Among HIV-positive patients who were hospitalized with PCP and bacterial pneumonia, we found the following risk factors for early readmission: leaving hospital AMA, living in the poorest neighborhood, the index admission occurring during the summer months and being hospitalized in the preceding 6 months. Our 2-week readmission rates were substantially higher than those reported by Grant et al.4
(PCP: 21% vs 4.2%; BP: 15% vs 6.5%). Our patients had higher median CD4 cell counts than Grant's cohort (cases, 65 vs 19 cells/mm3
; controls, 160 vs 26 cells/mm3
), who appeared to be in more-advanced stages of AIDS. This large difference in readmission rates may be due to differences in population and health care systems. Furthermore, the difference in CD4 counts between cases and controls may reflect the possibilities that patients with readmissions were more likely to have had HIV for longer periods of time, that they had been less likely to take HAART, or that they had higher rates of nonadherence or drug therapy resistance or failure.
Leaving hospital against medical advice was the strongest predictor of readmission. In an earlier study, we found that leaving on welfare check day and a history of IDU were significant predictors of discharge AMA among hospitalized HIV-infected patients.13
In addition, these patients leaving AMA, when compared to those formally discharged, were found to be readmitted more frequently (frequency ratio:95% C.I., 1.25:1.11 to 1.42), be more likely to be readmitted with a related diagnosis within 30 days (OR, 5.00; 95%CI, 3.04 to 8.24) and to have significantly longer length of stay in the follow-up period. Other studies have found that patients who leave AMA tend to be younger,14,15
to be of a lower income level,15
and to have no primary care physician.14
As in our earlier study,13
patients who leave AMA are more likely to be substance users,14,16
and to use psychoactive drugs more frequently than patients discharged formally.16
In addition, patients who are discharged AMA may have negative preconceptions about hospital stays and feel that hospital staff are not helpful.17,18
Because leaving hospital AMA is an indicator of incomplete therapy, it may negatively affect the health outcomes of the patients,14
leading to rapid rehospitalization.16,17
Patients who leave AMA are up to 7 times more likely to be readmitted than those formally discharged.14
In addition, Weingart et al. suggest that a patient who leaves AMA may not be able to remain in hospital for the duration of treatment for personal reasons, and would return after they have addressed other needs.15
Low income is correlated with AMA discharges,15
and among HIV-infected persons residing in the poorest neighborhood, welfare check issue day may influence their decision to leave the hospital prematurely.13
Grant et al. found that leaving the hospital unaccompanied by family or friend was independently associated with hospital readmission.4
This factor may represent a sensitive measure of social isolation even better than living situation, because living situation (as well as other indicators of social isolation) was not different between cases and controls. Illicit drug use and poor social support also have been associated with higher rehospitalization rates.1,4,19–21
Another study found that schizophrenic patients whose family members came to visit them were less likely to have early rehospitalizations.19
They suggested that the social environment of the discharged individual might influence the course of recovery. The problems associated with lack of social support are important to examine in the context of our study population. In our cohort, we found that readmissions were significantly associated with living in the poorest urban neighborhood, where illicit drug use is alarmingly high.22
As Grant et al.4
hypothesized, concomitant AIDS diagnoses were not predictive of early hospital readmission in the era of HAART; however, recent antecedent hospitalization continues to be associated with readmission and may reflect suboptimal management of HIV disease. There was a trend for the controls to be discharged on HAART or scheduled to see a prescribing physician regarding HAART as an outpatient compared to cases. Unfortunately, more case patients left hospital AMA, precluding arrangement for this complex therapeutic regimen.
Prior admission within the past 6 months was associated with early readmission, which has been confirmed elsewhere.4
The number of prior admissions has been found to be a strong predictor of future rehospitalization.23
One study showed that patients who were readmitted were significantly more likely than those who were not readmitted to have had 4 or more prior hospitalizations.19
This may be explained by the notion that frequently hospitalized patients tend to be chronically ill and are often rehospitalized for the same illness.20
In addition, we unexpectedly found that hospitalization in the summer months was associated with higher risk for readmission. The reason for this is unclear, because we controlled for leaving AMA that may occur more frequently in the summer months.
Limitations of our study include retrospective data collection and clinical data that were limited to the subsample of patients on the HIV/AIDS ward. As in the study by Grant et al.,4
during the pre-HAART era, we limited our diagnoses to BP and PCP, because they are common and reliably diagnosed. Data on non-injection drug use were not specifically collected. We probably underestimated the number of readmissions, because we studied only 1 hospital, although the patients served by this hospital tend to come back for their medical care because it is a well-known AIDS tertiary care center with a specialized HIV/AIDS ward.24,25
It is possible, however, that injection drug users are being readmitted elsewhere and this may explain why it was not significantly associated with hospital readmission. In addition, the patients from the poorest urban neighborhood who leave AMA may be the type of patient who would re-present to the same hospital. The sample size may have been too small in the subanalysis to identify other factors of interest that are associated with readmission. Finally, the odds ratios derived from case-control are somewhat inflated, and a longitudinal study would provide more precise estimates.
On the basis of our findings, we recommend identifying HIV-infected patients who are at risk for early readmission, such as those with recent hospitalizations and those who live in poorer urban neighborhoods. A social worker might be able to explore and address some of the underlying reasons that these patients leave hospital AMA; this could alleviate the health and economic burden of potentially avoidable readmissions in this vulnerable population.