Use of the appropriateness evaluation protocol for estimating the incremental costs associated with nosocomial infections

Hospital Admission Due to Hypotension in Australia and in England and Wales

OBJECTIVES

Hypotension is overlooked because it is often harmless, easily reversed, and can have few or even no symptoms. However, complications of untreated hypotension are dangerous and can result in death. The aim of this study was to examine the trend of hospital admission due to hypotension in Australia and in England and Wales between 1999 and 2020.

METHOD

This was a secular trend analysis study that examined the hospitalisation pattern for hypotension in Australia, England, and Wales between 1999 and 2020. Hospitalisation data were obtained from the National Hospital Morbidity Database in Australia, Hospital Episode Statistics database in England, and Patient Episode Database for Wales. We analysed the variation in hospitalisation rates using the Pearson chi-square test for independence.

RESULTS

Our study showed that hypotension hospital admission rates increased significantly between 1999 and 2020 by 168%, 398%, and 149% in Australia, England, and Wales, respectively. The most common hypotension hospital admissions reason was orthostatic hypotension. All types of hypotension-related hospital admissions in Australia, England, and Wales were directly related to age, more common among the age group 75 years and above. Bed-days hypotension hospital admission patients accounted for 84.6%, 99.5%, and 99.7% of the total number of hypotension hospital admissions in Australia, England, and Wales.

CONCLUSION

In the past two decades, orthostatic hypotension was the most prevalent type of hypotension that required hospitalization in Australia, England, and Wales. Age was identified as the primary risk factor for hypotension across all causes. Future research should focus on identifying modifiable risk factors for hypotension and developing strategies to reduce the burden of orthostatic hypotension.

Evaluation of the costing methodology of published studies estimating costs of surgical site infections: A systematic review

OBJECTIVES

Surgical site infections (SSIs) are associated with increased length of hospitalization and costs. Epidemiologists and infection control practitioners, who are in charge of implementing infection control measures, have to assess the quality and relevance of the published SSI cost estimates before using them to support their decisions. In this review, we aimed to determine the distribution and trend of analytical methodologies used to estimate cost of SSIs, to evaluate the quality of costing methods and the transparency of cost estimates, and to assess whether researchers were more inclined to use transferable studies.

METHODS

We searched MEDLINE to identify published studies that estimated costs of SSIs from 2007 to March 2021, determined the analytical methodologies, and evaluated transferability of studies based on 2 evaluation axes. We compared the number of citations by transferability axes.

RESULTS

We included 70 studies in our review. Matching and regression analysis represented 83% of analytical methodologies used without change over time. Most studies adopted a hospital perspective, included inpatient costs, and excluded postdischarge costs (borne by patients, caregivers, and community health services). Few studies had high transferability. Studies with high transferability levels were more likely to be cited.

CONCLUSIONS

Most of the studies used methodologies that control for confounding factors to minimize bias. After the article by Fukuda et al, there was no significant improvement in the transferability of published studies; however, transferable studies became more likely to be cited, indicating increased awareness about fundamentals in costing methodologies.

The increasing impact of length of stay "outliers" on length of stay at an urban academic hospital

BACKGROUND

As healthcare systems strive for efficiency, hospital "length of stay outliers" have the potential to significantly impact a hospital's overall utilization. There is a tendency to exclude such "outlier" stays in local quality improvement and data reporting due to their assumed rare occurrence and disproportionate ability to skew mean and other summary data. This study sought to assess the influence of length of stay (LOS) outliers on inpatient length of stay and hospital capacity over a 5-year period at a large urban academic medical center.

METHODS

From January 2014 through December 2019, 169,645 consecutive inpatient cases were analyzed and assigned an expected LOS based on national academic center benchmarks. Cases in the top 1% of national sample LOS by diagnosis were flagged as length of stay outliers.

RESULTS

From 2014 to 2019, mean outlier LOS increased (40.98 to 45.11 days), as did inpatient LOS with outliers excluded (5.63 to 6.19 days). Outlier cases increased both in number (from 297 to 412) and as a percent of total discharges (0.98 to 1.56%), and outlier patient days increased from 6.7 to 9.8% of total inpatient plus observation days over the study period.

CONCLUSIONS

Outlier cases utilize a disproportionate and increasing share of hospital resources and available beds. The current tendency to exclude such outlier stays in data reporting due to assumed rare occurrence may need to be revisited. Outlier stays require distinct and targeted interventions to appropriately reduce length of stay to both improve patient care and maintain hospital capacity.

Total and Attributable Costs of Surgical-Wound Infections at a Canadian Tertiary-Care Center

OBJECTIVE: To determine the total and attributable costs of surgical-wound infections in a Canadian teaching hospital.

DESIGN: Retrospective incidence series study with chart review and examination of resource utilization attributable to wound infection. The charts of inpatients with wound infections were examined using the Appropriateness Evaluation Protocol (AEP), a validated chart review instrument designed to determine appropriateness of care, modified for wound infections.

