Biomedical comorbidity
Introduction
To assist users who are interested in the presence of more than one condition, three comorbidity data items have been created for the biomedical collection in the IHMHS. These data items cover cardiovascular disease (CVD), chronic kidney disease (CKD), and diabetes. They have been calculated from both self-reported conditions and conditions based on biomedical data.
Definition
For the purposes of deriving the comorbidity data items, the following input definitions were used:
- CVD was calculated using only self-reported data. To have CVD, respondents needed to self-report one or more cardiovascular conditions from the ICD10-Mini classification. For more information, see the National Health Measures Survey methodology, 2022–24.
- CKD was calculated using only biomedical data. To have CKD, respondents needed to be classified as having Stage 1 – Stage 5 CKD. CKD stages are based on eGFR and albuminuria data items. For more information, refer to Chronic Kidney Disease (CKD) biomarkers.
- Diabetes prevalence was calculated using both biomedical and self-reported data. Three data items are available to assess diabetes status based on FPG or HbA1c results, or both, combined with self-reported diabetes and medication use. For more information on the diabetes prevalence items, refer to Diabetes biomarkers.
| Input items | Derived comorbidity data item | ||
|---|---|---|---|
| Comorbidity (CVD, CKD, diabetes prevalence using HbA1c) | Comorbidity (CVD, CKD, diabetes prevalence using FPG) | Comorbidity (CVD, CKD, diabetes prevalence using FPG and HbA1c) | |
| CVD (self-report) | Yes | Yes | Yes |
| CKD (biomedical) | Yes | Yes | Yes |
| Diabetes - HbA1c (self-report and biomedical) | Yes | No | No |
| Diabetes - FPG (self-report and biomedical) | No | Yes | No |
| Diabetes – FPG and HbA1c (self-report and biomedical) | No | No | Yes |
Methodology
The populations for comorbidity data items depends on which biomedical tests were used and are presented in the table below.
| Biomedical comorbidity item | Population |
|---|---|
| Comorbidity using HbA1c | Persons aged 18 years and over who provided a blood and urine sample |
| Comorbidity using FPG | Persons aged 18 years and over who provided a blood and urine sample, and fasted 8 hours or more prior to their blood test |
| Comorbidity using FPG and HbA1c | Persons aged 18 years and over who provided a blood and urine sample, and fasted 8 hours or more prior to their blood test |
Using the input conditions, the following output categories were produced for each comorbidity item:
0. Not applicable (not in the comorbidity item population)
1. Diabetes only
2. CKD only
3. CVD (self-report) only
4. Diabetes and CKD only
5. Diabetes and CVD (self-report) only
6. CKD and CVD (self-report) only
7. Diabetes and CKD and CVD (self-report)
8. Does not have diabetes or CKD or CVD (self-report).
Interpretation
In the comorbidity items, each respondent is allocated to only one category. Where people had a ‘not known’ or ‘unable to determine’ status for a biomedical input item, they were treated as not having that condition.
In order to create flexibility with the use of this item, categories 1 to 3 (which contain persons with only one condition) and category 8 (which contain persons with none of the conditions) were produced.
To produce frequencies based on different combinations of these conditions, users can collapse categories as required. For example, to determine those people with either Diabetes or CKD, combine categories 1, 2, 4, 5, 6 and 7. To determine those people who don't have CVD, combine categories 1, 2, 4 and 8.