Northwest Renal Network

Mortality Report 1999-2001

 

 

 

December 25, 2002

 

 

Northwest Renal Network

4702 – 42nd Ave SW

Seattle WA 98116

(206) 923-0714

fax (206) 923-0716

 

 

prepared by Jim Buss, MA, CDP

jbuss@juno.com

 

 

 

 

 

 

 

 

 

 

This report has been prepared under contract #500-00-NW16 with the

Centers for Medicare and Medicaid Services

 

 

            Northwest Renal Network Mortality Report, 1999-2001

December  25, 2002

 

 

After a one-year hiatus, this is the sixth in our series of annual Network Mortality Reports.

 

A Standardized Mortality Ratio (“SMR”) compares mortality in a small population of patients, to mortality in a larger or reference population.  An SMR of 1.00 means that mortality in the smaller population is the same as mortality in the reference population.

 

An SMR of 1.20 means that mortality in the smaller population is 20% higher than mortality in the reference population, and an SMR of 0.80 means that the smaller population has experienced 20% less mortality than that of the reference population.

 

In this report we compare mortality among chronic kidney dialysis patients in the Pacific Northwest (Washington, Oregon, Idaho, Montana, Alaska) during 1999-2001, to mortality among chronic kidney dialysis patients in the United States as a whole during the year 2000.  That is, our “smaller population” is patients in the Northwest, and our “reference population” is patients in the US as a whole.  For this comparison, patients are stratified by age, race, primary renal diagnosis, modality of treatment, and gender.

 

Our reference population rates are from the United States Renal Data System (“USRDS”).  These rates can be found in tables H-4 and H-5 in section H on the website, http://www.usrds.org/reference.htm.

 

The method of comparison we use is a simple one.  We look up an “expected mortality” for each patient in the national tables, based on their age, race, primary renal diagnosis, modality, and gender.  We also compute 95% confidence intervals on each patient’s “expected mortality,” based on how much variation there is nationally among patients of this particular age-race-diagnosis-modality-gender group.  An expected mortality is a fraction between zero and one which indicates a patient’s likelihood of dying within one year.

 

Then for any group of patients, we simply add up each patient’s expected mortality, and add up each patient’s “actual mortality.”  “Actual mortality” is either zero if the patient is still alive, or one if not. 

 

The SMR for the group is the total actual mortality divided by the total expected mortality. 

 

We also compute an upper 95% confidence interval on the SMR by dividing total actual mortality by the sum of the lower confidence interval for each patient’s expected mortality, and compute a lower 95% confidence interval on the SMR by dividing total actual mortality by the sum of the upper confidence interval for each patient’s expected mortality.  This method is explained in detail at

http://www.nwrenalnetwork.org/mortality/runsmrci.htm.

 

This method works very well for small groups of patients, and it’s a conservative method – that is, it’s unlikely to label a group as having high mortality when in fact it doesn’t.

 

A group is considered to have statistically significantly high mortality (at p < 0.05) if the lower confidence interval of its SMR is greater than 1.00.

 

 

Note: Since the method is conservative, however, it could label a group as not having low mortality when in fact it does.

 

A group is considered to have statistically significantly low mortality if the upper confidence interval of the SMR is less than 1.00. 

 

If your group has an upper confidence interval greater than 1.00 and there are more than about 20 patients in the group, you can calculate an alternate upper confidence interval in the following way.  Divide the total actual deaths by the square of the total expected deaths.  Take the square root of the result, and multiply by 1.96.  Add this to your SMR to obtain your adjusted upper confidence interval.  The more patients there are in your group, the greater the difference between this confidence interval and the one calculated by the method used in our program.  If this new upper confidence interval is less than 1.00, your mortality is statistically significantly low, at p < 0.05.  This alternate calculation is the same one that was used in our previous Mortality Reports.
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


We eliminate patients during their first ninety days on dialysis ever, but we don’t exclude patients because of a failed prior transplant, a previous recovery episode, or a previous withdrawal episode.  Except for excluding that first ninety days, we count patients whenever they’re on dialysis in this Network.  Patients are counted at a facility whenever they are dialyzing there, and deaths are attributed to the facility at which the patient last dialyzed, even if the patient withdrew from dialysis prior to death.  The SMR reports from the University of Michigan Kidney Epidemiological Center (and the Colorado Foundation for Health Care) use different methods, different assumptions, and a different dataset.

 

 

Summary of Results

 

In our 1997-1999 Mortality Report, we reported statistically significantly high mortality for Native American patients, high mortality for a number of Network facilities, and trends toward higher relative mortality (that is, SMRs) among female patients, patients with a primary renal diagnosis of diabetes, and in-center hemodialysis patients. 