SETTING: A university referral center in Canada.

PATIENTS: Medical records were abstracted from patients with wound infections who underwent an inpatient clean or clean-contaminated procedure during 1991.

MEASUREMENTS: During the wound-infection treatment period, the hospital costs associated with providing care were tabulated for all inpatient days and for outpatient and emergency visits. Costs taken into account included nursing salary and benefits, nonphysician professional services, operating room time, laboratory, pharmacy, supplies, ancillary tests, and hotel costs.

RESULTS: We identified 108 wound infections. Twenty-two patients required 28 surgical procedures related to a wound infection. Inpatient days totalled 1,116, costing $394,337. Fifty-five emergency and 42 clinic visits occurred, costing $27,193. By applying the AEP to the inpatient days, 833 days, or 10.2 days per case, were directly attributable to the wound infection. The hospital costs for inpatient care attributable to wound infections were $321,533 in total, or $3,937 per infection. Costs were distributed as follows: nursing, 51%; hotel, 14%; pharmacy, 10%; laboratory, 9%; emergency and outpatient clinic, 6%; professional services, 5%; operating room, 3%; and ancillary tests, 2%.

CONCLUSIONS: Wound infections contribute markedly to extra days of hospitalization and related costs. The AEP method is applied easily to determine attributable days of care and costs of wound infections, which are necessary to calculate the cost-benefit of infection control programs.

Cost-Effectiveness of Perioperative Mupirocin Nasal Ointment in Cardiothoracic Surgery

Objective:

To assess the cost-effectiveness of perioperative intranasal application of mupirocin calcium ointment in cardiothoracic surgery.

Design:

Cost-effectiveness analysis based on results of an intervention study with historical controls.

Setting:

University Hospital Rotterdam, a tertiary referral center for cardiac and pulmonary surgery.

Patients:

Consecutive patients undergoing cardiothoracic surgery between August 1, 1989, and February 1, 1991 (control group, n=928), and between March 1, 1991, and August 1, 1992 (intervention group, n=868).

Intervention:

Perioperative nasal application of mupirocin calcium ointment started on the day before surgery, continued for 5 days, twice daily.

Results:

Postoperative costs were increased significantly in patients with a surgical-site infection (SSI), compared with uninfected patients (P<.001). Mean SSI-attributable costs were estimated at $16,878 (95% confidence interval, $15,575-$18,181). The incidence of SSIs was 7.3% in the control group and 2.8% in the intervention group, mupirocin effectiveness being 62%. The costs of mupirocin were $11 per patient. Thus, the savings per SSI prevented were $16,633. To validate this comparative estimate of SSI-attributable costs, a noncomparative analysis of the postoperative length of stay (POLS) was performed, according to the Appropriateness Evaluation Protocol. Approximately 50% of the comparative SSI-attributable POLS were judged SSI-attributable in the noncomparative analysis. Sensitivity analyses, testing for the robustness of our conclusions, indicated that the presented model is rather insensitive to variations in the incidence of SSIs and for the effectiveness and costs of mupirocin. SSI-attributable costs were shown to be the only variable with substantial effect on the cost-effectiveness ratio. Perioperative mupirocin would result in net costs instead of savings only if SSI-attributable costs were less than $245.

Conclusions:

SSIs in patients undergoing cardiothoracic surgery are associated with a substantial increase in postoperative costs. Provided that perioperative mupirocin reduces the SSI rate, this measure will be highly cost-effective in most centers providing cardiothoracic surgical services.

Statewide costs of health care-associated infections: estimates for acute care hospitals in North Carolina

BACKGROUND

State-specific, health care-associated infection (HAI) cost estimates have not been calculated to guide Department of Public Health efforts and investments.

METHODS

We completed a cost identification study by conducting a survey of 117 acute care hospitals in NC to collect surveillance data on patient-days, device-days, and surgical procedures during 1 year. We then calculated expected rates and direct hospital costs of surgical site infections (SSI), Clostridium difficile infection, and 3 selected device-related HAIs for hospitals and the entire state using reference data sets such as the National Healthcare Safety Network.

RESULTS

In total, 67 (53%) hospitals responded to the survey. The median bed size of respondent hospitals was 140 (interquartile range, 66-350). A "standard" NC hospital diagnosed approximately 100 HAI each year with estimated costs of $985,000 to $2.7 million. The most common HAI was SSI (73%). Costs related to SSI accounted for 87% to 91% of overall costs. In total, the overall direct annual cost of these 5 selected HAIs was estimated to be between $124.1 and $347.8 million in 2009 for the state of NC.

CONCLUSION

Using conservative estimates, HAI led to costs of more than $100 million in acute care hospitals in the state of NC in 2009. The majority of costs were due to SSI.

