Table 2.

Methodologic characteristics of studies of economic burden of patient safety events in acute care (n = 61)

Methodologic feature	Studies with this feature present % (n)	Example of information used in the analysis
Study design
The research question is stated	100% (61)	“The aim of this study was to evaluate the epidemiology, additional length of stay, incremental costs and outcomes due to hospitalacquired infections, and to estimate the potential impact of infection control on community hospitals and medical centers.”26
The economic importance of the research question is stated	100% (61)	“More recently, an argument has been made to focus on direct costs (primarily consumables), because they are most subject to savings by implementation of effective infection control interventions.”37
The viewpoint(s) of the analysis are clearly stated and justified	100% (61)	“The main focus of costs calculated in this study was the health care sector.”13
The form of economic evaluation used is stated	67% (41)	“Economic burden of surgical site infections at a European university hospital.”32
The choice of form of economic evaluation is justified in relation to the questions addressed	67% (41)	“To quantify the economic and medical burden of SSIs in a European university hospital, we conducted a matched casecontrol study nested in a larger prospective observational study.”32
Data collection
The primary outcome measure(s) for the economic evaluation are clearly stated	74% (45)	“Data on the predicted number of cases of hospital-acquired infection were combined with data on the estimated prolongation of stay due to hospital-acquired infection. This produced an estimate of the number of bed days attributable to hospital-acquired infection. Valuations of the opportunity cost of the resources used to supply a bed day were applied to derive a monetary estimate of the opportunity cost of hospital-acquired infection.”30
Productivity changes (if included) are reported separately	11% (7)	“Lost productivity costs due to hospital staff members on sick leave totaled €9,264.”58
The relevance of productivity changes to the study question is discussed	15% (9)	“Additional expenses were €18,375 for increased nursing care (extra staffing of temporary isolation ward).”58
Quantities of resources are reported separately from their unit costs	72% (44)	“All patients staying more than 24 hours in a 19-bed MICU at Barnes-Jewish Hospital from Jul 1, 1997 to Dec 31, 1999 were eligible. All health care workers and visitors were required to wear gowns and gloves on entry into the rooms of patients colonized or infected with VRE from Jul 1, 1997 to Jun 30, 1998 and from Jul 1, 1999 to Dec 31, 1999. All patients were actively screened[…]. A matched cohort study design was used to determine the attributable cost of VRE. Patients without VRE from the same [medical intensive care unit] population were matched to patients with VRE by diagnosis-related group (DRG) code, APACHE score, and age.VRE-attributable length of MICU stay (d): 4.0, 18.9, 35.3 VRE-attributable LOS (d): 8.3, 38.2, 18.9.”67
Methods of the estimation of quantities and unit costs are described	88% (54)	“Overall costs for the vancomycin-resistant Enteroccoci surveillance and infection control program were estimated using the hospital’s step-down cost allocation system, which recorded line-item cost data per resource consumed and total cost per hospital admission. MICU costs were estimated from these data by dividing the patient’s total hospitalization cost by total days of hospitalization and then multiplying the quotient by the patient’s total MICU-days. This data system also provided hospital reimbursement data, type of insurance, case-mix index, and DRG. Variable cost – gown $0.75 each – gloves $0.07/pair – hand hygiene $0.10/use – nursing time $27/hour – isolation cart set up $18.00 – V RE-negative $12.13 – V RE-positive $24.29”67
Currency and price data are recorded	80% (49)	“Costs are reported in 2001 Euros (1€ = US $0.95).”46
Details of currency of price adjustments for inflation or currency conversion are given	39% (24)	“All costs were adjusted to 1999 dollars using the consumer price index for health care.”44
Analysis and interpretation of results
Time horizon of costs and benefits is stated	87% (53)	“In the hospital X, a total of 90 persons with symptoms and signs consistent with norovirus gastroenteritis with clinical onsets in the time period from Dec 1, 2006 to Feb 13, 2007 were reported.”58
Details of statistical tests and confidence intervals are given for stochastic data	95% (58)	“Using logistic regression, preoperative antibiotic therapy (cefazolin/metronidazole vs cefotetan), patient demographics, surgical procedure, obesity, and modified SECNIC score were examined as predictors of LOS ≥ 1 week and cost ≥$15,000.”34
The approach to sensitivity analysis is given	30% (18)	“Models 2 and 3 incorporated additional cost predictors sequentially: suspected and confirmed HAI and ICU treatment.”23
The choice variables for sensitivity analysis is justified	30% (18)	“Several parameters were changed to determine the impact of our four main assumptions on the net benefits of gowns.”67
The ranges over which the variables are varied are stated	31% (19)	“The variation between 60 to 140 patient contacts yielded net benefits of $388,664 and $450,017, respectively. The variable of 1 to 4 cultures per patients resulted in net benefits of $418,188 and $421,464, respectively. The variation in costs of labor and materials results in net benefits of $406,488 and $435,426, respectively.”67
Major outcomes are presented in a disaggregated as well as aggregated forma	54% (33)	“Cost data were available for all of the 164 patients admitted after Jul 1, 1999.”45
The answer to the study question is given	98% (60)	“In conclusion, in the presence of prompt catheter removal and initiation of antimicrobial therapy, no significant attributable mortality could be documented in critically ill patients. However, increases in the durations of ICU and hospital stay contribute to an important economic burden. These significant increases in cost underscore the need to vigorous application of evidence-based cost-effective preventive measures.”38
Conclusions follow from the data reported	98% (60)	“Prevention of MRSA infection is essential if we are to minimize its major impact on individual patients and if we are to get the most effective use of health care resources.”64
Conclusions are accompanied by the appropriate caveats	93% (57)	“It should be understood that the cost of an infection, if avoided, will not be realized as a cash saving. Many of the costs/benefits are fixed and it is principally the variable costs/benefits (for example drugs and other consumables), which represent a small proportion of the total costs, that would show as cash savings, and as such an expenditure that could be avoided.”27

Notes:

^aWhen the major outcomes are presented in aggregated form the overall cost is stated, for example, surgical site infections cost $10,000. If the major outcomes are presented in disaggregated form the different components that make up the overall cost is stated. For example, surgical site infections cost $10,000, of that professional costs were $3000, medication costs were $2000 and hospitalization costs were $5000. (Numbers used are for illustration only).

Abbreviations: LOS, length of stay; MRSA, methicillin-resistant Staphylococcus aureus; VRE, vancomycin-resistant Enterococcus.