Thousands of patients experience difficulties in the first few days and weeks after discharge from an acute care facility and end up being re-hospitalized. A 2009 study found that 20% of Medicare patients were readmitted to hospitals within 30 days of discharge and 34% were readmitted within 90 days - at an annual cost of $17.4 billion.1 A separate federal report documented the rate of rehospitalization as 17.6% at 30 days. 2 And among 18- to 64-year-old patients in five states, the rate of rehospitalization for any reason within 6 months after discharge was 81% of the rate among patients older than 64.3
Rehospitalization after hospital discharge is a frequent adverse outcome experienced by patients with type 2 diabetes mellitus (T2DM). Patients with diabetes have an overall rehospitalization rate of 20.6%, which is 1.6 times the rate of patients without diabetes (12.5 %).4 They incur nearly twice the total inpatient costs per capita as people without diabetes.5 Examining contributing factors for early rehospitalization can guide efficient resource utilization and permit intervention to avoid hospital returns.
Risk factor identification is the first step toward preventing rehospitalization. This study sought to evaluate the association between a patient biomarker (HbA1c) and hospital readmissions for patients with T2DM within 90 days of discharge. Studies have reported associations between elevated HbA1c and length of hospital stay in diabetes patients admitted with sepsis.6 Research also has documented increased cardiovascular (CV) events7 and increased CV event risk in patients with established diabetes.8 Diabetes is a recognized predictor of adverse events after coronary artery bypass surgery.9
HbA1c is the most widely accepted outcome measure for evaluating glycemic control in patients with diabetes.10 Evaluation of HbA1c provides the most objective and reliable information about long-term metabolic control.11 The American Diabetes Association recommends an HbA1c level of less than 7%.11 The mean HbA1c value in U.S. patients with T2DM ranges from 7.8% to 8.6%, and one-third of all T2DM patients have an HbAlc value greater than 9.5%.12
Previous studies have linked elevated HbA1c to increased CV events in general7 as well as increased risk for CV events in patients with established T2DM.8,9 In patients with type 1 diabetes, HbA1c is also associated with increased risk for hospital admission.14 Halkos et al13 also linked elevated preoperative HbA1c with adverse events after coronary artery bypass surgery. HbA1c has been associated with a 36% increased risk of heart failure for every 1% rise in HbA1c in patients with a primary diagnosis of heart failure, and a 26% per 1% rise in HbA1c in patients with a secondary diagnosis of heart failure.14 A limited number of studies have evaluated whether an elevated HbA1c in patients with T2DM can be used as a risk factor predictor for rehospitalization.
In this retrospective chart review, I identified patients with T2DM as eligible for study if they had more than one hospitalization between Jan. 1, 2010, and Dec. 31, 2010. I reviewed each case to determine whether sufficient documentation of HbA1c could be retrieved. I reviewed more than 150 charts and selected only charts with complete information for specified parameters (50 charts). Patients older than 18 who had a diagnosis of T2DM and whose HbA1c was measured on the first day after admission were included. I extracted the resulting data to a spread sheet and converted it to electronic format. The variable under consideration was HbA1c, and the relationship between HbA1c values and hospital readmission was analyzed.
Sixty-four percent of the patients were older than 40, and 86% reported having a primary care provider. Fifty-two percent said they had followed up with their primary care provider after initial hospital discharge. Half the patients were readmitted less than 30 days after discharge, 22% were readmitted less than 3 months later, and 28% were readmitted within the first year of initial admission. This readmission data, which is similar to that cited at the start of the article, confirms that examining contributing factors for early re-hospitalization can guide efficient resource utilization and permit intervention to avoid hospital returns. Analysis of reasons for readmission assist in identifying targeted interventions that can result in better health outcomes.
Analysis & Results
Twelve percent of patients had an HbA1c level below 7%. Sixty-four percent had HbA1c between 7.1% and 8.4%. Twenty-four percent of patients had HbA1c over 8.5%. I used a chi square to test for statistically significant differences between dichotomous variables. I applied the Pearson chi square analysis and Nominal by Nominal Symmetric Measures to confirm the findings. I found no relationship between age and hospital readmission rate.
Of the patients whose records were studied, 74% had an HbA1c over 7% and 24% had an HbA1c above 8.5%. Cross tabulation analysis showed a relationship between hospital admission and HbA1c (chi square = 20.9, df = 6, p = .0.002). Directional measure by nominal Lambda found a significant relationship (p = 0.002). Analysis of Phi, Cramer's V contingency coefficient analysis also confirmed the stated findings.
The analysis found that high HbA1c values are associated with increased risk for rehospitalization after discharge (p = .05) and that elevated HbA1c is a strong predictor of risk for rehospitalization. Interventions targeted to patients within these parameters could produce financial benefits and improve the overall well-being of patients.
This study suggests that HbA1c is an effective way to identify patients at higher risk for hospital readmission. The financial burden of T2DM for patients, employers and insurers is high. Each stakeholder has an interest in decreasing the costs of T2DM care and reducing the negative impact of the disease on productivity and employee absenteeism.15 Identification of modifiable risk factors is the first step toward prevention of hospitalization and reduction of associated costs. Particular efforts should be made to avoid readmission. Interventions targeted to patients with the above parameters have a significant financial benefit and improve the overall well-being of patients.
The findings of this study may be helpful in designing interventions to lower HbA1c in this population. Exploring which patients have a higher probability of preventable readmissions and identifying cost-effective interventions to target them would be valuable.
Limitations of this study are its small sample size and the age of the subjects. Most patients included in the study were older than 55 and therefore did not represent the general population. Additionally, readmission rates could be secondary to multiple comorbid conditions associated with T2DM and not necessarily HbA1c.
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2. Medicare Payment Advisory Commission. A Path to Bundled Payment Around a Rehospitalization. http://www.medpac.gov/documents/Jun08_EntireReport.pdf
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13. Halkos M, et al. Elevated preoperative hemoglobin A1c level is predictive of adverse events after coronary artery bypass surgery. J Thorac Cardiovasc Surg. 2008;136(3):631-640.
14. Gerstein HC, et al. The relationship between dysglycaemia and cardiovascular and renal risk in diabetic and non-diabetic participants in the HOPE study: a prospective epidemiological analysis. Diabetologia. 2005;48(9):1749-1755.
15. Healthcare Cost and Utilization Project. Statistical brief #17: Hospital Stays Among Patients With Diabetes, 2004. http://www.medpac.gov/documents/Jun08_EntireReport.pdf
Mekonnen Kidane is a family nurse practitioner at United Health in Nashville. He has completed a disclosure statement and reports no relationships related to this article.