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From *the Centre for Health Evaluation and Outcome Sciences, St. Paul's Hospital,
the Department of Medicine, St. Paul's Hospital and the University of British Columbia,
the British Columbia Centre for Excellence in HIV/AIDS,
the Department of Health Care and Epidemiology, University of British Columbia, ¶the Pharmacoeconomic Program, St. Paul's Hospital, and **the Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC
Correspondence to: Dr. Anita Palepu, Rm. 620B, St. Paul's Hospital, 1081 Burrard St., Vancouver BC V6Z 1Y6; fax 604 806-8005; anita{at}hivnet.ubc.ca
| Abstract |
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Methods: The Vancouver Injection Drug User Study (VIDUS) is a prospective cohort study involving IDUs that began in 1996. Our analyses were restricted to the 598 participants who gave informed consent for our study. We used the participants' responses to the baseline VIDUS questionnaire and, from medical records at St. Paul's Hospital, Vancouver, we collected detailed information about the frequency of emergency department visits, hospital admissions and the primary diagnosis for all visits or hospital stays between May 1, 1996, and Aug. 31, 1999. The incremental difference in hospital utilization costs by HIV status was estimated, based on 105 admissions in a subgroup of 64 participants.
Results: A total of 440 (73.6%) of the 598 IDUs made 2763 visits to the emergency department at St. Paul's Hospital during the study period. Of these 440, 265 (60.2%) made frequent visits (3 or more). The following factors were associated with frequent use: HIV-positive status (seroprevalent: adjusted odds ratio [OR] 1.7, 95% confidence interval [CI] 1.22.6; seroconverted during study period: adjusted OR 3.0, 95% CI 1.65.7); more than 4 injections daily (adjusted OR 1.5, 95% CI 1.12.1); cocaine use more frequent than use of other drugs (adjusted OR 2.0, 95% CI 1.23.6); and unstable housing (adjusted OR 1.5, 95% CI 1.12.2). During the study period 210 of the participants were admitted to hospital 495 times; 118 (56.2%) of them were admitted frequently (2 or more admissions). The 2 most common reasons for admission were pneumonia (132 admissions among 79 patients) and soft-tissue infections (cellulitis and skin abscess) (90 admissions among 59 patients). The following factors were independently associated with frequent hospital admissions: HIV-positive status (seroprevalent: adjusted OR 5.4, 95% CI 3.48.6; seroconverted during study period: adjusted OR 2.9, 95% CI 1.46.0); and female sex (adjusted OR 1.8, 95% CI 1.13.1). The incremental hospital utilization costs incurred by HIV-positive IDUs relative to the costs incurred by HIV-negative IDUs were $1752 per year.
Interpretation: Hospital utilization was significantly higher among community-based IDUs with early HIV disease than among those who were HIV negative. Much of the hospital use was related to complications of injection drug use and may be reduced with the establishment of programs that integrate harm reduction strategies with primary care and addiction treatment.
Because hospital admissions among HIV-positive IDUs are largely attributable to complications of injection drug use10 that are not directly related to the HIV infection, it is unclear whether community-based HIV-negative IDUs have similar hospital utilization patterns as IDUs with early HIV disease. Other studies of health care use by IDUs have been in the setting of drug treatment or clinics and reflect a highly selected population.11,12 We therefore conducted this study to determine the predictors of frequent emergency department use among community-based IDUs. We also examined the predictors of frequent hospital admission and reviewed the primary diagnosis for each encounter. To assess whether there was a difference in hospital utilization costs according to HIV status, we estimated the incremental costs incurred by IDUs with early stage disease relative to costs incurred by HIV-negative IDUs. With the rising prevalence of HIV infection among IDUs in many Canadian cities, including Vancouver,13,14 these data may be crucial for planning and evaluating programs that provide appropriate health care services to reduce drug-related harm among active IDUs with or at risk of HIV infection.
| Methods |
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Hospital utilization costs were estimated according to the inpatient resource-utilization profiles of a random sample of 64 participants who were admitted to hospital during the study period. Our cost estimates were for the first 105 admissions. For each admission, information was abstracted from the medical records, including the nursing ward, medications received, investigations, physicians' visits and length of stay. To distinguish between costs and charges,15 we estimated inpatient unit costs using a model of simultaneous allocation16 of all expenditures including overhead, opportunity cost of hospital resources as well as a 5% global depreciation of capital equipment.