Reduction in inappropriate hospital use based on analysis of the causes

Background

To reduce inappropriate admissions and stays with the application of an improvement cycle in patients admitted to a University Hospital. The secondary objective is to analyze the hospital cost saved by reducing inadequacy after the implementation of measures proposed by the group for improvement.

Methods

Pre- and post-analysis of a sample of clinical histories studied retrospectively, in which the Appropriateness Evaluation Protocol (AEP) was applied to a representative hospital sample of 1350 clinical histories in two phases. In the first phase the AEP was applied retrospectively to 725 admissions and 1350 stays. The factors associated with inappropriateness were analysed together with the causes, and specific measures were implemented in a bid to reduce inappropriateness. In the second phase the AEP was reapplied to a similar group of clinical histories and the results of the two groups were compared. The cost of inappropriate stays was calculated by cost accounting. Setting: General University Hospital with 426 beds serving a population of 320,000 inhabitants in the centre of Murcia, a city in south-eastern Spain.

Results

Inappropriate admissions were reduced significantly: 7.4% in the control group and 3.2% in the intervention group. Likewise, inappropriate stays decreased significantly from 24.6% to 10.4%. The cost of inappropriateness in the study sample fell from 147,044 euros to 66,642 euros. The causes of inappropriateness for which corrective measures were adopted were those that showed the most significant decrease.

Conclusions

It is possible to reduce inadequacy by applying measures based on prior analysis of the situation in each hospital.

Three methods for estimating days of hospitalization because of hospital-acquired infection: a comparison

OBJECTIVES

The objective of this study is to compare the three methods internationally used for estimating days of hospitalization attributable to hospital infections by applying them to the same population. The methods are: (1) unmatched comparison group; (2) matched control method-based; and (3) Appropriateness Evaluation Protocol method. A study of the prevalence of infections was performed among patients during hospitalization for an ordinary single sampling department. The survey was completed within eight working days between 15 and 24 October 2007. All patients admitted at least 24 hours to the survey day in each department were included in the study, as well as patients discharged/transferred to another hospital or department. During the prevalence study 621 patients were observed, 70 of which with infection (equal to 11.27%).

METHOD

The 70 uninfected patients needed for comparison using method 1 were selected through a procedure based on propensity score on demographic variables and clinical trials of patients. The Shapiro-Wilk test was used to verify the normality of quantitative variables. In comparing the three methods Kruskall-Wallis test was used (alpha = 0.05), while comparisons between pairs of methods were performed with the Mann-Whitney test (alpha = 0.017).

RESULTS

Estimation results of recovery days with infection using the three comparison tests showed that there is a statistically significant difference between the three methods (P = 0.016) and there is a significant difference between 1 versus 3 (P = 0.013) and between 2 and 3 (P = 0.017), whereas between 1 and 2 no difference was found (P = 0.82).

CONCLUSION

In conclusion, the three methods are not showing the same estimations and thus may not be exchangeable.

Associated factors and cost of inappropriate hospital admissions and stays in a second-level hospital

The objective of this study was to analyze the variables related to inappropriate admissions and hospital stays and their financial repercussions. This was a descriptive retrospective study in which the Appropriateness Evaluation Protocol (AEP) was applied to a representative sample of 725 hospital admissions and 1350 hospital stays. The cost of inappropriate stays was calculated by cost accounting. The study found that 7.4% of admissions and 24.6% of stays were inappropriate. Inappropriate admissions were significantly related to medical specialties and younger patient age. Inappropriate stays were related to these factors, plus patients being outside their corresponding areas, nonurgent admissions, and low occupancy rate. The cost of the inappropriate admissions and stays was 147 044 euros. Extrapolated to the hospital as a whole this would represent 2125638 euros per year. Steps must be taken to reduce inappropriate admissions and stays to lower health care costs and to reserve hospital resources for patients who genuinely need them.

Underresourced hospital infection control and prevention programs: penny wise, pound foolish?

OBJECTIVES

To estimate the cost of healthcare-associated infections (HAIs) in a network of 28 community hospitals and to compare this sum to the amount budgeted for infection control programs at each institution and for the entire network.

DESIGN

We reviewed literature published since 1985 to estimate costs for specific HAIs. Using these estimates, we determined the costs attributable to specific HAIs in a network of 28 hospitals during a 1-year period (January 1 through December 31, 2004). Cost-saving models based on reductions in HAIs were calculated.

SETTING

Twenty-eight community hospitals in the southeastern region of the United States.

RESULTS

The weight-adjusted mean cost estimates for HAIs were $25,072 per episode of ventilator-associated pneumonia, $23,242 per nosocomial blood stream infection, $10,443 per surgical site infection, and $758 per catheter-associated urinary tract infection. The median annual cost of HAIs per hospital was $594,683 (interquartile range [IQR], $299,057-$1,287,499). The total annual cost of HAIs for the 28 hospitals was greater than $26 million. Hospitals budgeted a median of $129,000 (IQR, $92,500-$200,000) for infection control; the median annual cost of HAIs was 4.6 (IQR, 3.4-8.0) times the amount budgeted for infection control. An annual reduction in HAIs of 25% could save each hospital a median of $148,667 (IQR, $74,763-$296,861) and could save the group of hospitals more than $6.5 million.

