school of population health the university of queensland measuring diabetes mortality: problems...
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SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Measuring diabetes mortality:
Problems & Prospects
Chalapati Rao
April 2011
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Outline Background
– Pathophysiology of diabetes mortality
– Conventions in coding and statistical presentation
– Current understanding of diabetes mortality
Multiple cause of death analyses– Diabetes – underlying cause vs ‘mentions’– Diabetes and IHD / Stroke– Diabetes and renal disease
Summary of issues
Prospects for consistent and comparable data
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Background / context
Diabetes is an increasing public health problem
Measures of incidence / prevalence are difficult to attain for various reasons
– Sampling issues / response rates / measurement error
Population level measures of mortality appear straightforward, from national death registration systems
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Medical certificate of cause of death
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Example 1
Cardiac arrest
Congestive heart failure
Myocardial infarction
Metastatic lung cancer
Mode of dying
Ia
Ib
II
Underlying cause of death: Myocardial infarction
Death certification
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Definition of underlying Cause of Death
When only one cause: select for tabulation
When several causes: “underlying” = the disease or injury, which initiated the train of morbid events leading directly to death, or the circumstance of the accident or violence which produced the fatal injury.
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Rules for ICD Coding Recommend primary tabulations based on underlying causes
(data submitted to WHO Mortality Database)
Rules for selection of underlying causes
– General Principle
– Selection rules 1 – 3
– Modification rules A – F
– Specific rules for individual causes (decision tables ~ several hundred
pages) CURRENTLY, AUTOMATED CODING SYSTEMS IN SEVERAL COUNTRIES, INCLUDING
AUSTRALIA AND USA
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Causes of diabetes deaths
DIABETES
Metabolic complications
Direct microvascular changes
Associated vascular changes
(Atherosclerosis)
Contributory cause
Ketoacidosis Hyperosmolar
coma Hypoglycaemia
Peripheral vascular / neural gangrene → sepsis
Diabetic renal disease
MI Stroke ? Diabetic
cardiomyopathy
Tuberculosis Cancer Pneumonia etc
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Rules for diabetes
Underlying causes coded to three broad categories– Insulin dependent DM – E10– Non-insulin dependent DM – E 11– Unspecified DM – E14
Each with 9 sub categories with a fourth character extension .0 – coma .1 - ketoacidosis .2 – renal complications .3 – ophthalmic complications .4 – neurological complications .5 – peripheral circulatory complications .6 – other specified complications .7 – multiple complications .8 – unspecified complications .9 – without complications
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Table 2: [C1] Distribution of numbers of fourth character diabetes UCOD coded deaths
Fourth character for UCOD E10 – E14
Australia USA
1999 2006 1999 2004
.0 – coma 34 29 688 464
.1 - ketoacidosis 38 65 1,894 1,810
.2 – renal complications 115 131 1,730 1,727
.3 – ophthalmic complications 7 5 49 31
.4 – neurological complications 11 12 392 394
.5 – peripheral circulatory complications 497 507 7,602 7,616
.6 – other specified complications 6 8 274 254
.7 – multiple complications 49 67 794 663
.8 – unspecified complications 3 - 177 55
.9 – without complications2,187
2,838
(78%)54,799
60,124 (82%)
Total deaths with diabetes as UCOD 2,947 3,662 68,399 73,138
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Multiple causes of death analysis
To explore magnitude of diabetes mortality as a co-morbidity with other conditions in general; and with cardiovascular / renal disease in particular
To explore the phenomenon of mortality coded to ‘diabetes without complications’
To assess potential influence of certification / coding practices on statistics
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Table 1. Trends in deaths from diabetes (underlying cause and total mentions on death certificate): numbers and percentage of total deaths for Australia (1999 and 2006) and USA (1999 and 2004).
