Examining Post Acute Care Relationships in an Integrated Hospital System. 3.9 Multivariate analysis results

02/01/2009

The regression models presented here provide more information on the factors that affect (1) 78 index admission length of stay; (2) use of any PAC services; (3) first site of PAC, (4) readmission to acute hospitals during PAC episodes; and (5) total episode payments. These five models were run using three sets of independent variables. The key differences between these sets of independent variables were the severity measures. In our previous ASPE analyses using the 2005 Medicare claims data, we used the APR-DRG severity measures and these variables were included in one of the sets of independent variables presented here (Set 1). In our work using the 2006 Medicare claims data, we moved to using the MS-DRG severity measures given that CMS policy has adopted the use of MS-DRGs as of FY 2008. The MS-DRGs were included in place of the APR-DRG severity of illness variables in the second set of independent variables (Set 2). MS-DRGs have fewer categories differentiating severity of illness, and for that reason, the third set of independent variables we used included both MS-DRG severity levels and HCCs (Set 3). The HCC variables indicate the presence of the 11 most common comorbid conditions that were present in at least 5.0 percent of the study sample. The adjusted R2, measuring the degree to which the independent variables predict the dependent variable, increased notably with the addition of the 11 HCC variables, indicating the usefulness of the HCCs in addition to the MS-DRGs in predicting the outcome variables. The adjusted R2 in the models predicting total episode payment was 0.1319 in the models using the APR-DRG severity measures, the adjusted R2 decreased to 0.0689 in the models using the MS-DRG, and the adjusted R2 increased to 0.2804 when using both the MS-DRG and the HCC indicator variables. The HCCs provide an opportunity to learn more about the effects of comorbid conditions on the dependent variables of interest.

The results of the regression models are presented in Table 3-24, Table 3-25, and Table 3-26. These three tables contain the regression models predicting index acute admission length of stay, any PAC use, and first site of PAC care for the three sets of independent variables (Sets 1, 2, and 3, respectively). Table 3-27 contains the results for the models predicting readmission during PAC episodes and episode payment for each of the three sets of independent variables.

The results of the binomial and multinomial logits are presented as odds ratios. Values < 1 indicate a negative association; values >1 indicate a positive association. Exponentiated coefficients from the multinomial logistic regression are relative risk ratios. They identify the proportional change in the risk (probability) of discharge to each PAC setting relative to the risk of discharge to hospital outpatient therapy, which is associated with a one-unit change in the explanatory variable. Values < 1 indicate an associated risk reduction. The binomial results represent the average effects across PAC sites while the multinomial model presents the odds of using a particular type of service relative to the odds of using hospital outpatient therapy. This is useful for examining the magnitude of the differences in the probability of admission to one site versus another compared to the average case with a particular beneficiary or market characteristic. The coefficients reported for the ordinary least squares (OLS) model predicting index admission length of stay and episode payments reflect the increase in index admission days and payments for a one-unit change in the independent variable. Positive coefficient values indicate an increase in length of stay or episode payment with increasing values of the independent variable.

Table 3-24. Regression Results Predicting Index Admission Length of Stay, Any PAC Use, and First Discharge Destination Using Independent Variable Set 1 (APR-DRGs), 2006
  OLS Regression
Predicting Index Acute Admission LOS
Binomial Logit1
Predicting PAC/NoPAC
Multinomial Logit: Predicting Discharge Destination2
Variable Coefficient3 Odds Ratio3 Home Health
Odds Ratio3
IRF
Odds Ratio3
LTCH
Odds Ratio3
SNF
Odds Ratio3

1. Note that the reference group for the binomial logit is No PAC Use.
2. Note that the reference group for the multinomial logit is Hospital Outpatient Therapy.
3. Significance * p<0.05. ** p<0.01, *** p<0.0001.
4. The reference group for age is <65.
5. The reference group includes White, Asian, Hispanic, North American Native, Unknown, and Other.
6. The reference group for APR-DRG Severity Index is minor.
7. The reference group for the census division variables is New England.
8. The reference group for each of these variables is the absence of this type of organizational relationship.
9. The reference group is rural location.
10. The reference group is for-profit.
11. The reference group for each of these variables is the absence of this DRG as the index acute admission DRG.