 

We’re happy to report that in the 1999-2001 period none of these subgroups has significantly high mortality, and no subgroup demonstrates a trend toward increasing mortality.

 

We’ve printed out two different sets of tables.  The first set gives SMRs by year over the three-year period, 1999-2001.  The second set shows the last six quarters, through October 2002.  For the Network as a whole, these tables are reproduced on pages 7-8.

 

 

Native American Patients

 

For Northwest Native American patients, the actual mortality rate has statistically significantly decreased, from 24% in 1997 to 19% in 1999 to 16% in 2001 (p < 0.05), and the SMR is no longer higher than 1.00.

 

During this time span the average age of Network Native American patients rose from 56.4 to 56.8.  The SMR for these patients in 2001 was 0.90, not yet

 

 

Figure 1.  Comparing Actual Mortality Rates for Native American Patients and All Patients, US versus Network, 1997-2001

 

statistically significantly lower than US Native American patients, but if the current trend continues, it will take us there soon.  In prior reports, mortality for Network Native American patients has been statistically significantly higher than mortality for all US Native American patients.  Figure 1 shows the decline in actual mortality rates.  SMRs for Native American patients are tabled on page 9.

 

 

Individual Facilities with High Overall SMRs

 

We asked thirteen facilities which had high SMRs in our earlier 1997-1999 Mortality Report to prepare QI plans to investigate possible root causes for these high SMRs, and to see if they could reduce their mortality – and they did.

 

At these thirteen facilities taken together, the actual mortality rate fell from 34% in 1999 to 24% in 2001, and the SMR from 1.61 to 1.02.  This is a statistically significant reduction that extended more than a hundred lives. 

 

Only three of the thirteen facilities remain statistically significantly high in the year 2001, and all three have substantially lower SMRs.

 

 

Figure 2.  SMRs by Facility for All Patients

 

 

In the 1999-2001 period, fifteen currently operating facilities demonstrate statistically significantly high mortality, but many of these are trending down.  Only seven statistically significantly high facilities show uptrends or consistently high SMRs during 1999-2002, and the Network will work with these facilities.  We’re excluding facilities with less then ten patient-years during 1999-2001.  Twenty-six facilities had statistically significantly low mortality.  Individual facilities are plotted in Figure 2.

 

 

Patients with a Primary Renal Diagnosis of Diabetes

 

While patients with a primary renal diagnosis of diabetes have a 1999-2001 SMR of 1.0 in the Network as a whole, there remain seventeen currently operating facilities with statistically significantly high 3-year SMRs for these patients.

 

 

Figure 3.  SMRs by Facility for All Patients with a Primary Renal Diagnosis of Diabetes

 

This compares to twenty-six facilities with statistically significantly low SMRs for patients with a primary renal diagnosis of diabetes.  These are plotted on Figure 3.  Again we’ve excluded facilities with less than ten patient-years.  We will work with selected facilities that have high SMRs for diabetic patients, at the very least to make sure everyone is familiar with the new literature on treating diabetic dialysis patients (http://www.renalweb.com/topics/out_diabetes/diabetes.htm).

 

 

 

 

 

 

Patients with a Primary Renal Diagnosis of Hypertension

 

Network patients with a primary renal diagnosis of hypertension also have an overall 1999-2001 SMR of 1.0, but there are twenty currently operating facilities with statistically significantly high 3-year SMRs for these patients.

 

 

Figure 4.  SMRs by Facility for All Patients with a Primary Renal Diagnosis of Hypertension

 

Twenty-one facilities have statistically significantly low 3-year SMRs for these patients.  Figure 4 plots these facilities.  Again, we’ve excluded facilities with less than ten patient-years. 

 

We will work with selected facilities that have high SMRs for hypertension patients, at the very least to make sure everyone is familiar with the new literature on treating hypertensive dialysis patients (http://www.renalweb.com/topics/out_bp/bp.htm).

 

 

 

 

 

 

 

 

Northwest Renal Network Mortality Report

All Patients                                                                           1/1/1999 to 1/1/2002

               Standard mortality rate data source: USRDS national rates for 2000.

