1. Elizabeth McCullough, 3M Health Information Systems
Potentially Preventable Readmissions: Overview of Definitions and Clinical Logic HSCRC April 6, 2010
PPRs were constructed as a categorical model using an approach of iterative sequential hypothesis testing by panels of clinical experts with repetitive data verification.
Elizabeth McCullough, 3M Health Information Systems
6 April 2010

2. PPR-Potentially Preventable Readmissions
PPR Definition:
A Potentially Preventable Readmission (PPR) is a readmission that is clinically-related to the initial hospital admission that may have resulted from a deficiency in the process of care and treatment or lack of post discharge follow-up rather than
unrelated events that occur post discharge (broken leg due to trauma), or
readmissions that were planned at the time of the discharge from the initial admission.
Clinically-related:
Clinically-related is defined as a requirement that the underlying reason for following a prior hospital readmission be plausibly related to the care rendered during or immediately following a prior hospital admission.

3. Why PPRs What might cause a PPR to happen?
A readmission is considered to be clinically related to a prior admission and potentially preventable if there was a reasonable expectation that it could have been prevented by one or more of the following:
The provision of quality care in the initial hospitalization
Adequate discharge planning
Adequate post-discharge follow up
Improved coordination between inpatient and outpatient Health Care Teams
**Identifying Potential Preventable Readmission Article, Health Care Financing Review Fall 2008

4. The Identification of Potentially Preventable Readmissions (PPRs)
Three Phases
Phase I: Identify Excluded Admissions and Non Events
Phase II: Determine Preliminary Classification of Remaining Admissions
Phase III: Identify PPRs and Determine Final Classification of Admissions
Define exclusion criteria for identifying initial admissions for which a subsequent readmission is excluded from consideration as a PPR (e.g. discharged against medical advice)

5. Phase I :Identify Excluded Admissions and Non-events

6. Exclusions from the readmission methodology
No possible clinical relation to the index admission (cholecsytectomy two weeks after total hip replacement);
Not clearly related to improvement opportunities in either hospital or outpatient care (e.g. readmissions for malignancy care or a motor vehicle accident)
If any of the following conditions apply to the initial admission, a subsequent readmission is globally excluded from consideration as a PPR
Admissions for which follow-up care is intrinsically extensive and complex
Major or metastatic malignancies treated medically
Multiple trauma, burns
Discharge status indicates limited hospital & provider control
Left against medical advice
Transferred to another acute care hospital
Neonates
Other exclusions
Specific eye procedures and infections
Cystic fibrosis with pulmonary diagnoses
Died – not included as candidate initial admissions (denominator)
PPR Definition Manual Appendix E for List of Globally Excluded APR DRGs
PPR Definition Manual Appendix G for List of Major and Metastatic Malignant Diagnoses
Several kinds of admissions are not considered preventable and therefore can be classified neither as either a PPR nor an Initial Admission. Major or metatastic malignancies, multiple traumas, and burns are not considered preventable and are globally excluded because the follow-up care is intrinsically clinically-complex and extensive. Further, ICD-9-CM may lack the clinical detail necessary to determine if an admission is potentially preventable (e.g. stage of a malignancy). Neonatal discharges have unique attributes. Admissions related to eye care and cystic fibrosis are globally excluded for similar reasons. Readmissions with a discharge status of “left against medical advice” are globally excluded because,
under these circumstances, the hospital has limited influence on the care rendered to the patient.

7. Non Event Admissions
Admissions for certain non-acute care services during the interval between a prior admission and subsequent admission do not affect the classification of the subsequent admission
List of Non Event APR DRGs
860 Rehabilitiation,
862 Other Aftercare & Convalescense,
863 Neonatal Aftercare
List of Non Event Discharge Status Codes
Admissions for certain non-acute care services during the interval between a prior admission and subsequent admission do not affect the classification of the subsequent admission. These admissions are called Non-events because they are ignored when determining eligibility based on the readmission time interval.
Admissions with an APR DRG of rehabilitation, aftercare, or convalescence are classified as Non-events. For the full list of Non-events, see Appendix F. Admissions to non-acute care facilities including rehabilitation, hospice, long-term care, skilled nursing facilities, intermediate care facilities, or other convalesce-type facilities are considered Non-events. Further, same-day transfers within or across acute
care hospitals identified by the patient discharge status types listed in Appendix F are considered Non-events.