SOURCE: RTI analysis of 2006 Medicare claims 5% sample.

Intercept 2.415***          
Demographics Female 0.028 1.314*** 1.183*** 1.282*** 1.060 1.431***
Any Medicaid in 2005 0.253*** 1.415*** 0.682*** 0.602*** 0.988 1.333***
Age 65-744 0.026 1.645*** 1.160** 1.093 0.799** 1.410***
Age 75-84 0.177*** 2.834*** 1.449*** 1.676*** 1.078 3.248***
Ages 85 + 0.083** 5.052*** 1.247*** 1.317*** 0.885 4.859***
Black5 0.368*** 0.977 1.123** 0.978 1.458*** 0.924
Severity APR-DRG Severity Index = moderate6 1.298*** 1.776*** 1.272*** 1.515*** 1.804*** 1.869***
APR-DRG Severity Index = major 3.966*** 3.282*** 1.710*** 2.376*** 3.261*** 3.226***
APR-DRG Severity Index = extreme 12.061*** 7.712*** 1.691*** 4.775*** 5.223*** 6.376***
Supply IRF beds/1,000 beneficiaries/state -0.050 1.021 0.752*** 1.905*** 0.795** 0.718***
SNF beds/1,000 beneficiaries/state -0.001 1.000 0.975*** 0.987*** 0.998*** 0.999
LTCH beds/1,000 beneficiaries/state -0.022 1.045*** 1.333*** 1.057 1.162*** 1.146***
Census Division7 Middle Atlantic 0.666*** 0.826*** 1.069 1.104 0.991 0.845*
East North Central -0.318*** 0.645*** 0.629*** 0.620*** 1.000 0.619***
West North Central -0.257*** 0.544*** 0.458*** 0.364*** 0.651* 0.361***
South Atlantic -0.053 0.623*** 0.710*** 0.738** 0.676* 0.634***
East South Central -0.085 0.538*** 0.603*** 0.799* 0.931 0.550***
West South Central 0.009 0.462*** 0.828* 0.800* 2.253*** 0.306***
Mountain -0.390*** 0.548*** 0.602*** 0.821 1.378 0.648***
Pacific -0.132* 0.426*** 0.720*** 0.814 1.449* 0.437***
Organizational Relationships of Discharging Acute Hospital8 Any Colocated Provider 0.014 1.009 - - - -
Any Subprovider 0.137*** 1.008 - - - -
Any Subprovider IRF - - 1.044 1.917*** 0.874* 0.815***
Any Subprovider SNF - - 0.940* 0.764*** 0.780*** 1.183***
Any Subprovider HHA - - 1.001 0.945 0.812** 1.052*
Any Colocated IRF - - 1.275** 2.265*** 0.845 0.895
Any Colocated SNF - - 1.085* 1.022 0.988 1.142**
Any Colocated HHA - - 0.884* 0.797** 0.927 0.848**
Any Colocated LTCH - - 0.885** 0.934 1.512*** 0.742***
Characteristics of Discharging Acute Hospital Number of Beds 0.000*** 1.000 - - - -
Urban Location9 0.346*** 1.166*** - - - -
Not-for-profit10 -0.031 1.006 - - - -
Government run10 0.079* 0.962* - - - -
Acute DRG11 DRG 209 Major Joint & Limb Reattachment Procedures of Lower Extremity -0.239*** 25.189*** 1.277*** 4.411*** 0.401*** 1.953***
DRG 089 Simple Pneumonia & Pleurisy Age >17 w CC -0.244*** 0.959* 0.711*** 0.189*** 0.375*** 0.692***
DRG 014 Specific Cerebrovascular Disorders Except TIA 0.051 4.008*** 0.562*** 6.086 1.211 1.002
DRG 127 Heart Failure & Shock -0.199*** 1.002 1.366*** 0.297** 0.582 0.849**
DRG 210 Hip & Femur Procedures Except Major Joint Age >17 w CC 0.814*** 15.395*** 0.644** 13.204*** 2.489*** 5.155***

