Methods for estimating days of hospitalization due to nosocomial infections

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.

Healthcare-Associated Infections Due to Multidrug-Resistant Organisms: a Surveillance Study on Extra Hospital Stay and Direct Costs

BACKGROUND

The increasing antimicrobial resistance poses a challenge to surveillance systems and raises concerns about the impact of multidrug-resistant organisms on patient safety.

OBJECTIVE

The study aimed to estimate extra hospital stay and economic burden of infections due to alert organisms - mostly multidrug-resistant - in a teaching hospital.

METHODS

The present retrospective matched cohort study was conducted based on the analysis of hospital admissions at Sant'Andrea Teaching Hospital in Rome from April to December 2015. Extra hospital stay was the difference in the length of stay between each case and control. All the patients developing an infection due to an alert organism were considered cases, all others were eligible as controls. The costs of LOS were evaluated by multiplying the extra stay with the hospital daily cost.

RESULTS

Overall, 122 patients developed an infection due to alert organisms and were all matched with controls. The attributable extra stay was of 2,291 days (mean 18.8; median 19.0) with a significantly increased hospitalization in intensive care units (21.2 days), bloodstream infections (52.5 days), and infections due to Gram-negative bacteria (mean 29.2 days; median 32.6 days). Applying the single day hospital cost, the overall additional expenditure was 11,549 euro per patient. The average additional cost of antibiotic drugs for the treatment of infections was about 1,200 euro per patient.

CONCLUSION

The present study presents an accurate mapping of the clinical and economic impact of infections attributable to alert organisms demonstrating that infections due to multidrug-resistant organisms are associated with higher mortality, longer hospital stays, and increased costs. Article Highlights Box: The increasing antimicrobial resistance poses a challenge for surveillance systems and raises concerns about the impact of multidrug-resistant organisms on patient safety. • Healthcare-associated infections (HAIs) have historically been recognized as a significant public health problem requiring close surveillance. • Despite several and reliable findings have been achieved on clinical issues, our knowledge on the economic impact of healthcare-associated infections due to multidrug-resistant organisms needs to be widened. • Estimating the cost of infections due to multidrug-resistant organisms in terms of extra hospital stay and economic burden is complex, and the financial impact varies across different health systems. • Evaluations of social and economic implications of hospital infections play an increasingly important role in the implementation of surveillance systems. • The costs of infection prevention and control programs and dedicated personnel are relatively low and self-sustainable when efficient.

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.

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.

Variations in analytical methodology for estimating costs of hospital-acquired infections: a systematic review

Quantifying the additional costs of hospital-acquired infections (COHAI) is essential for developing cost-effective infection control measures. The methodological approaches to estimate these costs include case reviews, matched comparisons and regression analyses. The choice of cost estimation methodologies can affect the accuracy of the resulting estimates, however, with regression analyses generally able to avoid the bias pitfalls of the other methods. The objective of this study was to elucidate the distributions and trends in cost estimation methodologies in published studies that have produced COHAI estimates. We conducted systematic searches of peer-reviewed publications that produced cost estimates attributable to hospital-acquired infection in MEDLINE from 1980 to 2006. Shifts in methodologies at 10-year intervals were analysed using Fisher's exact test. The most frequent method of COHAI estimation methodology was multiple matched comparisons (59.6%), followed by regression models (25.8%), and case reviews (7.9%). There were significant increases in studies that used regression models and decreases in matched comparisons through the 1980s, 1990s and post-2000 (P = 0.033). Whereas regression analyses have become more frequently used for COHAI estimations in recent years, matched comparisons are still used in more than half of COHAI estimation studies. Researchers need to be more discerning in the selection of methodologies for their analyses, and comparative analyses are needed to identify more accurate estimation methods. This review provides a resource for analysts to overview the distribution, trends, advantages and pitfalls of the various existing COHAI estimation methodologies.

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.

Factors related to hospital stay among patients with nosocomial infection acquired in the intensive care unit

OBJECTIVES

To assess the influence of nosocomial infection on length of stay in the intensive care unit (ICU) and to determine the relative effect of other factors on extra length of hospitalization associated with nosocomial infection.

DESIGN

Prospective cohort multicenter study in the context of the ENVIN-UCI project.

SETTING

Medical or surgical ICUs of 49 different hospitals in Spain.

METHODS

All consecutive patients (N = 6,593) admitted to ICUs of the participating hospitals who stayed for more than 24 hours during a 3-month period (from January 15 to April 15, 1996) were included. Length of ICU stay was compared between patients with and without nosocomial infections. RESULTS Uninfected patients (N = 5,868) had a median stay in the ICU of 3 days, whereas the median for infected patients (N = 725) was 17 days (P < .001). The median for infected patients with one episode of nosocomial infection was 13 days. The greatest length of stay (40 days) was among patients admitted to the ICU because of medical diseases, with an infection acquired before admission to the ICU, and with the largest number of nosocomial infection episodes. In extended stays, nosocomial infection was significantly associated with length of hospitalization (day 21; odds ratio, 22.38; 95% confidence interval 16.6 to 30.4), whereas an effect of variables related to severity of illness on admission (Acute Physiology and Chronic Health Evaluation II score, urgent surgery, and infection prior to ICU admission) was not found.

