It must be noted that the cost estimates presented are not the total costs due to these complications for the Canadian diabetic population, but rather, the typical costs of key components in an episode of illness. Average per-patient total costs were estimated by applying unit costs to the likely course of treatment for each complication. The macrovascular complications considered in this analysis are acute myocardial infarction(AMI), angina pectoris, ischemic stroke, and transient ischemic attacks (TIA). Microvascular complications include various levels of nephropathy (i.e., microalbuminuria, gross proteinuria, ESRD), retinopathy (i.e., proliferative retinopathy, macular edema, blindness), symptomatic neuropathy, LEA, and foot ulcers. While LEA and foot ulcers have been considered as neuropathic microvascular complications in this analysis, there is also a macrovascular component to these complications. Hypoglycemia was also considered as an acute complication.
The methodology and format used for developing and presenting the cost estimates in this paper have been published in earlier papers addressing the same complications for the U.S., and major macrovascular costs in Canada [
12,
16]. The cost of each complication is reported separately for the "event" and for the subsequent "state". Event costs are those associated with resource use specific to the defining clinical event and include both acute care (initial management in an inpatient or outpatient setting) and event-related health care delivered subsequently in the first year. This care may include subacute inpatient care (i.e., rehabilitation units within an acute care hospital, rehabilitation hospitals, nursing home facilities), home health care, outpatient therapy, physician visits, day care and diagnostic and therapeutic procedures, depending on the complication addressed.
For many of the complications, the resulting management costs persist after the event because it has placed the patient in a new health state. For these complications it is important to consider the ongoing, or state, costs. The state costs presented in this paper refer to the annual management costs for years subsequent to the event year and reflect the typical utilization of health care services for the ongoing management of the given health state. Some of the complications (i.e., foot ulcers, hypoglycemia) however, may not have a permanent effect on a person's health state, as they are potentially reversible and thus episodic events that can occur more than once. Given that these conditions are limited in duration, only event costs are applicable and no state costs are reported.
All event and state costs reported in this paper are incremental to any recommended measures that take place as part of routine diabetes management, the costs of which are not included in this analysis.
Cost Sources
As no one data source was available from which to abstract resource use and cost-relevant data for this analysis, it was necessary to gather information from a variety of pertinent sources. Acute inpatient resource use and costs were derived primarily from the 1994–95 and 1995–96 Ontario Case Cost Project (OCCP) databases [
17,
18]. OCCP is a joint program of the Ontario Ministry of Health and the Ontario Hospital Association. It was initiated for the purpose of developing information based on case cost data for funding and hospital management purposes. Patients with the analysis-relevant complications were identified by a principal diagnosis code (Table
1) using International Classification of Diseases (ICD-9) codes [
19]. Where possible, only patients with a secondary diagnosis code of diabetes were included in the analysis. For example, diabetic patients admitted primarily for AMI were identified by a principal diagnosis code of AMI (ICD-9: 410.0–410.9) and a secondary diagnosis code documenting diabetes (ICD9:250.00–250.93). When the number of diabetic patients with a specific complication was insufficient to perform a reliable analysis, the population was expanded to include non-diabetic patients with that complication, as the focus of the analysis was to develop the cost of managing the complication and not diabetes. Additional cost-related information based on Case Mix Groupings (CMGs) for 1996 [
20] was also reviewed and used when necessary to supplement the ICD9-based data. Acute care hospital cost estimates include, all accommodation (e.g., routine and special care units), ancillary services (e.g., pharmacy, laboratory), emergency room, operating room, diagnostic and therapeutic procedures, and physician costs. As physician costs are not included in the OCCP data nor reported in the literature in sufficient detail, it was necessary to develop the corresponding resource use profiles. The OCCP data and the medical literature were used to develop these based on length of stay (LOS), physician service data, and the use of resource intensive services such as the emergency room, surgical procedures such as LEA, special care units, and consultations.