 

Table 3-25. Regression Results Predicting Index Admission Length of Stay, Any PAC Use, and First Discharge Destination Using Independent Variable Set 2 (MS-DRGs), 2006
  OLS Regression
Predicting Index Acute Admission LOS
Binomial Logit1
Predicting PAC/NoPAC
Multinomial Logit: Predicting Discharge Destination2
Variable Coefficient3 Odds Ratio3 Home Health
Odds Ratio3
IRF
Odds Ratio3
LTCH
Odds Ratio3
SNF
Odds Ratio3

1. Note that the reference group for the binomial logit is No PAC Use.
2. Note that the reference group for the multinomial logit is Outpatient Therapy.
3. Significance * p<0.05. ** p<0.01, *** p<0.0001.
4. The reference group for age is <65.
5. The reference group includes White, Asian, Hispanic, North American Native, Unknown, and Other.
6. The reference group for MS-DRG Severity Index No CCs.
7. The reference group for the census division variables is New England.
8. The reference group for each of these variables is the absence of this type of organizational relationship.
9. The reference group is rural location.
10. The reference group is for-profit.
11. The reference group for each of these variables is the absence of this DRG as the index acute admission DRG.

SOURCE: RTI analysis of 2006 Medicare claims 5% sample.

Intercept 3.029***          
Demographics Female -0.071*** 1.283*** 1.161*** 1.246*** 0.903* 1.375***
Any Medicaid in 2005 0.374*** 1.458*** 0.684*** 0.598*** 0.988 1.340***
Age 65-744 0.069* 1.636*** 1.155** 1.105 0.782** 1.413***
Age 75-84 0.362*** 2.916*** 1.443*** 1.692*** 0.999 3.283***
Ages 85 + 0.400*** 5.351*** 1.252*** 1.313*** 0.785** 4.949***
Black5 0.314*** 0.979 1.128** 0.977 1.489*** 0.923*
Severity6 MS-DRG Severity Index = CC 1.828*** 1.677*** 1.437*** 1.485*** 1.236** 1.610***
MS-DRG Severity Index = MCC 4.803*** 2.659*** 1.296*** 1.942*** 3.695*** 2.212***
Supply IRF beds/1,000 beneficiaries/state -0.075 1.014 0.743*** 1.883*** 1.437** 0.790***
SNF beds/1,000 beneficiaries/state -0.001 1.000 0.974*** 0.987*** 0.979*** 0.998
LTCH beds/1,000 beneficiaries/state -0.034 1.039*** 1.331*** 1.049 1.754*** 1.151***
Census Division7 Middle Atlantic 0.651*** 0.828*** 1.069 1.111 0.977 0.841*
East North Central -0.218*** 0.670*** 0.637*** 0.644*** 1.064 0.631***
West North Central -0.237** 0.560*** 0.459*** 0.370*** 0.684 0.362***
South Atlantic 0.040 0.645*** 0.706*** 0.742** 0.712* 0.638***
East South Central -0.045 0.553*** 0.609*** 0.816* 1.009 0.559***
West South Central 0.095 0.480*** 0.824* 0.796* 2.263*** 0.302***
Mountain -0.344*** 0.567*** 0.601*** 0.828 1.432 0.654***
Pacific -0.159* 0.433*** 0.714*** 0.814 1.515* 0.436***
Organizational Relationships of Discharging Acute Hospital8 Any Colocated Provider 0.004 1.008 - - - -
Any Subprovider 0.144*** 1.007 - - - -
Any Subprovider IRF - - 1.043 1.926*** 0.909 0.824***
Any Subprovider SNF - - 0.953 0.774*** 0.800*** 1.191***
Any Subprovider HHA - - 0.996 0.937** 0.779*** 1.047
Any Colocated IRF - - 1.264* 2.339*** 0.888 0.930
Any Colocated SNF - - 1.071* 1.003 0.977 1.128**
Any Colocated HHA - - 0.888* 0.803** 0.927 0.860**
Any Colocated LTCH - - 0.870** 0.925 1.588*** 0.743***
Characteristics of Discharging Acute Hospital Number of Beds 0.001*** 1.000 - - - -
Urban Location9 0.468*** 1.200*** - - - -
Not-for-profit10 0.008 1.020 - - - -
Government run10 0.096** 0.965* - - - -
Acute DRG11 DRG 209 Major Joint & Limb Reattachment Procedures of Lower Extremity 0.179*** 25.909*** 1.314*** 4.340*** 0.248*** 1.955***
DRG 089 Simple Pneumonia & Pleurisy Age >17 w CC -0.464*** 0.920*** 0.675*** 0.181*** 0.361*** 0.668***
DRG 014 Specific Cerebrovascular Disorders Except TIA -0.290*** 3.629*** 0.519*** 5.459 0.884 0.892*
DRG 127 Heart Failure & Shock -1.050*** 0.836*** 1.270*** 0.257*** 0.402 0.720***
DRG 210 Hip & Femur Procedures Except Major Joint Age >17 w CC 0.365*** 13.455*** 0.570*** 11.361** 1.802*** 4.382***
Table 3-26. Regression Results Predicting Index Admission Length of Stay, Any PAC Use, and First Discharge Destination Using Independent Variable Set 3 (MS-DRGs + HCC), 2006
  OLS Regression
Predicting
Index Acute Admission LOS
Binomial Logit1
Predicting PAC/NoPAC
Multinomial Logit: Predicting Discharge Destination2
Variable Coefficient3 Odds Ratio3 Home Health
Odds Ratio3
IRF
Odds Ratio3
LTCH
Odds Ratio3
SNF
Odds Ratio3