               Calculated figures exclude the First 90 Days of Dialysis ever

                    Date Range            Pat           Pat      Deaths   Actual      Exptd      SM       Lower   Upper

                                                Count       Years                   Rate      Deaths    Ratio      Conf     Conf

  All

                1/1/1999 to  1/1/2000        8055        5876.6       1405       0.239       1395.0        1.01        0.86       1.21

                1/1/2000 to  1/1/2001        8562        6203.2       1507       0.243       1442.8        1.04        0.90       1.25

                1/1/2001 to  1/1/2002        9016        6626.0       1482       0.224       1516.6        0.98        0.84       1.17

                1/1/1999 to  1/1/2002       13090      18705.8       4394       0.235       4354.4        1.01        0.87       1.21

  Black

                1/1/1999 to  1/1/2000          743         585.9         104       0.177        100.7        1.03        0.89       1.23

                1/1/2000 to  1/1/2001          783         603.8         100       0.166          99.9        1.00        0.86       1.20

                1/1/2001 to  1/1/2002          813         646.5          87       0.135        103.3        0.84        0.72       1.01

                1/1/1999 to  1/1/2002        1118        1836.2         291       0.158        303.9        0.96        0.82       1.14

  Female

                1/1/1999 to  1/1/2000        3641        2673.0         663       0.248        645.2        1.03        0.88       1.23

                1/1/2000 to  1/1/2001        3852        2799.6         682       0.244        656.2        1.04        0.89       1.25

                1/1/2001 to  1/1/2002        4063        2981.8         671       0.225        684.0        0.98        0.84       1.18

                1/1/1999 to  1/1/2002        5876        8454.4       2016       0.238       1985.5        1.02        0.87       1.22

  In-Center Hemodialysis Patients

                1/1/1999 to  1/1/2000        6881        4821.3       1196       0.248       1164.3        1.03        0.88       1.23

                1/1/2000 to  1/1/2001        7419        5213.9       1323       0.254       1232.9        1.07        0.92       1.28

                1/1/2001 to  1/1/2002        7894        5617.6       1317       0.234       1307.3        1.01        0.87       1.21

                1/1/1999 to  1/1/2002       11582      15652.8       3836       0.245       3704.4        1.04        0.89       1.24

  Home Peritoneal Dialysis Patients

                1/1/1999 to  1/1/2000        1357         842.6         167       0.198        185.5        0.90        0.76       1.10

                1/1/2000 to  1/1/2001        1311         809.1         145       0.179        172.2        0.84        0.71       1.03

                1/1/2001 to  1/1/2002        1337         849.6         130       0.153        177.2        0.73        0.62       0.90

                1/1/1999 to  1/1/2002        2316        2501.3         442       0.177        534.9        0.83        0.70       1.01

  Diabetes

                1/1/1999 to  1/1/2000        3193        2278.3         662       0.291        629.5        1.05        0.91       1.25

                1/1/2000 to  1/1/2001        3457        2440.7         700       0.287        655.8        1.07        0.92       1.27

                1/1/2001 to  1/1/2002        3683        2681.1         674       0.251        711.6        0.95        0.82       1.13

                1/1/1999 to  1/1/2002        5409        7400.1       2036       0.275       1996.9        1.02        0.88       1.22

  Hypertension

                1/1/1999 to  1/1/2000        1402        1004.0         279       0.278        293.6        0.95        0.81       1.15

                1/1/2000 to  1/1/2001        1494        1074.9         306       0.285        308.1        0.99        0.85       1.20

                1/1/2001 to  1/1/2002        1615        1147.6         335       0.292        318.8        1.05        0.90       1.27

                1/1/1999 to  1/1/2002        2344        3226.5         920       0.285        920.4        1.00        0.85       1.20

                                                                                                                                                          


Northwest Renal Network Mortality Report

All Patients                                                                        4/1/2001 to 10/1/2002

               Standard mortality rate data source: USRDS national rates for 2000.

               Calculated figures exclude the First 90 Days of Dialysis ever

                    Date Range            Pat           Pat      Deaths   Actual      Exptd      SM       Lower   Upper

                                                Count       Years                   Rate      Deaths    Ratio      Conf     Conf

  All

                4/1/2001 to  7/1/2001        7157        1632.0         335       0.205        402.8        0.83        0.71       1.00

                7/1/2001 to  10/1/200        7357        1696.1         379       0.223        418.8        0.91        0.78       1.09

                10/1/200 to  1/1/2002        7425        1708.3         391       0.229        418.3        0.93        0.80       1.12

                1/1/2002 to  4/1/2002        7457        1685.0         419       0.249        407.6        1.03        0.88       1.23

                4/1/2002 to  7/1/2002        7631        1742.0         367       0.211        419.9        0.87        0.75       1.05

                7/1/2002 to  10/1/200        7834        1805.4         396       0.219        435.9        0.91        0.78       1.09

