·al/ (nos?o-ko´me-il) pertaining to or originating in a hospital.
1. Of or relating to a hospital.
2. wound infection. A brief review and commentary. Am J Infect infect /in·fect/ (in-fekt´)
1. to invade and produce infection in.
2. to transmit a pathogen or disease to.
1. Control. 1992;20:206-13.
(2.) Kent P, McDonald M, Harris O, Mason T, Spelman D. Post-discharge surgical wound infection surveillance in. A provincial hospital: follow-up rates, validity of data and review of the literature. ANZ ANZ Australia and New Zealand
ANZ Australia and New Zealand Banking Group Limited
ANZ Air New Zealand (NZ national airline) J Surg. 2001;71:583-9.
(3.) Plowman RP, Graves N, Griffin M, Roberts JA, Swan AV, Cookson BC, et al., The socioeconomic burden of hospital acquired infection. London: Public Health Laboratory Service; 1999.
(4.) Plowman RP, Graves N, Griffin MAS, Roberts JA, Swan AV, Cookson B, et al. The rate and cost of hospital-acquired infections Hospital-Acquired Infections Definition
A hospital-acquired infection is usually one that first appears three days after a patient is admitted to a hospital or other health care facility. occurring in patients admitted to selected specialties of a district general hospital in England and the national burden imposed. J Hosp Infect. 2001;47:198-209.
(5.) Perencevich EN, Sands KE, Cosgrove SE, Guadagnoli E, Meara E, Platt R. Health and economic impact of surgical site infections diagnosed after hospital discharge. Emerg Infect Dis. 2003;9:196-203.
(6.) Graves N, Halton K, Lairson D. Economics and preventing hospital-acquired infection broadening the perspective. Infect Control Hosp Epidemiol. In press.
(7.) Graves N. Economics and preventing hospital-acquired infection. Emerg Infect Dis. 2004; 10:561-6.
(8.) Aurich E, Borgert J, Butler M, Cadwallader H, Collignon P, Eades M, et al. Introduction to Australian surveillance definitions: surgical site infections and bloodstream blood·stream
The flow of blood through the circulatory system of an organism.
the blood flowing through the circulatory system in the living body. infections. Australian Infection Control. 2000;5:25-31.
(9.) The Australian Government, Department of Health and Ageing Health and Ageing is a research programme set up by the Geneva Association, also known as the International Association for the Study of Insurance Economics. The Geneva Association Research Programme on Health and Ageing seeks to bring together facts, figures and analyses . Manual of resource items and their associated costs for use in submissions to the Pharmaceutical Benefits Advisory Committee involving economic evaluation [cited 2005 Mar] (available from http://www.health.gov.au/internet/wcms/publishing.nsf/Content/ healthpbs-general-pubs-manual-content.htm, ed). Canberra, Australia: Department of Health and Ageing; 2004.
(10.) MIMS MIMS Music Is My Savior (music album)
MIMS Medical Information Management System
MIMS Multimedia Integrated Modeling System (US EPA)
MIMS Membrane Introduction Mass Spectrometry online [cited March 2005]. Available from http://www. mims.hcn.net.au/ifmx-nsapi/mims-data/?MIval=2MIMS_ssearch#
(11.) Australian Institute of Health and Welfare. Australian hospital statistics 2001-2002. Canberra, Australia: Australian Institute of Health and Welfare; 2003.
(12.) The Australian Government, Department of Health and Ageing. Medicare benefits schedule book. Canberra, Australia: Department of Health and Ageing; 2004.
(13.) Australian Bureau of Statistics The Australian Bureau of Statistics (ABS) is the Australian government agency that collects and publishes statistical information about Australia and its people. Population and Housing
The agency undertakes the Australian Census of Population and Housing. . Average weekly earnings. Canberra, Australia: Australian Bureau of Statistics; 2004.
(14.) Jones FL, McMillan J. Scoring occupational categories for social research: a review of current practice with Australian examples. Work, Employment and Society. 2001;15:539-63.
(15.) White H. A heteroscedasticity-consistent covariance matrix estimator and a direct test for heteroscedasticity. Econometrica. 1980;48:817-38.
Nicholas Graves,* [dagger] Kate Halton,* [dagger] Merrilyn Curtis,* Shane Doidge,* David Lairson, [double dagger double dagger
A reference mark () used in printing and writing. Also called diesis.