1. Note that the reference group for the binomial logit is No PAC Use.
2. Note that the reference group for the multinomial logit is Hospital Outpatient Therapy.
3. Significance * p<0.05. ** p<0.01, *** p<0.0001.
4. The reference group for age is <65.
5. The reference group includes White, Asian, Hispanic, North American Native, Unknown, and Other.
6. The reference group for MS-DRG Severity Index is No CCs.
7. The reference group for each of the HCC variables is the absence of the HCC.
8. The reference group for the census division variables is New England.
9. The reference group for each of these variables is the absence of this type of organizational relationship.
10. The reference group is rural location.
11. The reference group is for-profit.

SOURCE: RTI analysis of 2006 Medicare claims 5% sample.

Intercept 2.904***          
Demographics Female 0.020 1.329*** 1.203*** 1.27*** 0.943 1.385***
Any Medicaid in 2005 0.355*** 1.301*** 0.657*** 0.535*** 1.044 1.266***
Age 65-744 -0.024 1.799*** 1.143** 1.221*** 0.715*** 1.46***
Age 75-84 0.126*** 2.808*** 1.383*** 1.526*** 0.917 3.087***
Ages 85 + 0.041 4.559*** 1.181*** 0.989 0.719** 4.248***
Black5 0.413*** 0.96** 1.156** 0.975 1.643*** 0.938
Severity6,7 MS-DRG Severity Index = CC 1.356*** 1.251*** 1.259*** 1.088* 1.235** 1.39***
MS-DRG Severity Index = MCC 3.426*** 1.698*** 1.2*** 1.267*** 1.926*** 1.835***
HCC80: Congestive Heart Failure 0.553*** 1.097*** 1.139*** 0.809*** 1.236** 1.071*
HCC92: Specified Heart Arrhythmias 0.735*** 0.995 1.213*** 1.111*** 1.402*** 1.159***
HCC108: Chronic Obstructive Pulmonary Disease 0.260*** 1.011 1.146*** 0.815*** 1.101 1.049
HCC19: Diabetes without Complication -0.392*** 1.003 1.113** 1.024** 0.74*** 1.04
HCC131: Renal Failure 0.752*** 1.13*** 0.869*** 0.791*** 1.399*** 0.943
HCC79: Cardio-Respiratory Failure and Shock 3.553*** 1.811*** 1.111* 1.58* 7.461*** 1.368***
HCC158: Hip Fracture/Dislocation 1.282*** 12.175*** 0.675*** 9.939*** 3.217*** 4.318***
HCC105: Vascular Disease 0.093** 0.852*** 1.127* 0.869* 1.043 0.981
HCC164: Major Complications of Medical Care and Trauma 2.700*** 1.974*** 1.681*** 2.326*** 2.874*** 1.528***
HCC96: Ischemic or Unspecified Stroke 0.730 3.465*** 0.538*** 5.363*** 1.983*** 0.937
HCC83: Angina Pectoris/Old Myocardial Infarction -0.802*** 0.686*** 1.051 0.874 0.358*** 0.761***
Supply IRF beds/1,000 beneficiaries/state -0.137** 1.002 0.739*** 1.885*** 1.45** 0.768***
SNF beds/1000 beneficiaries/state -0.002 1 0.974*** 0.987*** 0.977*** 0.998