8. Phase II: Determine Preliminary Classification of Remaining Admissions

9. Example Readmission
In the following example, patient 2C was discharged home from an acute care hospital on January 1st and admitted back into the hospital January 5th. The time interval between the first admission and the subsequent admission is four days. Since it is within the fifteen day readmission time interval, the second admission is therefore preliminarily classified as a readmission. The first admission that is followed by a subsequent admission within the readmission time interval is preliminarily classified as an Initial Admission. For example, since there is a subsequent readmission four days following discharge from the first admission, the first admission for patient 2C in the following figure is classified as an Initial Admission
In the next example of patient 2A, since the time interval between the first and second admission is three days and the time interval between the second and third admission is fourteen days, the second and third admissions are preliminarily
classified as readmissions.
However, for patient 2D the time interval between the second and third admissions is twenty days, which is five days outside the readmission time interval. So the third admission is not preliminarily classified as a readmission.

10. Examples of a Non Events Admissions that get “ignored”
Admissions for certain non-acute care services during the interval between a prior admission and subsequent admission do not affect the classification of the subsequent admission. These admissions are called Non-events because they are ignored when determining eligibility based on the readmission time interval.
Admissions with an APR DRG of rehabilitation, aftercare, or convalescence are classified as Non-events. For the full list of Non-events, see Appendix F. Admissions to non-acute care facilities including rehabilitation, hospice, long-term care, skilled nursing facilities, intermediate care facilities, or other convalesce-type facilities are considered Non-events. Further, same-day transfers within or across acute
care hospitals identified by the patient discharge status types listed in Appendix F are considered Non-events.
In this example, patient 2B was first hospitalized for respiratory failure (APR DRG 133). Patient 2B was discharged home and then readmitted to the hospital three days later for rehabilitation (APR DRG 860). After four days of rehabilitation, patient 2B was discharged home again but then readmitted back to the hospital for COPD (APR DRG 140) seven days later. Because the second admission was for rehabilitation, it is classified as a Non-event in phase I of the PPR logic, and therefore does not impact the calculation of the number of days between admissions. So in this case, the number of days between the third admission for COPD and the first admission for respiratory failure is fourteen days.

11. Transfer Example Transfer To Another facility:
Transferred from To Another facility:
Even if the subsequent admission is later transferred to another acute care hospital based on the discharge status, the subsequent admission is preliminarily classified as a readmission. For example, patient 2E is readmitted back to the hospital three days after the first admission. During the second admission, patient 2E is transferred to another acute care hospital. Since the time interval between the first and second admission is three days, the second admission is preliminarily classified as a readmission even though the patient was transferred.
However, if a patient is transferred to another acute care hospital, the admission to the receiving hospital is not considered a readmission. For example, patient 2F is first admitted to a hospital and then transferred to another acute care hospital. Since it is a continuation of the first admission, the second “transfer to” admission is not classified as a readmission.
Patient 2J is first admitted to a hospital and later transferred to another acute care hospital. Patient 2J is discharged home from the second admission (the transfer to hospitalization) and then readmitted to the hospital fourteen days later for a third admission. Because the patient was transferred from another acute care hospital to continue the care required from the first admission, the second admission cannot be considered a readmission. However, the second admission is
preliminarily classified as an Initial Admission, and, since the number of days between the second and third admission is less then fifteen days, the third admission is preliminarily classified as a readmission.

12. Excluded and Only Admissions Example
If a patient has only a single admission, it is classified as an Only Admission. For example, patient 2L has only one admission (i.e. no subsequent admissions) and is classified as Only Admissions.
Subsequent admissions within the readmission time interval that follow an Excluded Admission are not classified as a readmissions. For example, patient 2G is first admitted to the hospital for Craniotomy for Trauma (APR DRG 20) and then three days after discharge readmitted back to the hospital for heart failure (APR DRG 194). The first admission is classified as an Excluded Admission. Therefore, the second admission for heart failure cannot be classified as a readmission even if the number of days between the admissions is within the readmission time interval.
If the number of days between a subsequent admission and the prior admission is greater than the specified readmission time interval, and the subsequent admission is not followed by a second admission within the readmission time interval, both admissions are preliminarily classified as Only Admissions. For example, Patient 2M has two admissions with thirty-two days between the discharge date from the first admission and the admit date of the second admission. In this case, both admissions are classified as Only Admissions.

13. Phase III: Identify PPRs and Determine Final Classification of Admissions
Develop criteria for determining if a readmission is potentially preventable (i.e. a PPR). In the construction of the PPRs, the physician panel considered a readmission clinically related to a prior admission and potentially preventable if the reason for the readmission falls into one of three categories for medical readmissions and one of two categories for surgical readmissions. Readmissions for medical reasons are much more common than readmissions for surgical procedures, regardless of the reason for the initial admission.
Admissions that are preliminarily classified as readmissions at the completion of phase II, are only considered PPRs if there is a clinical relationship between the readmission and the Initial Admission. Readmissions that are not clinically-related are re-classified as either Initial Admissions, Only Admissions, or Transfer Admissions.

