Readmissions by age following hospital stays with CDI

Figure 1 illustrates readmission rates by age group. Thirty-day readmissions with CDI as a principal diagnosis ranged from 2.0 percent for the youngest age group to 5.5 percent for patients 65 and older. Thirty-day readmission rates for any-listed CDI ranged from 8.3 percent for pediatric cases to 14.2 percent for patients 65 and older. All-cause 30-day readmissions showed less variation across age groups, ranging from 26.5 percent to 29.6 percent.

Figure 1

Readmissions following hospital stays associated with CDI: 30-day and 90-day readmission rates by age, 2009. Source: AHRQ, Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project, readmissions file based on the State Inpatient (more...)

Ninety-day readmissions were uniformly higher than 30-day readmissions across all age groups, with 40 percent or more in all age groups readmitted for any cause.

While both 30-day and 90-day readmission rates with a diagnosis of CDI were highest for patients older than 65 years, all-cause readmissions were similar for patients ages 45–64 and 65 plus.

Readmissions by sex following hospital stays with CDI

Figure 2 illustrates that readmission rates for males and females were comparable for most types of readmissions (less than 7 percent differences between males and females for both 30- and 90-day all-cause readmissions for all-listed CDI and all-cause readmissions). For readmissions with CDI as the principal diagnoses, rates were 20–25 percent higher for females.

Figure 2

Readmissions following hospital stays associated with CDI: 30-day and 90-day readmission rates by sex, 2009. Source: AHRQ, Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project, readmissions file based on the State Inpatient (more...)

Readmissions by primary expected payer following hospital stays with CDI

Figure 3 illustrates readmission rates by payer and shows that the 30-day readmission rate with CDI as the principal diagnosis was about 50 percent higher for patients covered by Medicare (5.3 percent) than for all other payers (3.5–3.6 percent).

Figure 3

Readmissions following hospital stays associated with CDI: 30-day and 90-day readmission rates by payer, 2009. Source: AHRQ, Center for Delivery, Organization, and Markets, Healthcare Cost and Utilization Project, readmissions file based on the State (more...)

The 30-day readmission rate with CDI as any-listed diagnosis was lowest for uninsured patients (7.2 percent) and nearly twice as high for Medicare-covered patients (14.1 percent). Nearly 11 percent of Medicaid-covered patients and 9.4 percent of privately insured patients were readmitted with CDI within 30 days. Ninety-day readmission rates with CDI as a principal diagnosis and any-listed CDI showed a similar pattern.

However, all-cause readmission rates were two to three times higher than readmissions with CDI at both 30 and 90 days. Within 30 days following discharge with CDI, 32.7 of Medicaid-covered patients were readmitted to the hospital for any cause and within 90 days, 48.6 percent of patients covered by Medicaid were readmitted for any cause. These readmission rates were similar to those for Medicare. All-cause readmission rates for Medicare- and Medicaid-covered patients were 30–50 percent higher than for privately insured and uninsured patients at both 30 and 90 days.

Readmissions among patients discharged to long term care following hospital stays associated with CDI

Table 2 provides information on readmissions for the subset of patients discharged to long term care (LTC) after an index stay that involved CDI. Overall, 41.5 percent of index stays were discharged to long term care. For most types of readmissions, readmission rates for patients discharged to LTC were somewhat higher than for patients overall. For example, 14.0 percent of patients discharged to LTC were readmitted within 30 days with any-listed diagnosis of CDI, compared to 12.8 percent overall (see Table 1). However, readmission rates among patients discharged to LTC were lower for CDI as the principal diagnosis (e.g., 3.8 percent of LTC patients were readmitted for CDI as the principal diagnosis, compared to 4.8 percent overall [see Table 1]). Most striking was the all-cause readmission rate for long term care patients—nearly half (49.0 percent) were readmitted within 90 days.

Table 2

Readmissions following index hospital stays associated with CDI for patients discharged to long term care (LTC) after their index stay, 2009.

Reasons for readmissions

Table 3 provides information on the principal diagnoses for readmissions following an index stay that involved CDI. Among patients with a diagnosis of CDI on readmission, over a third of readmitted patients have a diagnosis of CDI as the principal diagnosis for both 30-day and 90-day readmissions. Other infection-related diagnoses predominate—septicemia, pneumonia, and UTI. Other conditions reflect serious complications or comorbidities—CHF, complication of medical care, respiratory failure, aspiration pneumonitis, and renal failure. A similar pattern was seen for patients discharged to long term care following their index stay (data not shown).