                4/1/2001 to  10/1/200       10567      10268.8       2287       0.223       2503.3        0.91        0.78       1.10

  Diabetes

                4/1/2001 to  7/1/2001        2916         661.3         155       0.234        187.0        0.83        0.71       0.99

                7/1/2001 to  10/1/200        2994         687.8         178       0.259        194.6        0.91        0.79       1.09

                10/1/200 to  1/1/2002        3017         693.4         178       0.257        195.5        0.91        0.78       1.08

                1/1/2002 to  4/1/2002        3058         684.2         195       0.285        190.9        1.02        0.88       1.22

                4/1/2002 to  7/1/2002        3130         712.5         168       0.236        198.2        0.85        0.73       1.01

                7/1/2002 to  10/1/200        3175         737.8         166       0.225        204.8        0.81        0.70       0.97

                4/1/2001 to  10/1/200        4333        4177.0       1040       0.249       1171.0        0.89        0.76       1.06

  Hypertension

                4/1/2001 to  7/1/2001        1251         282.4          75       0.266          85.5        0.88        0.75       1.06

                7/1/2001 to  10/1/200        1293         295.0          82       0.278          89.2        0.92        0.79       1.11

                10/1/200 to  1/1/2002        1308         295.7          91       0.308          88.7        1.03        0.88       1.24

                1/1/2002 to  4/1/2002        1292         289.5          90       0.311          86.0        1.05        0.89       1.26

                4/1/2002 to  7/1/2002        1327         299.8          76       0.254          89.0        0.85        0.73       1.03

                7/1/2002 to  10/1/200        1379         312.6          98       0.314          93.2        1.05        0.90       1.27

                4/1/2001 to  10/1/200        1912        1774.9         512       0.288        531.6        0.96        0.82       1.16

                                                                                                                                                          


Northwest Renal Network Mortality Report

Native Americans                                                            1/1/1999 to 1/1/2002

               Standard mortality rate data source: USRDS national rates for 2000.

               Calculated figures exclude the First 90 Days of Dialysis ever

                    Date Range            Pat           Pat      Deaths   Actual      Exptd      SM       Lower   Upper

                                                Count       Years                   Rate      Deaths    Ratio      Conf     Conf

  All

                1/1/1999 to  1/1/2000          344         252.8          49       0.194          47.5        1.03        0.81       1.43

                1/1/2000 to  1/1/2001          359         280.8          50       0.178          50.4        0.99        0.78       1.36

                1/1/2001 to  1/1/2002          390         305.6          48       0.157          53.2        0.90        0.71       1.25

                1/1/1999 to  1/1/2002          529         839.2         147       0.175        151.2        0.97        0.76       1.34

  Native American

                1/1/1999 to  1/1/2000          344         252.8          49       0.194          47.5        1.03        0.81       1.43

                1/1/2000 to  1/1/2001          359         280.8          50       0.178          50.4        0.99        0.78       1.36

                1/1/2001 to  1/1/2002          390         305.6          48       0.157          53.2        0.90        0.71       1.25

                1/1/1999 to  1/1/2002          529         839.2         147       0.175        151.2        0.97        0.76       1.34

  Female

                1/1/1999 to  1/1/2000          185         136.1          24       0.176          26.5        0.91        0.72       1.22

                1/1/2000 to  1/1/2001          203         161.9          27       0.167          29.5        0.91        0.73       1.22

                1/1/2001 to  1/1/2002          215         174.5          21       0.120          29.6        0.71        0.56       0.96

                1/1/1999 to  1/1/2002          282         472.5          72       0.152          85.6        0.84        0.67       1.13

  In-Center Hemodialysis Patients

                1/1/1999 to  1/1/2000          311         222.4          44       0.198          41.3        1.07        0.86       1.41

                1/1/2000 to  1/1/2001          326         247.6          44       0.178          44.7        0.98        0.79       1.30

                1/1/2001 to  1/1/2002          357         270.9          47       0.174          47.3        0.99        0.80       1.31

                1/1/1999 to  1/1/2002          483         740.9         135       0.182        133.3        1.01        0.82       1.34

  Home Peritoneal Dialysis Patients

                1/1/1999 to  1/1/2000           41           24.8            4       0.162           5.2        0.76        0.49       1.78

                1/1/2000 to  1/1/2001           43           26.8            5       0.187           4.6        1.10        0.70       2.59

                1/1/2001 to  1/1/2002           45           29.4            1       0.034           5.1        0.20        0.12       0.51

                1/1/1999 to  1/1/2002           77           81.0          10       0.123          14.9        0.67        0.42       1.63