CONCLUSIONS

The economic cost of HAIs in our group of 28 study hospitals was enormous. In the modern age of infection control and patient safety, the cost-control ratio will become the key component of successful infection control programs.

A model for calculating costs of hospital‐acquired infections: an Italian experience

PURPOSE

Many approaches on the economic aspect of hospital acquired infections (HAIs) have two major limitations: first, the lack of distinction between resources attributable to the management of HAI and resources absorbed by the main clinical problem for which the patient was hospitalized, and second, the lack of an adequate method for calculating the relative costs. These assume that the resources used by HAI can be determined by measuring the extra days of length of days (LOS) of infected patients versus non-infected patients and attribute to extra-LOS a value to the mean total cost. The aim of the article is to test a cost-modelling method that could overcome these limitations by applying the appropriateness evaluation protocol to the medical charts of patients with hospital-acquired symptomatic urinary tract infection (UTI) or sepsis, and by using cost-centre accounting.

DESIGN/METHODOLOGY/APPROACH

The paper explains and tests a model for calculating costs of HAIs.

FINDINGS

The data analysis showed that it is not always true that infections protract LOS: five out of 25 sepsis cases have extra-LOS and eight out of 25 UTI cases have extra-LOS, while the cases of sepsis that arose in surgery ward and intensive care units and urinary tract infections in ICU are without prolongation of LOS. The data analysis also showed that, using the mean total cost, the three cases of sepsis in the general surgery and the six in the ICU did not incur costs, nor did the two cases of UTI in ICU, so that they appear to be infections at zero cost. Moreover, the weight of the cost for the bed, or for the diagnostic services, or for the pharmacological treatment, varied widely depending on the site of the HAI and the ward where the patient was hospitalized.

ORIGINALITY/VALUE

The method can be applied in any hospital.

Comparative cost of selective screening to prevent transmission of methicillin-resistant Staphylococcus aureus (MRSA), compared with the attributable costs of MRSA infection

The annual cost of a screening program to detect methicillin-resistant Staphylococcus aureus (MRSA) in a teaching hospital in Spain was 10,261 Euro. The average cost per MRSA infection was 2,730 Euro; therefore, the cost of the program would be covered if it only prevented 4 infections per year (11% of the total number of MRSA infections at our hospital).

Cost of intensive care unit-acquired bloodstream infections

Intensive care unit-acquired (ICU-acquired) bloodstream infections (BSI) are an important complication of critical illness. The objective of this study was to quantify the excess length of stay, mortality and cost attributable to ICU-acquired BSI. A matched cohort study was conducted in all adult ICUs in the Calgary Health Region between 1 May 2000 and 30 April 2003. One hundred and forty-four patients with ICU-acquired BSI were matched (1:1) to patients without ICU-acquired BSI. Patients with ICU-acquired BSI had a significantly increased median length of ICU stay {15.5 [interquartile range (IQR) 8-26] days vs 12 [IQR 7-18.5] days, P=0.003} and median costs of hospital care [85,137 dollars (IQR 45,740-131,412 dollars) vs 67,879 dollars (IQR 35,043-115,915 dollars, P=0.02) compared with patients without ICU-acquired BSI. The median excess length of ICU stay was two days and the median cost attributable to ICU-acquired BSI was 12,321 dollars per case. Sixty (42%) of the cases died compared with 37 (26%) of the controls [P=0.002, attributable mortality 16%, 95% confidence interval (CI) 5.9-26.0%]. Patients with ICU-acquired BSI were at increased risk for in-hospital death (odds ratio=2.64, 95%CI 1.40-5.29). Among survivor-matched pairs, the median excess lengths of ICU and hospital stay attributable to development of ICU-acquired BSI were two and 13.5 days, respectively, and the attributable cost due to ICU-acquired BSI was 25,155 dollars per case survivor. Critically ill patients who develop ICU-acquired BSI suffer excess morbidity and mortality, and incur significantly increased healthcare costs. These data support expenditures on infection prevention and control programmes and further research into reducing the impact of these infections.

