Elective Services: Comparative Analysis of DHB Intervention Rates for selected Elective Services

Elective Services
Comparative Analysis of DHB Intervention Rates for selected Elective Services

In this section:

Introduction
Standardised Discharge Ratios: An explanation
Interpretation of Standardised Discharge Ratios
Using the SDR Information
Download the DHB Reports

In New Zealand there is an expectation that each District Health Board (DHB) will offer similar access to publicly funded elective services to the people in its area. Access is based on need, with people in greatest need being given treatment first.

For people with conditions that require immediate treatment (such as a heart attack) all DHBs make those conditions their highest priority. However, how quickly people get their treatment is affected by whether they live close to a big hospital or in a rural area with some distance to travel.

Similarly access to elective surgery for people with serious or potentially life- threatening conditions such as a major cancer is also reasonably consistent across the country. However, access to elective surgery for less serious conditions such as hernias is less consistent, with seemingly lower or higher levels in some DHBs than others. In some DHBs this reflects good primary health services, historical high levels of service provision to meet population needs, or may reflect difficulties with recruitment of Specialist staff.

Intervention rate analysis does not indicate what the right rate might be. It simply compares individual boards with the national average, taking board population demographics (age, sex, deprivation, and ethnicity) into account. It does not give information as to why the local rate may differ from the national average. DHBs have a good understanding of the local factors that are likely to be affecting the range and level of services required for their population.

For example, a DHB which has a Standardised Discharge Ratio (SDR) of 0.8 for dental procedures may be providing very good preventive and primary oral health services meaning that people in that district need less elective dental surgery than people in other parts of the country. In this instance an SDR below 1.0 is an indication of better than average overall dental services.

This analysis helps boards to see how they compare with the national average for elective services across a consistent set of procedures, as agreed by specialist clinicians at a Health Specialty level e.g. general surgery. The analysis focuses on the services given to the DHB’s resident population, allocates procedures to specific specialties and counts the procedure irrespective of which specialty it had been coded to.

This work comparing intervention rates has some significant limitations, for example, it includes only a portion of total elective delivery. However a careful analysis of standardised discharge ratios provides valuable information on how consistent access to the procedures included in this analysis is for New Zealanders, irrespective of where they live.

This analysis is useful for DHBs as they identify their priorities for increasing access to services and decide how best to spend their share of an extra $200 million for elective services over the next four years.

Standardised Discharge Ratios: An explanation
The reports for individual district health boards detail their intervention rates, compared to the national average, for a set of defined elective procedures within each specialty.

The specialties are: cardiology, cardio-thoracic, dental / oral facio-maxillary, ear, nose and throat, general surgery, gynaecology, neuro surgery, ophthalmology, orthopaedics, paediatric surgery, plastics, urology and vascular.

The defined procedures exclude those considered urgent, such as surgery for acute illness such as appendicitis, or surgery for life threatening conditions such as surgery for cancer, as these are procedures people across the country should receive consistently. They also exclude procedures for which some patients are admitted but in other hospitals are treated as an outpatient. The groups of defined procedures (referred to as "core" in the original reports) represent only a proportion of the total surgery performed. Table A gives the number of discharges for the defined procedures as a percentage of the total number of discharges from that specialty.

Using data supplied by DHBs to the National Minimum Data Set (NMDS) Standardised Discharge Ratios (SDRs) have been calculated for each specialty area. The standardised discharge ratio is the ratio between the number of operations completed and the number that would be expected to be completed if the DHB was providing the service at the national average rate. The expected number is worked out by taking the national rate and applying it to the board's population, adjusting for age, sex, social deprivation and ethnicity. This is the same method as used for the Standardised Discharge Ratios for 14 key marker cases that are published on the NZHIS website (www.nzhis.govt.nz).

Interpretation of Standardised Discharge Ratios
If all DHBs were providing services at the same level, then all SDRs would be at 1. A rate higher than 1 indicates that the population from that district is receiving more than the average rate for New Zealand, and a rate lower than 1 indicates that the people resident in that district are receiving less than the average rate. A standardised discharge ratio of 0.9 for a service means that people who live in that district receive 90 per cent of the national average for the group of specified procedures in that service.

Intervention rates will vary from year to year due to a range of factors - including variations in service delivery e.g. staff vacancies. These variations are naturally much greater when absolute numbers, either the size of the DHB population or the number of procedures performed are small. This random variation has been allowed for in the confidence limits analysis in the reports. If the confidence limits of an SDR cross 1.0 (e.g., 0.89 – 1.07), then it is not possible to say with confidence that the SDR is really different to the national average – it may simply be due to statistical variability. If however the confidence limit range of the SDR SDR is entirely above or below 1.0 (e.g., 0.77 – 0.95), then it can be concluded with 99% confidence that the SDR is genuinely higher or lower than the national average of 1.0, that is, not due simply to statistical variability. Similarly it is possible to compare one DHB with another only when the confidence limit ranges of the two SDRs do not overlap; otherwise differences in SDRs between DHBs may be due simply to statistical variability.

The reports also do not include patients who choose to pay for their own treatment within the private sector. Publicly-funded intervention rates in DHBs which have a high number of residents with private health insurance may be lower for this reason.

The SDRs in this analysis have been calculated for a group of defined procedures within each specialty. A low overall SDR does not necessarily mean that all procedures within the specialty are provided at a below average rate. In fact, some procedures within the group may even be provided at a higher than average rate even though the overall rate for the whole group is low.

Using the SDR Information
It is essential that DHBs explore the local factors which are influencing the SDRs in their district. It is expected that DHBs will use this information to help identify priorities for more service, and especially to guide decisions about allocating $200 million extra which the Government has made available to improve access to elective services.

One of the fundamental principles of the booking system is fairness. This data has been provided to help boards work out where they need to improve access to elective services, and particularly to ensure more consistent access across the country.

Reports for each DHB describe how the standardized discharge ratios were developed and findings for each DHB. These are provided in PDF format below:

Appendix one (PDF, 21 KB) describes how the working groups were set up and the methodology used.
Appendix two (PDF, 85 KB) lists the procedures that are included for each specialty as decided by the Clinicians representing that specialty in the working groups.
Appendix three (PDF, 68 KB) lists all the Standardised discharge ratios for each DHB and each specialty.
Table A (PDF, 7 KB)

Page last updated: 8 May 2007