  Diabetes

                1/1/1999 to  1/1/2000          207         146.5          31       0.212          31.6        0.98        0.79       1.28

                1/1/2000 to  1/1/2001          219         172.3          33       0.192          35.5        0.93        0.75       1.21

                1/1/2001 to  1/1/2002          239         182.1          33       0.181          36.0        0.92        0.75       1.19

                1/1/1999 to  1/1/2002          325         500.9          97       0.194        103.1        0.94        0.76       1.23

  Hypertension

                1/1/1999 to  1/1/2000           22           18.2            3       0.165           3.8        0.79        0.59       1.19

                1/1/2000 to  1/1/2001           23           17.8            4       0.224           3.1        1.27        0.94       1.96

                1/1/2001 to  1/1/2002           26           19.6            2       0.102           3.4        0.58        0.43       0.88

                1/1/1999 to  1/1/2002           34           55.7            9       0.162          10.4        0.87        0.65       1.31

                                                                                                                                                          


Reading Your Facility’s Tables

 

SMR tables for the Network as a whole are on the previous three pages.  The tables for your facility are just like pages 7-8, so we’ll use these Network tables to explain how to read all of the tables.

 

There are seven sections on the first one-page table: All patients, Black patients, Female patients, In-Center Hemodialysis Patients, Home Peritoneal Patients, patients with primary renal diagnosis of Diabetes, and patients with primary renal diagnosis of Hypertension.  If your facility is small or new, you may not have all sections – if you treated no black patients, for instance, then your table won’t have a separate section for black patients.  Each section (except “All “ of course) represents a subpopulation of patients.

 

In each section there are four rows – one row for each year, and a fourth row, in bold, for all three years together.  If your facility is new or has closed, all years may not appear.

 

On the second one-page table there are three sections: All patients, patients with primary renal diagnosis of Diabetes, and patients with primary renal diagnosis of Hypertension.  Again, your facility may not have all sections.  On this table there are seven rows per section – one row for each of the last six quarters, and a seventh row in bold for all six quarters together.

 

The most important column is the one in bold labeled “SM Ratio” – that’s your SMR, for each year and subgroup.

 

The last two columns are the lower and upper 95% confidence intervals around this SMR, using the conservative method we describe at

http://www.nwrenalnetwork.org/mortality/runsmrci.htm.  These columns are labeled “Lower Conf “ and “Upper Conf.”  If you have more than twenty patients and you want narrower confidence intervals, you can use the formula in the box on page 2.

 

The SMR is obtained by dividing actual mortality by expected mortality.  These two numbers are included in the tables under the column headings “Deaths” (actual deaths) and “Exptd Deaths” (expected deaths).  If you want to know the SMR for any combination of facilities or other subgroups, you can just add up the actual mortalities and the expected mortalities of each subgroup, and then divide.

 

For convenience, there’s an extra column labeled “Actual Rate” which gives the crude mortality rate for the period – number of deaths divided by number of patient-years.  If you want to compare the numbers on this report with the numbers in previous reports, this is a better number to use than the SMR, because the SMRs in different reports are calculated using different, then-most-recent, national reference rates.  So, for instance, your 1999 SMR in your 1997-1999 Mortality Report will be different from your 1999 SMR in your 1999-2001 Mortality Report, because they’re calculated from different reference points.  But your Actual Rate should be the same (or very close) on both reports.

 

The “Pat Count “ column gives the number of individual patients in your SMR.  If a patient dialyzed at your facility every other month, and at some other facility in the months in between, they’d be at your facility six times a year – but they’d always be counted as only one patient in the Pat Count column.

 

The “Pat Years” column, however, will count the total fraction of a year that any patient is being treated at your facility.  Our friend who spends every other month at your facility would be counted as 0.5 Pat Years, the same as a patient who dialyzed at your facility from the beginning of March through the end of August.  A patient who was at your facility – or in the subpopulation – all year would be

counted as 1.0 Pat Years.

 

We’ve omitted the SMR calculation whenever the expected mortality on any row is less than one.  We’ve done this to avoid showing misleadingly large SMRs; if your expected mortality was 0.1 and your actual mortality was 3, you’d have an SMR of 30, which would look very serious, but it’s much more likely that you just didn’t have enough patients in that subcategory to get a realistic calculation.

 

The USRDS provides national rates for In-Center Hemodialysis and for CAPD/CCPD.  For our “Home Peritoneal Dialysis Patients” section, we count only CAPD and home CCPD patients.  We have not counted patients on other peritoneal modalities because there are so few of them.