Nosocomial rotavirus infection in European countries: a review of the epidemiology, severity and economic burden of hospital-acquired rotavirus disease

The data currently available on the epidemiology, severity and economic burden of nosocomial rotavirus (RV) infections in children younger than 5 years of age in the major European countries are reviewed. In most studies, RV was found to be the major etiologic agent of pediatric nosocomial diarrhea (31-87%), although the number of diarrhea cases associated with other virus infections (eg, noroviruses, astroviruses, adenoviruses) is increasing quickly and almost equals that caused by RVs. Nosocomial RV (NRV) infections are mainly associated with infants 0-5 months of age, whereas community-acquired RV disease is more prevalent in children 6-23 months of age. NRV infections are seasonal in most countries, occurring in winter; this coincides with the winter seasonal peak of other childhood virus infections (eg, respiratory syncytial virus and influenza viruses), thus placing a heavy burden on health infrastructures. A significant proportion (20-40%) of infections are asymptomatic, which contributes to the spread of the virus and might reduce the efficiency of prevention measures given as they are implemented too late. The absence of effective surveillance and of reporting of NRV infections in any of the 6 countries studied (France, Germany, Italy, Poland, Spain and the United Kingdom) results in severe underreporting of NRV cases in hospital databases and therefore in limited awareness of the importance of NRV disease at country level. The burden reported in the medical literature is potentially significant and includes temporary reduction in the quality of children's lives, increased costs associated with the additional consumption of medical resources (increased length of hospital stay) and constraints on parents'/hospital staff's professional lives. The limited robustness and comparability of studies, together with an evolving baseline caused by national changes in health care systems, do not presently allow a complete and accurate overview of NRV disease at country level to be obtained. RV is highly contagious, and the efficiency of existing prevention measures (such as handwashing, isolation and cohorting) is variable, but low at the global level because of the existence of numerous barriers to implementation (eg, lack of staff, high staff turnover, inadequate hospital infrastructure). Prevention of RV infection by mass vaccination could have a positive impact on the incidence of NRV by reducing the number of children hospitalized for gastroenteritis, therefore reducing the number of hospital cross-infections and associated costs.

Correcting for bias when estimating the cost of hospital-acquired infection: an analysis of lower respiratory tract infections in non-surgical patients

Hospital acquired infections (HAI) are costly but many are avoidable. Evaluating prevention programmes requires data on their costs and benefits. Estimating the actual costs of HAI (a measure of the cost savings due to prevention) is difficult as HAI changes cost by extending patient length of stay, yet, length of stay is a major risk factor for HAI. This endogeneity bias can confound attempts to measure accurately the cost of HAI. We propose a two-stage instrumental variables estimation strategy that explicitly controls for the endogeneity between risk of HAI and length of stay. We find that a 10% reduction in ex ante risk of HAI results in an expected savings of pound 693 ($ US 984).

The use of economic modeling to determine the hospital costs associated with nosocomial infections

Hospital-associated infection is well recognized as a patient safety concern requiring preventive interventions. However, hospitals are closely monitoring expenditures and need accurate estimates of potential cost savings from such prevention programs. We used a retrospective cohort design and economic modeling to determine the excess cost from the hospital perspective for hospital-associated infection in a random sample of adult medical patients. Study patients were classified as being not infected (n=139), having suspected infection (n=8), or having confirmed infection (n=17). Severity of illness and intensive unit care use were both independently associated with increased cost. After controlling for these confounding effects, we found an excess cost of $6767 for suspected infection and $15,275 for confirmed hospital-acquired infection. The economic model explained 56% of the total variability in cost among patients. Hospitals can use these data when evaluating potential cost savings from effective infection-control measures.

SHEA guideline for preventing nosocomial transmission of multidrug-resistant strains of Staphylococcus aureus and enterococcus

BACKGROUND

Infection control programs were created three decades ago to control antibiotic-resistant healthcare-associated infections, but there has been little evidence of control in most facilities. After long, steady increases of MRSA and VRE infections in NNIS System hospitals, the Society for Healthcare Epidemiology of America (SHEA) Board of Directors made reducing antibiotic-resistant infections a strategic SHEA goal in January 2000. After 2 more years without improvement, a SHEA task force was appointed to draft this evidence-based guideline on preventing nosocomial transmission of such pathogens, focusing on the two considered most out of control: MRSA and VRE.

METHODS

Medline searches were conducted spanning 1966 to 2002. Pertinent abstracts of unpublished studies providing sufficient data were included.

RESULTS

Frequent antibiotic therapy in healthcare settings provides a selective advantage for resistant flora, but patients with MRSA or VRE usually acquire it via spread. The CDC has long-recommended contact precautions for patients colonized or infected with such pathogens. Most facilities have required this as policy, but have not actively identified colonized patients with surveillance cultures, leaving most colonized patients undetected and unisolated. Many studies have shown control of endemic and/or epidemic MRSA and VRE infections using surveillance cultures and contact precautions, demonstrating consistency of evidence, high strength of association, reversibility, a dose gradient, and specificity for control with this approach. Adjunctive control measures are also discussed.

CONCLUSION

Active surveillance cultures are essential to identify the reservoir for spread of MRSA and VRE infections and make control possible using the CDC's long-recommended contact precautions.

[Nosocomial bacteremia in the adult patient. Study of associated costs]

OBJECTIVE

Nosocomial infection causes a prolonged hospital stay and an increase in care costs. The objective of this study was to determine the length of stay excess and costs attributable to nosocomial bacteremia.