14. Clinically Related Medical Readmissions
Medical readmission for a continuation or recurrence of the reason for the initial admission, or for a closely related condition.
Medical readmission for an acute decompensation of a chronic problem that was not the principal reason for the initial admission, but may be related to care either during or after the initial admission.
Medical readmission for an acute medical condition or complication that may be related to or may have resulted from care during the initial admission or in the post-discharge period after the initial admission.
The three categories of clinically related medical readmissions are as follows:
Reason 1 The most common example of this type of readmission is a patient discharged from and admission for Congestive Heart Failure who is then readmitted for the same reason
Reason 2 Such readmissions could be triggered by failure to renew lapsed prescriptions or incomplete instruction about returning to a previous medical regimen at the time of discharge, miscommunication about changes in a regimen that could affect an underlying chronic condition, lack of prompt follow-up by a primary care team, or failure to communicate in-hospital events, changes in the medical regimen, and issues that require ongoing monitoring to the primary care provider.
Reason 3 Examples: Patients discharged after elective surgery readmitted with a urinary tract infection likely related to an indwelling foley catheter during the initial admission; or readmitted with a post-operative wound infection

15. Clinically Related Surgical Readmissions
Readmission for a surgical procedure to address a continuation or a recurrence of the problem causing the initial admission.
Readmission for surgical procedure to address a complication that may be related to or may have resulted from care during the initial admission.
The two categories of clinically related surgical readmissions are as follows:
Reason 1 Examples: Patients discharged after coronary angioplasty then readmitted for coronary bypass grafts (CABG); patients discharged after an admission for unexplained abdominal pain readmitted to undergo an appendectomy
Reason 2 Example: Patients readmitted for extensive surgical debridement for a post-operative wound infection

16. Methodology for Selecting Potentially Preventable Readmissions (PPRs)
The PPR logic creates a matrix in which there are 314 rows representing each possible base APR DRG of the Initial Admission, and 314 columns representing each possible base APR DRG of the readmission. Each cell in the matrix represents a unique combination of a specific type of Initial Admission and readmission. The end result is that each of the 98,596 cells contain a specification of whether the combination of the base APR DRG
for the Initial Admission and the readmission is clinically-related pair and therefore potentially preventable. This matrix operationalizes the definition of “clinically-related” in the PPR logic. Appendix M contains a list of each APR DRG for the
Initial Admission, followed by the clinically-related readmission APR DRGs. For example, the APR DRG 21 “Craniotomy Except for Trauma” lists several clinically-related APR DRGs, such as APR DRG 53 “Seizure.” A readmission assigned to APR DRG 53 “Seizure” would be determined to be clinically-related to an Initial Admission assigned to APR DRG 21 “Craniotomy Except for Trauma,” thereby making the readmission a PPR.

17. PPR Matrix v27
98,596 cells in 314 Initial Admission (IA) APR DRG x 314 Readmission (RA) APR DRG Matrix
22% clinically related IA by RA APR DRG combination
37% globally excluded IA by RA APR DRG combination
41% DRG specific clinical exclusion IA by RA APR DRG combination

19. Phase III- Identify PPRs and Determine Final Classification of Admission
A readmission chain is a sequence of PPRs that are all clinically-related to the Initial Admission and that initiated the readmission chain. A readmission chain contains an Initial Admission and at least one PPR that is clinically-related to the
Initial Admission. The first admission for pulmonary edema (APR DRG 133) is classified as an Initial Admission because it is followed by a clinically-related admission of “Other Pneumonia” (APR DRG 139), within the readmission time window. The combination of an Initial Admission (admission 1) and a PPR (admission 2) starts a readmission chain. Since it is clinically-related to the Initial Admission for pulmonary edema and is within the readmission time window of the previous admission 2, the third admission for COPD (APR DRG 140) seven days after being discharged home from the second admission is also classified as a PPR. Therefore, admission 3 extends the readmission chain to include 2 PPRs.
If a sequence of PPRs has already been started, a subsequent admission may continue the chain: if the readmission falls within the readmission time interval; and the readmission chain is clinically-related to the Initial Admission that started the readmission chain. If the readmission following an established readmission chain is determined not to be clinically-related to the Initial Admission of the chain, the readmission chain is terminated. If a readmission chain is not already established, the readmission may be the first readmission in the chain if the readmission clinically-relates to the prior admission.
13. Identify Readmission Chains
A readmission chain is a sequence of PPRs that are all clinically related to the Initial Admission that initiated the readmission chain. Therefore, a readmission chain contains an Initial Admission and at least one, and possibly multiple, PPRs that are all clinically related to the Initial Admission. An example of this is seen in patient 3B. The first admission for pulmonary edema, APR DRG 133, is classified as an Initial Admission because it is followed by a clinically related admission of other pneumonia, APR DRG 139, within the readmission time window. The combination of an initial admission (admission 1) and a PPR (admission 2) starts a readmission chain. The third admission for COPD, APR DRG 140, seven days after being discharged home from the second admission is also classified as a PPR since it is clinically related to the initial admission for pulmonary edema and is within the readmission time window of the previous admission 2. Therefore, admission 3 extends the readmission chain to include 2 PPRs.
If a sequence of PPRs has already been started, then a subsequent admission may continue the chain if the readmission falls within the readmission time interval and is clinically related to the Initial Admission that started the readmission chain. If the readmission following an established readmission chain is determined not to be clinically related to the Initial Admission of the chain, then the readmission chain is terminated. If a readmission chain is not already established, then the readmission may be the first readmission in the chain if the readmission clinically relates to the prior admission. 19