Noun 1. ] Marylou McLaws, [section] and Michael Whitby*
* The Centre for Healthcare Related Infection Surveillance and Prevention, Brisbane, Queensland, Australia; [dagger] Queensland University of Technology, Brisbane, Queensland, Australia; [double dagger] University of Texas Health Science Center at Houston, Houston, Texas “Houston” redirects here. For other uses, see Houston (disambiguation).
Houston (pronounced /'hjuːstən/) is the largest city in the state of Texas and the , USA; and [section] University of New South Wales The University of New South Wales, also known as UNSW or colloquially as New South, is a university situated in Kensington, a suburb in Sydney, New South Wales, Australia. , Sydney, New South Wales New South Wales, state (1991 pop. 5,164,549), 309,443 sq mi (801,457 sq km), SE Australia. It is bounded on the E by the Pacific Ocean. Sydney is the capital. The other principal urban centers are Newcastle, Wagga Wagga, Lismore, Wollongong, and Broken Hill. , Australia
Address for correspondence: Nicholas Graves, School of Public Health, Queensland University of Technology, Victoria Park Rd, Kelvin Grove Kelvin Grove is the name of various places:
Table 1. Demographic characteristics of included patients by surgical site infection (SSI) % (no.) Characteristic No SSI SSI (n = 38) (n = 411) Age, y, mean (SD) 63.58 (14.41) 64.37 (13.72) Socioeconomic score (1-100),* mean (SD) 35.67 (19.17) 40.37 (20.53) Male 48.66 (199) 57.89 (22) Recruiting hospital 280-bed district hospital 35.04 (144) 47.37 (18) 712-bed teaching hospital 47.45 (195) 36.84 (14) 156-bed district hospital 16.79 (69) 15.79 (6) Income Currently in waged employment 20.68 (85) 31.58 (12) [less than or equal to] $50,000/y 12.41 (51) 23.68 (9) >$50,000/y 2.68 (11) 5.26 (2) Refused to answer 5.35 (22) 2.63 (l) Education Left school at <15 y 60.83 (250) 63.16 (24) Left school at 16-18 y 7.54 (31) 13.16 (5) Some form of higher education 30.41 (125) 23.68 (9) Ethnicity Caucasian 96.11 (395) 97.37 (37) Aboriginal 0.24 (l) 0.00 (0) Asian 0.24 (1) 0.00 (0) Other 2.43 (0) 2.63 (l) How patient was funded Public 91.97 (395) 94.74 (36) Intermediate 6.81 (28) 5.26 (2) Private 0.24 (l) 0.00 (0) * See Jones and McMillan (14) for the scoring algorithm used. Table 2. Cost outcomes * Mean (SD) Outcome No SSI, n = 411 SSI, n = 38 Healthcare services No. contacts with hospital-based services in 4 wk PD 1.10(l.68) 1.11 (1.43) Cost of contacts with hospital-based services in 4 wk PD ($) 40 (60) 40 (52) No. contacts with community-based services in 4 wk PD 1.85 (2.72) 3.13 (3.04) Cost of contacts with community-based services in 4 wk PD ($) 62 (103) 105 (111) No. tests/swabs 0.48 (l.43) 0.71 (1.27) Costs of tests/swabs ($) 11 (35) 16 (28) No. of days on antimicrobial drugs during 4 wk PD 0.96 (3.10) 6.76 (8.23) Costs of antimicrobial drugs 2.16 (9.08) 14.47 (19.96) Sum of all costs incurred by health care services, excluding costs of readmission ($) 115 (128) 176 (144) Sum of all costs incurred by health care services, including costs of readmission ($) 417 (3050) 2,361 (8,811) Production losses Patient production losses during 4 wk PD (min) 5,237 (5,488) 7,295 (6,349) Monetary valuation of patient production losses ($) 1,895 (1,986) 2,640 (2,298) Informal care givers production losses during 4 wk PD 1,630 (2,329) 2,863 (3,168) Monetary valuation of Informal care giver production losses ($) 590 (843) 1,036 (1,146) Private costs Time patient spent accessing hospital services (min) 169 (444) 184 (338) Time patient spent accessing community-based services (min) 129 (410) 282.76 (528.14) Total out-of-pocket expenditures during 4 wk PD ($) 5 (19) 4 (21) SF-12 Physical Component Summary (enrollment) 39.15 (11.76) 37.63 (12.24) SF-12 Mental Component Summary (enrollment) 50.37 (10.06) 48.87 (10.60) SF-12 Physical Component Summary (wk 4) 39.03 (8.84) 37.68 (8.04) SF-12 Mental Component Summary (wk 4) 53.92 (8.35) 52.06 (11.10) * SSI, surgical site infection; PD, postdischarge; min, minutes of time.