PATIENTS AND METHODS

Retrospective study of clinical records of 148 patients with nosocomial bacteremia during 1996. A matched case-control study was performed. For matching, the following parameters were used: RDG, year of admission, age 10 years, main diagnosis and number of secondary diagnoses. Costs were determined by excess length of hospital stay and calculating alternative costs.

RESULTS

Matching was obtained for 100 cases (67.5%) and cost estimation was performed. Compared with cases, non-matched cases showed differences regarding significant issues for cost, such as hospital stay ( p = 0.01), number of empirical (p = 0.001) or definitive antibiotics (p = 0.03). The median hospital stay for cases was longer than for controls (35 vs 15.5 days, respectively; p = 0.000). When only survivor case-control pairs were considered (n = 75), cases remained in hospital for a median of 36 vs 15 days for controls (p = 0.000). Hospital stay days attributable to nosocomial bacteremia were 19.5 for all matched and 21 for matched survivor cases. Only 76% of cases had stay days attributable to bacteremia. Significant differences between cases and controls included: the mean total costs of admission (p = 0.000), cost of stay (p = 0.001), pharmaceutical expenses (p = 0.000), and cost of microbiological studies (p = 0.000), laboratory work-up (p = 0.001) and radiological studies (p = 0.000). Hospital stay represented more than 60% of costs, followed by pharmaceutical expenses. Cost differences between bacteremic patients and controls, calculated in function of stay median, was 4.424 euros (p = 0.000) and 4.744 euros (p = 0.000) for alternative costs. Ten cases showed a difference that represented more than half of the total difference.

CONCLUSIONS

Nosocomial bacteremia represent a stay prolongation and a significant economical burden. Hospital stay and pharmaceutical expenses accounted for the most part of the associated costs. The differences in costs obtained with both methods were small. Since not all selected cases were matched, there may be an error in the appreciation of the difference between cases and controls.

Hospital-acquired, laboratory-confirmed bloodstream infection: increased hospital stay and direct costs

OBJECTIVES

To determine increased hospital stay and direct costs attributable to hospital-acquired, laboratory-confirmed bloodstream infection (BSI), and to evaluate the matching variable length of stay (LOS).

DESIGN

Retrospective (historical) cohort study with 1:2 matching in intensive care units and surgical wards.

SETTING

A 2,000-bed university hospital in Rome, Italy.

PATIENTS

All patients admitted between January 1994 and June 1995 who had hospital-acquired, laboratory-confirmed BSI were considered cases; all others were eligible as controls.

METHODS

Two controls (A and B) were selected per case in a stepwise fashion. Controls in group A were selected according to the following six criteria: ward, gender, age, diagnosis, central venous catheter, and LOS equal to the interval from admission to infection in a matched case +/- 20% (LOS +/- 20%). Controls in group B were selected according to the first five criteria, but excluded LOS +/- 20%.

RESULTS

One hundred five of 108 patients were each matched with two controls. The matching appropriateness score was greater than 90%. With the use of controls in groups A and B, the case-fatality rates attributable to hospital-acquired, laboratory-confirmed BSI were 35.2% and 40.9%, respectively; the estimated risk ratios for death were 2.60 and 3.52 (P = .0001), respectively. The increased hospital stay per case attributable to hospital-acquired, laboratory-confirmed BSI was 19.1 (mean) and 13.0 (median) days for matched pairs in control group A and 19.9 (mean) and 15.0 (median) days for matched pairs in control group B. With controls in group A, the cost of increased hospital stay per patient attributable to hospital-acquired, laboratory-confirmed BSI was Euro 15,413. The additional cost per patient due to treatment was Euro 943, making the overall direct cost Euro 16,356 per case.

CONCLUSIONS

This study should make it possible to estimate the cost of hospital-acquired, laboratory-confirmed BSI in most hospitals after adjusting for incidence rate. It also confirmed the use of LOS +/- 20% as a matching variable to limit overestimation of increased hospital stay. To our knowledge, this is among the first such studies in Europe.

Nonrandom selection and the attributable cost of surgical-site infections

OBJECTIVE

To study the extent to which selection bias poses problems for estimating the attributable cost of deep chest surgical-site infection (SSI) following coronary artery bypass graft (CABG) surgery.

DESIGN

Reanalysis of a prospective case-control study.

SETTING

A large, Midwestern community medical center.

PATIENTS

Cases were all patients who had an SSI (N = 41) following CABG and CABG and valve surgery between April 1996 and March 1998. Controls were every tenth uninfected patient (N = 160).

METHODS

Estimates of the attributable cost of deep chest SSI were computed using unmatched comparison, matched comparison, linear regression, and Heckman's two-stage approach.

RESULTS

The attributable cost of deep chest SSI was estimated to be $20,012 by unmatched comparison, $19,579 by matched comparison, $20,103 by linear regression, and $14,211 by Heckman's two-stage method. Controlling for selection bias substantially reduced the cost estimate, but the coefficient capturing selection bias was not statistically significant.