CONCLUSIONS

The presence of nosocomial infection and the number of infection episodes were the variables with the strongest association with prolonged hospital stay among ICU patients.

Impact of infection by vancomycin-resistant Enterococcus on survival and resource utilization for patients with leukemia

We estimated the impact of vancomycin-resistant Enterococcus (VRE) infection on the outcomes of patients with leukemia in a case-control study. Compared with their matched controls (n = 45), cases (n = 23) had 22% greater total charges and shorter survival (P = .04). These findings substantiate the need for aggressive interventions to prevent VRE transmission.

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.

Assessing excess nurse work load generated by multiresistant nosocomial bacteria in intensive care

OBJECTIVE

To compare three methods for assessing the excess nurse work load related to recommended procedures for managing nosocomial infections (NI) due to multiresistant bacteria (MRB): two activity scores, the Omega score and the Projet de Recherche en Nursing (PRN) system, and a specific evaluation based on functional analysis of nursing procedures.

SETTING

10 beds in a medical intensive care unit (MICU).

PATIENTS

Patients admitted from November 15, 1995, to June 15, 1996, were included and divided in two groups based on presence of MRB colonization or infection (MRB+ and MRB-groups).

METHODS

Data were collected regarding length of stay (LOS) in days; Omega score for the entire stay; PRN score for the entire stay and per day; and time required to perform correctly four nursing procedures related to MRB NI, as evaluated specifically by the nursing staff, using a detailed functional analysis document that described all elementary nursing tasks in chronological order and all material needed to carry out those tasks.

RESULTS

The LOS and total Omega and PRN scores were higher in the MRB+ group than in the MRB- group: LOS, 23 +/- 20.6 versus 12 +/- 15.3 days, (P<.001); Omega score, 164 +/- 103.4 versus 123 +/- 93.7 points (P<.001); PRN score, 3,606 +/- 3,187 versus 1,854 +/- 2,356 points (P<.001), respectively. The daily PRN score was also higher in MRB+ group (PRN, 160 +/- 25 vs 146 +/- 34 points in the MRB- group; P<.028). Four nursing procedures made necessary by MRB acquisition were identified: isolation precautions, with two levels according to whether the risk of contamination was mild-moderate or high; bathing the patient with antiseptic solution; bedpan management; and microbiological screening. The functional analysis indicated that the time needed to carry out these four procedures correctly was 245 minutes per patient per day, as compared to 85 minutes according to the PRN system.

CONCLUSIONS

Our data confirm that MRB NIs are responsible for an increase in nurse work load, as estimated by LOS, Omega, and PRN scores. However, the daily excess nurse work load related directly to recommended procedures for managing MRB NIs in MICUs is underestimated by these activity scores, as compared to a specific functional analysis of nursing tasks. This may be of importance in evaluating potential links between nurse work load and MRB NIs and in determining the number of nurse hours needed to comply with infection control recommendations.

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.

Prolongation of hospital stay and extra costs due to hospital-acquired infection in a neonatal unit

A case-control study to evaluate the mean extra stay and corresponding cost of neonates acquiring a hospital-acquired infection (HAI) was performed on all patients admitted to a neonatology unit and discharged alive in 1994. Cases were identified from medical records. Controls were matched to cases for birthweight, gestational age, mode of admission to the unit, previous stay in an intensive care unit and presence of a central venous catheter. Costs were taken as those of the extra days attributable to HAI, i.e. the mean difference in the length of stay between cases and controls. Among a cohort of 616 neonates, 34 (5.5%) had one or more HAIs (average = 1.1). The mean extra cost per infected case was 52,192 FF (US$10,440), corresponding to 5.2 extra days in hospital.

Estimated costs of postoperative wound infections. A case-control study of marginal hospital and social security costs

A cohort of 4515 surgical patients in ten selected intervention groups was followed. Three hundred and seventeen developed postoperative wound infections, and 291 of these cases were matched 1:1 to controls by operation, sex and age. In comparison to the controls the cases stayed longer in hospital after the intervention and had more contact after discharge with the social security system. Using data from a national sentinel reference database of the incidence of postoperative wound infections, and using national activity data, we established an empirical cost model based on the estimated marginal costs of hospital resources and social sick pay. It showed that the hospital resources spent on the ten groups, which represent half of the postoperative wound infections in Denmark, amounted to approximately 0.5% of the annual national hospital budget. This stratified model creates a better basis for selecting groups of operations which need priority in terms of preventive measures.