Contingency tables were used to examine associations between frequent users and nonfrequent users of the emergency department and hospital by their HIV status and other sociodemographic and behavioural characteristics. We defined a priori frequent emergency department use as 3 or more visits and frequent hospital admission as 2 or more stays during the study period. We classified HIV status as seroprevalent (n = 166), seroconverted (for HIV seroconversions that occurred during the study period) (n = 51) and negative (n = 381). Unstable housing was defined as living in a single-occupancy room hotel, boarding room, hostel, transition house, jail or on the street in the 6 months before enrolment in the study.3,13 The Wilcoxon rank-sum test was used to compare continuous variables.
To identify independent predictors of frequent emergency department use, variables significant at the 0.05 level in the univariate analysis were entered into logistic regression models in a stepwise, hierarchical fashion. In the final model, all relevant 2-way interactions were considered. This procedure was also performed to identify predictors of frequent hospital admission. We also compared self-reported hospital admissions in the 6 months before entry into the study and at follow-up (1999) by HIV status to assess the extent to which HIV-negative IDUs could have been admitted to hospital elsewhere.
To estimate the incremental difference in hospital utilization costs between IDUs with early HIV infection and HIV-negative IDUs, the average daily cost was multiplied by the median length of stay and then the annualized frequency of hospital admission per person by HIV status.17 We performed 2-way sensitivity analyses using the lower and upper limits of the 95% confidence interval (CI) for the hospital utilization costs and simultaneously varying the length of stay by calculating the difference in length of stay by HIV status using the 25th and 75th percentiles.
| Results |
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Of the 598 participants included in our analysis, 440 (73.6%) of them visited the emergency department a total of 2763 times during the 39-month study period. Of these 440 IDUs, 265 (60.2%) visited the emergency department frequently and 91 (20.7%) visited more than 10 times. The annualized frequency of emergency department use by HIV status was 2.6 for the IDUs with seroprevalent HIV infection (1171 visits among 137 patients), 2.9 for the IDUs with seroconverted HIV infection (387 visits among 41 patients) and 1.4 for the HIV-negative IDUs (1205 among 262 patients). The 2 most common reasons for visiting the emergency department were soft-tissue infections (cellulitis and skin abscess) and problems directly related to illicit drug use (e.g., drug intoxication, overdose and drug withdrawal) (Table 1).
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Overall, 210 (35.1%) of the 598 participants were admitted to the hospital 495 times during the study period. Of these 210, 118 (56.2%) were admitted frequently and 21 (10.0%) had 5 or more admissions. The annualized frequency of hospital admissions by HIV status was 0.89 for the IDUs with seroprevalent HIV infection (294 admissions among 102 patients), 0.80 for the IDUs with seroconverted HIV infection (52 admissions among 20 patients) and 0.52 for the HIV-negative IDUs (149 admissions among 88 patients). The 2 most common reasons for admission were pneumonia (132 admissions among 79 patients) and soft-tissue infections (cellulitis and skin abscess, 90 admissions among 59 patients) (Table 1). The HIV-negative IDUs were less likely than the HIV-positive IDUs to report hospital admissions in the 6 months before entry into the study (odds ratio [OR] 0.43, 95% CI 0.290.67) and in the 6 months before follow-up (OR 0.48, 95% CI 0.290.77).
The crude and adjusted ORs for the predictors of frequent emergency department use and frequent hospital admission are shown in Tables 2 and 3 respectively. Logistic regression analysis showed that frequent emergency department use was associated with HIV infection (seroprevalent: adjusted OR 1.7, 95% CI 1.22.6; seroconverted: adjusted OR 3.0, 95% CI 1.65.7), injection more than 4 times daily (adjusted OR 1.5, 95% CI 1.12.1), cocaine use more frequent than use of other drugs; adjusted OR 2.0, 95% CI 1.23.6) and unstable housing (adjusted OR 1.5, 95% CI 1.12.2). The following factors were independently associated with frequent hospital admission: HIV infection (seroprevalent: adjusted OR 5.4, 95% CI 3.48.6; seroconverted: adjusted OR 2.9, 95% CI 1.46.0) and female sex (adjusted OR 1.8, 95% CI 1.13.1).