Table 1
ICD-9 codes used to identify inpatient groups. Diagnosis codes refer only to principal diagnosis or identifying procedure code
AMI | 410.00 – 410.91 |
Angina | 413.0 – 413.9, 411.1 |
Ischemic Stroke | 433.x1*, 434.xx¶, 436 |
TIA | 435.9 |
1st LEA | 84.10 – 84.17 |
2nd LEA | 84.10 – 84.17 |
Diabetic Foot Ulcer | 707.1 |
Hypoglycemia | 250.8 x§
|
Recognizing the need for continuation of health care services upon discharge, post-acute care resource use profiles were developed. To develop these profiles, data from OCCP on disposition at discharge were supplemented with information from the Alberta Ambulatory Care Costing project [
21], the Canadian Diabetes Association [
6], the Heart Disease and Stroke Foundation of Canada [
22,
23], Health Canada [
23‐
25], Canadian clinical practice guidelines [
26‐
28], other government and institutional reports [
29‐
33], provider survey data on day care and cardiac rehabilitation, and peer-reviewed literature [
34‐
38]. In order to maintain consistency with the OCCP data, Ontario provincial fee schedules and formulary [
39‐
41] were used as unit cost sources for physician-related care, laboratory tests, and medications. Additional references used for specific complications are noted within the appropriate sections of this paper.
Reimbursement for health care in Canada is largely provincial rather than federal; therefore in order to derive "national" costs, it was necessary to adjust provincial data. Published health and personal care data from Statistics Canada [
42] were used to derive a ratio between provincial and national healthcare costs by cost center for each province. Provincial unit costs were then adjusted using these ratios to derive the national equivalent.
There are several modalities of treatment for ESRD (e.g., hemodialysis, peritoneal dialysis, renal transplant). Annual costs of caring for patients on each of these were applied to the proportion of patients receiving that type of treatment to give a weighted average cost. While the distribution was taken from 1998 data, it was assumed that the ESRD population is in a steady state – that is, the patients leaving the ESRD populations and the patients entering the ESRD population during a given year have approximately the same modality distribution such that the overall distribution does not vary significantly from year to year. The distribution of treatment modalities for the 1998 Canadian ESRD population was obtained from the Canadian Institute for Health Information [
43‐
45]. There is a definite and discernable event cost for renal transplant versus the annual cost of managing someone who has had a renal transplant. Thus, to estimate the steady-state cost for ESRD, it was necessary to also estimate the costs of renal transplantation. This was achieved by applying the event year cost of a transplant to the proportion of patients who had received a renal transplant during 1998 (transplant year) and combining that with the annual management cost applied to the proportion receiving a transplant during a previous year. The average annual costs of caring for a patient during the transplant year and in a subsequent year were obtained from the literature [
46]. The average annual cost of treatment for hemodialysis and that for peritoneal dialysis were taken from a 1998 report published by the
Agence d'évaluation des technologies et des modes d'intervention en santé (AÉTMIS) of Québec [
47]. These costs were updated to year 2000 and "nationalized" according to the methodology described above.
The majority of the unit cost and resource use data used in this analysis were derived from Canadian sources. For rare exceptions pertaining to post-acute care, it was necessary to rely on resource use data from other sources. For example, no Canadian data were available for post-acute care following discharge from coronary artery bypass graft (CABG) or percutaneous transluminal coronary angioplasty (PTCA) readmissions in diabetic patients who had a previous AMI. Thus, it was necessary to employ diagnosis-specific disposition distributions for a similar population from five 1996/97 US all payer state databases to derive initial post-acute care patterns. The proportions were then adjusted to reflect the difference between Canadian and US case fatality rates for diabetic patients with AMI. Also, although initial discharge disposition data from Canada were used in the analysis, Canadian data detailing transitions to other levels of care over time for those with disabling strokes were not available; therefore we used our stroke economic model [
48] to derive the state costs for stroke. The long-term transition data used in this model come from Sweden [
49].
Only direct medical costs, those directly related to delivery of the health care service, are included in the estimates reported here. All event and state cost estimates are reported in 2000 Canadian dollars. Where 2000 values were not available, older estimates were inflated using the Health Care Inflation Index, a component of the Consumer Price Index, supplied by Statistics Canada [
42].