CONCLUSIONS

Deep chest SSI significantly increases the cost of care for patients who undergo CABG surgery. Unmatched comparison, matched comparison, and linear regression estimated the attributable cost to be approximately $20,000. Although controlling for selection bias with Heckman's two-stage method resulted in a substantially smaller estimate, the coefficient for selection bias was not statistically significant, suggesting that the estimates derived from the other models should be acceptable. However, the magnitude of the difference between the models shows that the effect of selection bias can be substantial. Some exploration for selection bias is recommended when estimating the attributable cost of SSIs.

The impact of surgical-site infections following orthopedic surgery at a community hospital and a university hospital: adverse quality of life, excess length of stay, and extra cost

OBJECTIVE

To measure the impact of orthopedic surgical-site infections (SSIs) on quality of life, length of hospitalization, and cost.

DESIGN

A pairwise-matched (1:1) case-control study within a cohort.

SETTING

A tertiary-care university medical center and a community hospital.

PATIENTS

Cases of orthopedic SSIs were prospectively identified by infection control professionals. Matched controls were selected from the entire cohort of patients undergoing orthopedic surgery who did not have an SSI. Matching variables included type of surgical procedure, National Nosocomial Infections Surveillance risk index, age, date of surgery, and surgeon.

MAIN OUTCOME MEASURES

Quality of life, duration of postoperative hospital stay, frequency of hospital readmission, overall direct medical costs, and mortality rate.

RESULTS

Fifty-nine SSIs were identified. Each orthopedic SSI accounted for a median of 1 extra day of stay during the initial hospitalization (P = .001) and a median of 14 extra days of hospitalization during the follow-up period (P = .0001). Patients with SSI required more rehospitalizations (median, 2 vs 1; P = .0001) and more total surgical procedures (median, 2 vs 1; P = .0001). The median total direct cost of hospitalizations per infected patient was $24,344, compared with $6,636 per uninfected patient (P = .0001). Mortality rates were similar for cases and controls. Quality of life was adversely affected for patients with SSI. The largest decrements in scores on the Medical Outcome Study Short Form 36 questionnaire were seen in the physical functioning and role-physical domains.

CONCLUSIONS

Orthopedic SSIs prolong total hospital stays by a median of 2 weeks per patient, approximately double rehospitalization rates, and increase healthcare costs by more than 300%. Moreover, patients with orthopedic SSIs have substantially greater physical limitations and significant reductions in their health-related quality of life.

The cost of antibiotic resistance: effect of resistance among Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudmonas aeruginosa on length of hospital stay

To assess the effect of antimicrobial resistance on length of hospital stay, a case-control study compared infections due to four nosocomial pathogens. Significantly increased lengths of stay were associated with infections due to methicillin-resistant Staphylococcus aureus, extended-spectrum beta-lactamase-producing Klebsiella pneumoniae, and carbapenem-resistant Acinetobacter baumannii or Pseudomonas aeruginosa. Infections with resistant pathogens are associated with prolonged hospitalization.

The economic impact of methicillin-resistant Staphylococcus aureus in Canadian hospitals

OBJECTIVES

To determine the costs associated with the management of hospitalized patients with methicillin-resistant Staphylococcus aureus (MRSA), and to estimate the economic burden associated with MRSA in Canadian hospitals.

DESIGN

Patient-specific costs were used to determine the attributable cost of MRSA associated with excess hospitalization and concurrent treatment. Excess hospitalization for infected patients was identified using the Appropriateness Evaluation Protocol, a criterion-based chart review process to determine the need for each day of hospitalization. Concurrent treatment costs were identified through chart review for days in isolation, antimicrobial therapy, and MRSA screening tests. The economic burden to Canadian hospitals was estimated based on 3,167,521 hospital discharges for 1996 and 1997 and an incidence of 4.12 MRSA cases per 1,000 admissions.

SETTING

A tertiary-care, university-affiliated teaching hospital in Toronto, Ontario, Canada.

PATIENTS

Inpatients with at least one culture yielding MRSA between April 1996 and March 1998.

RESULTS

A total of 20 patients with MRSA infections and 79 colonized patients (with 94 admissions) were identified. This represented a rate of 2.9 MRSA cases per 1,000 admissions. The mean number of additional hospital days attributable to MRSA infection was 14, with 11 admissions having at least 1 attributable day. The total attributable cost to treat MRSA infections was $287,200, or $14,360 per patient The cost for isolation and management of colonized patients was $128,095, or $1,363 per admission. Costs for MRSA screening in the hospital were $109,813. Assuming an infection rate of 10% to 20%, we determined the costs associated with MRSA in Canadian hospitals to be $42 million to $59 million annually.

CONCLUSIONS

These results indicate that there is a substantial economic burden associated with MRSA in Canadian hospitals. These costs will continue to rise if the incidence of MRSA increases further.