Number of deaths (% of all deaths)
Australia USA
1999 2006 1999 2004
Diabetes UCOD 2,947 (2.3%)
3,662 (2 .7%) 68,399 (2.9%)
73,138(3.1%)
Diabetes listed on, certificate 9,588
(7.5%)12,811
(9.6%)209,679
(8.8%)225,455 (9.4%)
Preliminary data assessment
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Observations
Diabetes mentioned in Part II about twice as often as in part 1
Similar observations in data from Brazil, France, Sweden, and
several other European countries
This indicates its higher association with mortality than perceived
from underlying cause data
All this occurs in a backdrop of general under reporting of diabetes
on death certificates Diabetes listed as a single cause in only 1- 2% cases, so the deaths
coded to ‘DM without complications’ is a misrepresentation of reality
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Diabetes and Myocardial Infarction (MI) / Stroke
SPECIAL RULE
If MI / stroke listed as a consequence of diabetes in Part 1, then underlying cause is diabetes
If MI / stroke listed in Part 1, with Diabetes in Part II, then underlying cause is MI / stroke
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Example 1
Left ventricular failure
Myocardial infarction
Diabetes
Ia
Ib1c
II
Underlying cause of death: Diabetes
Death certification
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Example 2
Left ventricular failure
Myocardial infarction
Diabetes
Ia
Ib1c
II
Underlying cause of death: Myocardial infarction
Death certification
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Diabetes and Myocardial Infarction
Year Australia USA
UCOD Pt 2 UCOD % UCOD Pt 2 UCOD %
1999 1311 2312 36% 26168 52724 33%2000 1315 2345 36% 26578 52025 34%2001 1341 2400 36% 26870 51526 34%2002 1458 2452 37% 27474 50861 35%2003 1544 2291 40% 27544 50006 36%2004 1627 2235 42% 26916 47877 36%2006 1652 2129 44%
Deaths with MI in Part 1; and diabetes in Part 1 (UCOD) or Part 2
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Diabetes and Stroke
Year Australia USA
UCOD Pt 2 UCOD % UCOD Pt 2 UCOD %
1999479 762 39% 7817 12769 38%
2000463 759 38% 7743 12462 38%
2001510 802 39% 7814 12455 39%
2002535 828 39% 7658 12623 38%
2003612 795 43% 7455 12039 38%
2004644 788 45% 7317 11793 38%
2006659 862 43%
Deaths with stroke in Part 1; and diabetes in Part 1(UCOD) or Part 2
Diabetes is being increasingly listed in Part 1, thereby augmenting its magnitude in underlying cause mortality statistics
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Other evidence
Similar variations observed in other countries (Taiwan, Sweden)– South Africa is quite different with 98% of diabetes related deaths
having diabetes recorded in Part 1
Variation tested through clinical vignettes describing mortality from cardioavascular disease in diabetics
– Identified high degree of subjectivity in physcians, in the practice of listing Diabetes in part 1 vs Part 2, with concomitant MI / stroke
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Clinical / pathological perspective ‘Diabetes predisposes to cardiovascular diseases’
– Harrison’s Principles of Internal Medicine; 17th Edition
‘Diabetes mellitus, whether type 1 or type 2, is a very strong risk factor
for the development of coronary artery disease (CHD) and stroke’
– Hurst: The Heart – 12th Edition
‘Diabetes mellitus induces hypercholesterolemia and a markedly
increased predisposition to atherosclerosis’
– Robbins Pathologic Basis of Disease, 6th edition The American Heart Association has designated DM as a major risk
factor for cardiovascular disease (same category as smoking, hypertension, and hyperlipidemia)
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Inferences
Inconsistency in certification practices compounded by ambiguity in coding rules
As a result, Diabetes / CVD statistics based on underlying causes not readily comparable across countries, or over time
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Diabetes with renal complications
Clear relationship from pathological perspective
– Microvascular and basement membrane changes in glomerulus
producing distinctive Kimmelstein Wilson lesions PLUS
atherosclerotic changes in renal arterial vessels
Designated code in ICD rules
– BUT – some interesting fine print…..