LTCH beds/1000 beneficiaries/state -0.002 1.003** 1.338*** 1.057 1.878*** 1.162***
Census Division8 Middle Atlantic 0.720*** 0.793*** 1.078 1.073 1.075 0.841**
East North Central -0.240*** 0.673*** 0.643*** 0.665*** 1.08 0.636***
West North Central -0.233** 0.582*** 0.47*** 0.385*** 0.69 0.37***
South Atlantic -0.027 0.646*** 0.725*** 0.76** 0.697* 0.645***
East South Central -0.073 0.554*** 0.62*** 0.822* 0.997 0.561***
West South Central 0.102 0.489*** 0.842* 0.813* 2.362*** 0.304***
Mountain -0.444*** 0.588*** 0.616*** 0.859 1.279 0.663***
Pacific -0.190** 0.461*** 0.741** 0.862 1.541* 0.443***
Organizational Relationships of Discharging Acute Hospital9 Any Colocated Provider 0.007 1.006 - - - -
Any Subprovider 0.135*** 0.996 - - - -
Any Subprovider IRF - - 1.042 1.968*** 0.901* 0.829***
Any Subprovider SNF - - 0.953 0.769*** 0.784*** 1.185***
Any Subprovider HHA - - 0.991 0.916** 0.773*** 1.036
Any Colocated IRF - - 1.258* 2.349*** 0.829 0.928
Any Colocated SNF - - 1.073* 1.014 0.982 1.132**
Any Colocated HHA - - 0.885* 0.802** 0.947 0.862**
Any Colocated LTCH - - 0.863** 0.935 1.556*** 0.743***
Characteristics of Discharging Acute Hospital Number of Beds 0.001*** 1.000**        
Urban Location10 0.415*** 1.209***        
Not-for-profit11 -0.034 1.013        
Government run11 0.072* 0.933***        
Table 3-27. Regression Results Predicting Readmission During PAC Episode, 2006
  Binomial Logit Regressions
Predicting Readmission
OLS Regressions Predicting
Episode Payments
Variable Set 1
APR-DRG
Set 2
MS-DRG
Set 3
MS-DRGs
and HCCs
Set 1
APR-DRG
Set 2
MS-DRG
Set 3
MS-DRGs
and HCCs

1. Significance * p<0.05. ** p<0.01, *** p<0.0001.
2. The reference group for age is <65.
3. The reference group includes White, Asian, Hispanic, North American Native, Unknown, and Other.
4. The reference group for APR-DRG Severity Index is minor.
5. The reference group for MS-DRG Severity Index is No CCs.
6. The reference group for the census division variables is New England.
7. The reference group for each of these variables is the absence of this type of organizational relationship.
8. The reference group is rural location.
9. The reference group is for-profit.
10. The reference group for each of these variables is the absence of this DRG as the index acute admission DRG.
11. The reference group for each of the HCC variables is the absence of the HCC.
12. The reference group is outpatient therapy.

SOURCE: RTI analysis of 2006 Medicare claims 5% sample.