Estimation of extra hospital stay attributable to nosocomial infections: heterogeneity and timing of events

Infections acquired in hospital are likely to affect the duration of hospitalization. Suitable statistical methods for estimating the extra days spent in hospital due to nosocomial infections should allow modeling of the heterogeneity of the patient population and the timing of events, as failure to account for important covariates and failure to model adequately the timing of events may lead to biased results. Three approaches have been used in the past to estimate the extra stay: a comparison of duration of stay of infected and uninfected patients, matching of infected and uninfected patients with respect to potentially important determinants of the length of hospital stay, and matching for time-to-infection in addition to the other factors. While these approaches can allow for the heterogeneity of the patient population, none takes sufficient account of the real timing of events and may overestimate the effect of nosocomial infections. We explored the statistical methods available for analyzing time-to-event data and derived alternative methods to estimate the extra stay that appropriately account for heterogeneity and timing. Data from two prospective cohort studies on postoperative wound infection and on nosocomial pneumonia showed that the two-group comparison yields the highest estimates of extra stay (21 and 14 extra days), while matching for confounders and time reduced the estimates to 11 and 8 extra days; our methods yield even lower results (10-12 and 3-4 extra days).

Quantifying excess length of postoperative stay attributable to infections: a comparison of methods

To quantify the net effect of deep surgical site infection (DSSI) on postoperative stay (POS) among patients who had undergone open heart surgery, and to assess the comparability of two methods, two observational studies were conducted: one on a retrospective cohort of 701 operated patients, and the other on a cohort of 31 infected patients versus a cohort of uninfected patients, with 1:1 matching. In addition to DSSI, a further three factors were identified by multivariate analysis as independent POS-related predictor variables. After internal validation of the multivariate model, excess POS attributable to DSSI amounted to 20.7 days (95% confidence interval [CI] 16.7-24.9). In contrast, excess length of stay attributable to DSSI among the matched pairs who survived infection (22) totaled 14.3 days (95% CI 3.2-25.4) and 26.5 days (mean and median differences). Multivariate techniques may prove a more appropriate and reliable analysis than matched-pair comparisons for the purpose of evaluating the extra stay and cost attributable to the nosocomial infections.

The economic impact of Staphylococcus aureus infection in New York City hospitals

We modeled estimates of the incidence, deaths, and direct medical costs of Staphylococcus aureus infections in hospitalized patients in the New York City metropolitan area in 1995 by using hospital discharge data collected by the New York State Department of Health and standard sources for the costs of health care. We also examined the relative impact of methicillin-resistant versus -sensitive strains of S. aureus and of community-acquired versus nosocomial infections. S. aureus-associated hospitalizations resulted in approximately twice the length of stay, deaths, and medical costs of typical hospitalizations; methicillin-resistant and -sensitive infections had similar direct medical costs, but resistant infections caused more deaths (21% versus 8%). Community-acquired and nosocomial infections had similar death rates, but community-acquired infections appeared to have increased direct medical costs per patient ($35,300 versus $28,800). The results of our study indicate that reducing the incidence of methicillin-resistant and -sensitive nosocomial infections would reduce the societal costs of S. aureus infection.

Measuring the costs of nosocomial infections: methods for estimating economic burden on the hospital

To compete more effectively for resources, it is increasingly important for infection control practitioners to estimate the costs of nosocomial infections and the amount of money their infection control programs save the hospital. Studies on costs should estimate both extra length of stay and extra costs attributable to infectious complications. Cost estimates should either adjust charges by a cost to charge ratio, which is relatively easy, or estimate hospital costs directly by detailed cost-accounting, which is comparatively more difficult. If there is insufficient time to measure costs concurrently in every infected patient, comparative studies can be done by comparing infected and uninfected patients matched on characteristics that control for the preexisting differences between them. Diagnosis-related groups and the number of diagnoses appear to be useful matching variables because they are strongly associated with both nosocomial infection and length of stay. The final results should be expressed as either potential or actual savings to the hospital, depending on whether significant reductions in nosocomial infection rates have been achieved.

Cost of nosocomial infection: relative contributions of laboratory, antibiotic, and per diem costs in serious Staphylococcus aureus infections

This study reports an analysis of the relative importance of laboratory antibiotic, and per diem costs of caring for 58 patients with serious Staphylococcus aureus nosocomial infections. Laboratory costs accounted for 2%, antibiotics for 21%, and per diem costs for 77% of total infection-related costs. Only 45% of patients were hospitalized for additional days specifically because of infection, but these patients stayed an average of 18 extra days. Nosocomial infections with S. aureus resistant to penicillinase-resistant penicillins (PRP) were more frequently associated with additional infection-related days of hospitalization than were PRP-susceptible infections. The cost of PRP-resistant infections was also significantly greater than PRP-susceptible infections, primarily because of the costs of additional days of hospitalization. Rational strategies to control costs of nosocomial infection should focus on two approaches: (1) prevention and (2) reduction of acute hospital days attributable to infections.