Trial Design

This investigator-initiated, randomized, controlled trial was approved by institutional review boards at Cooper University Hospital, the National Bureau of Economic Research, Kennedy Health, and Our Lady of Lourdes Medical Center. The trial protocol, available with the full text of this article at NEJM.org, and planned analyses were publicly prespecified in March 2014 in consultation with Dr. Jeffrey Brenner, then director of the Coalition. Minor departures from the plan developed before analysis are described in the Supplementary Appendix, available at NEJM.org. The Coalition staff implemented the protocol and administered the intervention for patients in the treatment group but were unaware of the results until the trial was completed.

Program

Eligibility

The Camden Core Model is a care-transition program designed to improve patient health and reduce hospital use among some of the least healthy and most vulnerable adults in the United States. Eligibility for trial participation was limited to adults 18 to 80 years of age living in Camden, New Jersey, which is one of the most economically depressed cities in the country and has a high rate of violent crime10; in 2017, 37% of Camden residents lived below the poverty line as compared with 15% of persons in the United States overall.30

The intervention targeted superutilizers of the health care system — persons with medically and socially complex needs who have frequent hospital admissions. The inclusion criteria were at least one hospital admission at any of four Camden-area hospital systems in the 6 months before the index admission, when patients were enrolled; at least two chronic conditions; and at least two of the following traits or conditions: use of at least five active outpatient medications, difficulty accessing services, lack of social support, a coexisting mental health condition, an active drug habit, and homelessness. Patients were excluded if they were uninsured, had cognitive impairment, or were receiving oncologic care or had been admitted for a surgical procedure for an acute health problem, for mental health care (with no coexisting physical health conditions), or for complications of a progressive chronic disease for which limited treatments were available. The eligible population composed less than 0.5% of the Camden population but accounted for 11% of the city’s hospital expenditures (see the Supplementary Appendix).

Intervention

The time-limited intervention had intensive clinical and social components. Patients were enrolled while in the hospital. Once they returned home, patients worked with a multidisciplinary team that included registered nurses, social workers, licensed practical nurses, community health workers, and health coaches. The team conducted home visits, scheduled and accompanied patients to initial primary and specialty care visits, coordinated follow-up care and medication management, measured blood pressure and blood sugar levels, coached patients in disease-specific self-care, and helped patients apply for social services and appropriate behavioral health programs. The intervention contained many characteristics considered important for successful care-transition programs for high-cost, high-need patients.31,32 The Supplementary Appendix includes more details on the intervention.

The control group received usual postdischarge care, which may have included home health care services or other forms of outreach. We were unable to measure the postdischarge services received by the control group.

Recruitment and Randomization

Recruitment took place at Cooper University Hospital and Our Lady of Lourdes Hospital. Using the Camden Coalition Health Information Exchange database — which provided daily updates from hospital electronic medical records at these hospitals and the Virtua Health System and the Kennedy Health System (as of July 2014) — staff selected potentially eligible patients, who formed the triaged population. A Coalition recruiter approached these patients in the hospital, confirmed their eligibility, obtained written informed consent, and conducted a baseline survey. The recruiter then used a tamper-proof and externally recorded randomization process to assign treatment or control status and informed the patient of the assignment. All patients who completed the baseline survey were compensated with $20 for their time. Details regarding recruitment and randomization are available in the Supplementary Appendix.

Figure 1. Figure 1. Screening, Randomization, and Analysis. Data are from the Camden Coalition Health Information Exchange. Patients who declined to participate explicitly said “no” to the offer of randomization. Patients who gave a soft decline did not provide consent when approached but did not decline to participate and could be approached again during future hospitalizations if they were otherwise eligible. Patients who were unable to provide consent were either discharged or died before they could be reached or were unable to consent for reasons such as being asleep. Patients who consented but were excluded included 5 patients who consented and later asked to be removed from the trial and the last 4 patients enrolled in the trial who were excluded to keep the trial population at the target of 800 patients. For patients in the trial population to be included in the analysis sample, a record of their index admission had to have been found in the hospital discharge data. Further information is provided in the Supplementary Appendix.

The trial population was enrolled from June 2, 2014, through September 13, 2017. Of the 1520 patients triaged, recruiters deemed 1442 eligible for participation; 809 patients consented, and half were randomly assigned to treatment. Subsequently, 5 of the 809 patients were excluded at their request; the last 4 patients enrolled were excluded in order to reach the target trial population of 800 (Figure 1).

Data Sources

The primary data were hospital discharge data collected through March 31, 2018, from the four Camden hospital systems; these accounted for 98% of New Jersey hospital discharges of Camden residents (see the Supplementary Appendix). The discharge data contained admission and discharge dates, diagnoses, discharge destination, charges and payments received, and patients’ identifying information.

We supplemented these data with data from several other sources. The Camden Coalition Health Information Exchange database contained additional demographic information and a record of the patient’s index admission (where recruitment occurred). We matched 782 of the patients (98%) in the trial to the discharge record for their index admission; match rates were balanced between the treatment group (98.5%) and the control group (97.0%). The baseline survey provided additional socioeconomic information on patients. The Coalition recorded staff contacts with patients in the treatment group. Administrative data from the state of New Jersey provided information on social services received by trial participants (specifically, the Supplemental Nutrition Assistance Program, Temporary Assistance for Needy Families, and General Assistance), and the National Death Index provided mortality data. (See the Supplementary Appendix for additional details.)

Outcomes

The primary outcome was readmission within 180 days after hospital discharge. Secondary outcomes were the number of readmissions, the proportion of patients with two or more readmissions, hospital days, charges, payments received, and mortality — all measured 180 days after discharge — as well as readmission rates at shorter and longer time horizons. We also analyzed the primary outcome according to prespecified subgroups. With the exception of receipt of social services and mortality, all outcomes were based on hospital discharge data.

Statistical Analysis

We used linear regressions to compare outcomes for patients in the treatment and control groups. To increase precision, we included prespecified covariates for age (with patients grouped in 5-year increments), sex, indicators for non-Hispanic black and Hispanic origin, and measures of health care utilization less than 6 months and 7 to 12 months before the index admission. We also report differences in means for patients in the treatment and control groups without adjustment for covariates. We conducted a sensitivity analysis with the use of multiple imputation to account for missing outcome data for 18 patients who could not be matched to the discharge record for their index admission.33

Initially, we determined that a population of 800 would provide 80% power to detect a decrease of 9 percentage points in the 180-day readmission rate (at a two-sided significance level of 0.05). Subsequently, data from the actual study population — whose readmission rate was twice what we had assumed — indicated power to detect a decline of 9.6 percentage points in the primary outcome (see the Supplementary Appendix). There was no prespecified plan to adjust for multiple comparisons; therefore, we report P values only for the primary outcome and report 95% confidence intervals without P values for all secondary outcomes. The confidence intervals have not been adjusted for multiple comparisons, and inferences drawn from them may not be reproducible.