Demographics Female 0.889*** 0.878*** 0.924*** -688*** -950*** -411***
Any Medicaid in 2005 1.071*** 1.085*** 1.152*** 1,464*** 1,902*** 1,616***
Age 65-742 0.856*** 0.861*** 0.882*** 2,131*** 2,090*** 1,907***
Age 75-84 0.962 0.973 1.025 3,138*** 3,541*** 2,563***
Ages 85 + 0.967 0.992 1.12*** 2,825*** 3,689*** 1,838***
Black3 1.159*** 1.157*** 1.127*** 1,272*** 1,273*** 1,452***
Severity APR-DRG Severity Index = moderate4 1.412***     3,896***    
APR-DRG Severity Index = major 1.872***     11,389***    
APR-DRG Severity Index = extreme 1.916***     36,537***    
MS-DRG Severity index = CC5   1.212*** 1.293***   4,632*** 2,217***
MS-DRG Severity index = MCC   1.391*** 1.387***   11,995*** 6,313***
Supply IRF beds/1,000 beneficiaries/state 0.961 0.972 0.968 -1,555*** -1,649*** -1,862***
SNF beds/1,000 beneficiaries/state 0.998 0.999 1 -26* -26** -32***
LTCH beds/1,000 beneficiaries/state 1.040* 1.033* 1.021 1,044 979*** 1,088***
Census Division6 Middle Atlantic 1.160** 1.142* 1.112* 841** 806* 911**
East North Central 1.163** 1.162*** 1.108* -2,065*** -1,727*** -1,840***
West North Central 1.075 1.069 1.076 -3,619*** -3,510*** -3,494***
South Atlantic 1.014 1.022 0.988 -3,242*** -2,907*** -3,159***
East South Central 1.172** 1.181* 1.073 -3,388*** -3,226*** -3,388***
West South Central 1.307** 1.281*** 1.145** -1,453*** -1,147*** -1,229***
Mountain 0.927 0.934 0.961 -2,215*** -1,995*** -2,264***
Pacific 0.911 0.911* 0.9** -1,645*** -1,690*** -1,736***
Organizational Relationships of Discharging Acute Hospital7 Any Colocated Provider 0.985 0.982 1.006 340** 332** 348**
Any Subprovider 0.971 0.966* 0.973* 392*** 412*** 346**
Characteristics of Discharging Acute Hospital Number of Beds 1.000 1.000* 1.000* 3*** 4*** 3***
Urban Location8 1.066* 1.075*** 1.035* 3,757*** 4,221*** 4,105***
Not-for-profit9 0.930** 0.936* 0.94** -499*** -344* -497***
Government run9 0.961 0.961 0.988 208 262 75
IndexLOS 1.026*** 1.031*** 1.033***      
Acute DRG10 DRG 209 Major Joint & Limb Reattachment Procedures of Lower Extremity 0.421*** 0.436***   8,022*** 8,968***  
DRG 089 Simple Pneumonia & Pleurisy Age >17 w CC 0.944 0.955   -5,465*** -5,827***  
DRG 014 Specific Cerebrovascular Disorders Except TIA 1.015 0.992   7,726*** 6,972***  
DRG 127 Heart Failure & Shock 1.605*** 1.525***   -2,390*** -4,495***  
DRG 210 Hip & Femur Procedures Except Major Joint Age >17 w CC 0.931 0.902*   17,130*** 16,164***  
Comorbid Conditions11 HCC80: Congestive Heart Failure     1.287***     2,523***
HCC92: Specified Heart Arrhythmias     1.16***     2,577***
HCC108: Chronic Obstructive Pulmonary Disease     1.241***     -614***
HCC19: Diabetes without Complication     1.109***     -126
HCC131: Renal Failure     1.255***     2,784***
HCC79: Cardio-Respiratory Failure and Shock     0.999     14,900***
HCC158: Hip Fracture/Dislocation     1.003     16,707***
HCC105: Vascular Disease     1.187***     1,544***
HCC164: Major Complications of Medical Care and Trauma     0.98     12,604***
HCC96: Ischemic or Unspecified Stroke     1.143***     10,675***
HCC83: Angina Pectoris/Old Myocardial Infarction     1.998     -1,026***
First PAC Setting12 SNF 1.214 1.232*** 7.043***      
LTCH 1.196** 1.299*** 7.917***      
HHA 1.227 1.234*** 7.464***      
IRF 1.357 1.356*** 7.557***      
 

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