20. Phase III- Identify PPRs and Determine Final Classification of Admission
Determine if a Readmission Chain is Terminated
Reasons for terminating a readmission chain
Admissions with a discharge status of “died”
Still classified as PPR, but PPR terminates the readmission chain
Excluded admissions
Any subsequent admission may be classified as an initial admission and start a new chain
Transfers to another acute care facility
Considered a PPR
Transfer readmission will terminate the readmission chain and no subsequent admission will be part of the readmission chain
14. Determine if a Readmission Chain is Terminated
There are several reasons for terminating a readmission chain Terminating the chain prevents any subsequent readmissions from joining the chain. They include:
Admissions with a discharge status of “died”
Excluded admissions
Transfers to another acute care facility
PPRs resulting in the discharge status of “died” are also still classified as PPRs, but the PPR terminates the readmission chain. Excluded Admissions also terminate the readmission chain and any subsequent admission may be classified as an Initial Admission and start a new chain. Lastly, PPRs resulting in the patient being transferred to another acute care facility are considered a PPR. However, a transfer readmission will also terminate the readmission chain and no subsequent admission will be part of the readmission chain. 20

21. Phase III- Identify PPRs and Determine Final Classification of Admission
Re-classify Readmission when not Clinically Related to Initial Admission
15. Re-classify Readmission when not Clinically Related to Initial Admission
Admissions preliminarily classified as readmissions that are not clinically related to the Initial Admission in steps are re-classified as either Initial Admissions, Transfer Admissions or Only Admissions. Readmissions are re-classified as Transfer Admissions for discharge status of transfer to another acute care hospital. For example, the second admission for Patient 3C in the diagram below is within the readmission time interval, however the readmissions is not clinically related to admissions 1 so it is re-classified as a Transfer Admission. Otherwise, readmissions are re-classified as an Initial Admission if there is a subsequent clinically related PPR within the readmission time interval. This is illustrated in the example of Patient 3D. In addition, readmissions are re-classified as an Only Admission if there is not a subsequent clinically related PPR within the readmission time interval as shown in the example with Patient 3E. 21

22. Phase III- Identify PPRs and Determine Final Classification of Admission
Re-classify Initial Admission when Readmission not Clinically Related
16. Re-classify Initial Admission when Readmission not Clinically Related
Initial Admissions where there are no subsequent clinically related PPRs are re-classified as Only Admissions. For example, the readmission for Appendectomy, APR DRG 225, is not clinically related to the Initial Admission of Bronchiolitis, APR DRG 138, therefore, the Initial Admission is re-classified as an Only Admission. 22

23. Reasons for Readmission Florida, All Patients, 2004-2005
Reason Description
Count
Percent 1
Medical – continuation of initial problem
57,515
24.7 2A
Medical – decompensation of chronic problem (ambulatory care sensitive condition)
39,736
17.1 2B
Medical – other decompensation
18,164
7.8 3
Medical – complication of previous admission
76,361
32.8 4
Surgical – continuation of initial problem
8,217
3.5 5
Surgical – complication of initial admission
6,532
2.8 6A
Mental health, non-MH initial admission
6,325
2.7 6B
Substance abuse, non SA initial admission
1,496
0.6 6C
Mental health or substance abuse readmission, initial admission for MH or SA
18,704
8.0
Total
233,050
100.0

24. Top 15 Initial Admissions followed by one or more PPR - 2007
Top 15 represents 35% of all initial admissions followed by PPRs 24 24

25. Top 15 Reasons for PPRs
Top 15 PPRs represents 42% of charges on PPRs for a 30 day readmission time window 25 25

26. Top Five PPR Reasons for an Initial Admission of Heart Failure - 200726 26

27. Summary of PPRs
Determines if there is a probable clinical relationship between an initial hospitalization and a readmission
Identify admissions that are potentially preventable
Identify admissions that are “at risk” for being followed by a potentially preventable readmission
Identify chains of readmissions that are all related to the same prior admission
Determine numerator and denominator for computing readmission rates (dependent variable)