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Table 2: [C1] Distribution of numbers of fourth character diabetes UCOD coded deaths
Fourth character for UCOD E10 – E14
Australia USA
1999 2006 1999 2004
.0 – coma 34 29 688 464
.1 - ketoacidosis 38 65 1,894 1,810
.2 – renal complications115
(3.9%) 131
(3.6%) 1,730
(2.5%) 1,727
(2.4%)
.3 – ophthalmic complications 7 5 49 31
.4 – neurological complications 11 12 392 394
.5 – peripheral circulatory complications 497 507 7,602 7,616
.6 – other specified complications 6 8 274 254
.7 – multiple complications 49 67 794 663
.8 – unspecified complications 3 - 177 55
.9 – without complications2,187
2,838
(78%)54,799
60,124 (82%)
Total deaths with diabetes as UCOD 2,947 3,662 68,399 73,138
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Coding rules for ‘DM with renal complications’
Coded as underlying cause IF any of the following
terms listed in part 1 of the death certificate
– Diabetic nephropathy
– Kimmelstein Wilson Disease
– Intracapillary Glomerulosclerosis
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Specific additional rule Coded to DM with renal complications IF
A) the death certificate lists DM in part 1; AND
B) with any of the following listed as a consequence, in Part 1– Unspecified disorder of the kidney or ureter (N28.9)– chronic nephritic syndrome (N03)– nephrotic syndrome (N04)– unspecified nephritic syndrome (N05) or – unspecified contracted kidney (N26)
RENAL FAILURE (N17-N19) listed as a consequence of Diabetes is not considered as Diabetes with renal complications
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Research hypothesis
Certifying physicians are more likely to write ‘RENAL FAILURE’ on death certificates, rather than the more complex terms listed in the rules
‘Diabetes with renal failure’ can be considered as ‘diabetic renal disease’
Question: What do the multiple causes of death data tell us about mortality from diabetic renal disease?
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Multiple cause of death data
1. Extract all deaths coded to DM as underlying cause
2. Create subset of deaths coded to ‘DM with renal complications’
3. THEN Screen all remaining DM UCOD deaths, for renal failure listed as a consequence of DM in Pt 1, to create additional deaths subsets
4. Additional deaths A: Deaths with UCOD -DM without complications; but with Renal failure listed in Pt 1
5. Additional deaths B: Deaths coded to other DM UCOD categories, but with renal failure listed in Pt 1
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Deaths from diabetic renal disease
Deaths
Australia USA
1999 2006 1999 2004
Diabetes with renal complications 115 131 1,730 1,727
Additional deaths ‘A’ 301* 577 11,543 13,739
Additional deaths ‘B’ 118# 169 2,166 2,241
Total diabetes UCOD 2,947 3,662 68,399 73,138
* out of 2187 deaths coded to DM without complications
# out of 645 deaths coded to diabetes with other categories of complications except renal or *
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Comparison of underlying vs mulitple cause rates
Age-standardised death
rates (per 100,000)*
USA Australia
1999 2004 % change 1999 2006 % change
Underlying cause rate
(UCR)0.68 0.62 -7.7 0.67 0.64 -5.3
Multiple cause rate 1
(MCR1)5.2 5.6 7.3 2.5 3.4 37.7
Rate ratio†
(95% CI)
7.7
(7.3 – 8.1)
8.9
(8.5 – 9.4)−
3.7
(3.0 – 4.6)
5.4
(4.5 – 6.5)−
Multiple cause rate 2
(MCR2)6.1 6.4 5.6 3.2 4.3 34.2
Rate ratio†
(95% CI)
9
(8.5 – 9.4)
10.3
(9.8 – 10.8)−
4.7
(3.9 – 5.8)
6.7
(5.6 – 8.0)−
*Standardised to Australian population in 2006. † To the UCR
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Time trends
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Summary
Conventional mortality statistics based on underlying causes mask true patterns of mortality from diabetes and its complications
Issues in certification, coding and statistical presentation result in this situation
These need to be addressed, to improve prospects of more realistic understanding of diabetes mortality, given the impending epidemic in the Asia Pacific region
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
Global availability of cause of death data : 2001
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© WHO 2003. All rights reserved
goodincompletepoor/non existant
Vital Registration
SCHOOL OF POPULATION HEALTHTHE UNIVERSITY OF QUEENSLAND
References / acknowledgements
1. Rao C, Adair T, Bain C, Doi SA. Mortality from diabetic renal disease: a hidden epidemic. Eur J Public Health. 2011 Jan 18. [Epub ahead of print]
2. Adair T, Rao C. Changes in certification of diabetes with cardiovascular diseases increased reported diabetes mortality in Australia and the United States. J Clin Epidemiol. 2010 Feb;63(2):199-204.