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Utilization costs
The 64 IDUs included in the subgroup cost analysis were admitted to hospital 184 times during the study period. Of the 64 participants, 33 had seroprevalent HIV infection at baseline and 5 became HIV positive during the study period, with a median CD4 count of 389
106/L (interquartile range [IQR] 216592
106/L) at their first hospital admission. The 5 who became HIV positive during the study period had not been admitted to hospital when they were HIV negative. The IDUs who were HIV-positive had a longer length of stay (median 7 days, IQR 512 days) than the HIV-negative IDUs (median 5 days, IQR 48 days). The annualized frequency of hospital admissions was 0.96 among the seroprevalent HIV-positive IDUs and 0.77 among the HIV-negative IDUs. The fully allocated average hospital utilization cost per day was $610.33 (95% CI $575.70$644.96). The incremental hospital utilization cost incurred by the HIV-positive IDUs relative to the HIV-negative IDUs was $1752 per year (the sensitivity analyses showed that the incremental cost varied from $990 to $3457 per year).
| Interpretation |
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Our finding that female sex was an independent predictor of frequent hospital admission is consistent with previous findings.6,18,19 The recent HIV Costs and Services Utilization Study in the United States reported that the suboptimal pattern of care among women and IDUs was largely mitigated by adjusting for insurance coverage and race or ethnic background.20 Comparisons with US findings are difficult given differences in the health care systems and the demographic composition of the study populations. The association between the use of cocaine and unstable housing with frequent emergency department use has been noted elsewhere.21,22,23,24
The predominant reasons for hospital admission (pneumonia and soft-tissue infections) in our study are directly and indirectly related to needle use and highlight the importance of counselling and providing the tools necessary to practise safe injection techniques. In a study by Stein,10 HIV-positive IDUs were admitted to an urban hospital primarily because of injection-related complications. In another study, involving IDUs in drug treatment, those with early HIV infection used more ambulatory and inpatient services than HIV-negative IDUs.12 An increased biological susceptibility to bacterial infections8,25 or poor hygiene and high-risk drug injection practices13,26 are possible explanations for the higher frequency of hospital admissions among HIV-positive IDUs.
Our study had several limitations. First, we may have underestimated the emergency department and hospital use because the participants may have received care from other hospitals. Second, we did not capture outpatient clinic visits. Third, we used a relatively small sample of IDUs to estimate the hospital utilization costs. Finally, the study participants may not be representative of all IDUs, because those in the lowest socioeconomic group may have been overrepresented in our study population.
Our cost analysis builds on previous work in that we examined actual hospital costs for IDUs by assigning fully allocated costs of actual resource use. In other studies costs were derived from charge data,4,10,27 or aggregated service utilization costs were used to calculate costs per patient-year.28,29 The incremental hospital utilization costs incurred by the HIV-positive IDUs relative to the costs incurred by the HIV-negative IDUs were $1752 per person; this translates into an additional $197 976 per year for hospital care for the 113 HIV-positive IDUs who were admitted to hospital during our study period.
A recent study reported high hospital use and costs among poor people in Toronto.30 Our results provide some reasons for their findings among the IDU subgroup. Much of the health care use was largely attributable to complications of injection drug use, regardless of HIV status. The use of sterile injecting equipment and safe injection practices might have prevented many of these conditions and, thus, reduced the need for emergency department visits or hospital admissions.31,32 Programs that integrate harm reduction strategies with primary care and addiction treatment33,34 should be considered by jurisdictions serving this vulnerable population.
| Acknowledgments |
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This research was funded by the British Columbia Health Research Foundation, the National Institutes of Health (grant R01 DA11591-01), the British Columbia Ministry of Health and Health Canada. Anita Palepu was supported by a National Health Research Scholar Award from the National Health Research and Development Program of Health Canada, and Martin Schechter was supported by a National AIDS Research Scientist Award.
| Footnotes |
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Contributors: Anita Palepu was the principal author, conceived and designed the study and was responsible for the interpretation of the data. Mark Tyndall was responsible for the analysis and interpretation of the data and for revising the manuscript. Hector Leon was responsible for the costing of the hospital resource use profiles and for revising the manuscript. Jennifer Muller was responsible for data collection and linkage to the Vancouver Injection Drug User Study survey data and for revising the mansucript. Michael O'Shaughnessy and Martin Schechter contributed to the interpretation of the data and revision of the manuscript. Aslam Anis contributed to the study design, was responsible for the costing methodology and interpretation and for revising the manuscript.
Competing interests: None declared.
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