Table 3

Top 10 principal diagnoses for readmissions following a CDI index stay, 2009.

Diagnoses, ICD-9-CM, and Clinical Classifications Software (CCS)

The principal diagnosis is that condition established after study to be chiefly responsible for the patient’s admission to the hospital. Secondary diagnoses are concomitant conditions that coexist at the time of admission or that develop during the stay. For this study, all-listed diagnoses were used (principal and secondary diagnoses).

ICD-9-CM is the International Classification of Diseases, Ninth Revision, Clinical Modification, which assigns numeric codes to diagnoses. There are about 14,000 ICD-9-CM diagnosis codes.

CCS categorizes ICD-9-CM diagnoses into a manageable number of clinically meaningful categories¹² This “clinical grouper” makes it easier to quickly understand patterns of diagnoses. CCS categories identified as “Other” are typically not reported; these categories include miscellaneous, otherwise unclassifiable diagnoses that may be difficult to interpret as a group.

Case definition

The ICD-9-CM codes defining Clostridium difficile infections (CDI) include the following diagnosis code: 008.45.

Readmission

The 30-day (90-day) readmission rate is defined as the number of admissions for which there was at least one subsequent hospital admission within 30 (90) days divided by the total number of admissions between January and November 2009 (January and September 2009). That is, when a patient is discharged from the hospital, they are followed for 30 (90) days in the data. If any readmission to the same or different hospital occurs during this time period, the admission is counted as having a readmission. No more than one readmission is counted within the 30 (90) day period since the outcome measure assessed here is “percentage of admissions who are readmitted.” If a patient was transferred to a different hospital on the same day or was transferred within the same hospital, the two events were combined as a single stay and the second event was not counted as a readmission. That is, transfers were not considered a readmission. In the case of admissions for which there was more than one readmission in the 30 (90) day period, the data presented in this Statistical Brief reflect the characteristics of the first readmission.

Every qualifying hospital stay with the specified procedure is counted as a separate index (starting point) admission. Thus a single patient can be counted multiple times during the course of the January to November (January to September) observation period. In addition, index admissions do not require a prior “clean period” with no hospitalizations; that is, a hospital stay may be both a readmission for a prior stay and the index admission for a subsequent readmission. Admissions were disqualified from the analysis as index admissions if they could not be followed for 30 (90) days for one of the following reasons: (1) admissions in which the patient died in the hospital, (2) admissions missing information on length of stay, and (3) admissions discharged in December (September to December) of 2009.

Costs and charges

Total hospital charges were converted to costs using HCUP Cost-to-Charge Ratios based on hospital accounting reports from the Centers for Medicare & Medicaid Services (CMS).¹³Costs will reflect the actual expenses incurred in the production of hospital services, such as wages, supplies, and utility costs; charges represent the amount a hospital billed for the case. For each hospital, a hospital-wide cost-to-charge ratio is used. Hospital charges reflect the amount the hospital billed for the entire hospital stay and do not include professional (physician) fees. For the purposes of this Statistical Brief, costs are reported to the nearest hundred.

Mean cost per day is calculated as the mean cost per stay divided by the mean length of stay.

Payer

Payer is the expected primary payer for the hospital stay. To make coding uniform across all HCUP data sources, payer combines detailed categories into more general groups:

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Medicare: includes fee-for-service and managed care Medicare patients

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Medicaid: includes fee-for-service and managed care Medicaid patients. Patients covered by the State Children’s Health Insurance Program (SCHIP) may be included here. Because most State data do not identify SCHIP patients specifically, it is not possible to present this information separately.

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Private Insurance: includes Blue Cross, commercial carriers, and private HMOs and PPOs

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Other: includes Worker’s Compensation, TRICARE/CHAMPUS, CHAMPVA, Title V, and other government programs

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Uninsured: includes an insurance status of “self-pay” and “no charge.”

When more than one payer is listed for a hospital discharge, the first-listed payer is used.

Discharge status

Discharge status indicates the disposition of the patient at discharge from the hospital and includes the following six categories: routine (to home); transfer to another short-term hospital; other transfers (including skilled nursing facility, intermediate care, and another type of facility such as a nursing home); home health care; against medical advice (AMA); or died in the hospital.