MODO DE REALIZACIÓN DE LA INVENCIÓN 10
1. OBTENCIÓN DE LOS COMPUESTOS DE LA INVENCIÓN 15
5.26. The steps in the measurement of health products for PPPs estimation are: (a) identification of homogeneous products, (b) measurement of quantities of products, (c) placing a value on products.
Identification of homogeneous products
5.27. In the PPP framework, the items for which costs are collected and reported should be comparable and representative within a basic heading (Eurostat-OECD, 2006). It is clear that such a list of items will not be exhaustive in that it covers all the activities within a type (as an example, inpatient hospital care). However, exhaustiveness is not necessarily required if the selected case types are considered representative for a broad set of activities.
5.28. Products are said to be comparable if they have identical or equivalent physical and economic characteristics – that is, if they have the same or similar technical parameters and price determining properties. In the context of PPPs, equivalence or similarity between products is defined as meeting the same needs with equal efficiency so that purchasers are indifferent between them and are not prepared to pay more for one than for the other. For non-market hospital products, this requirement is not easily fulfilled. For this reason, it may be necessary to rely on the identification of products that have the same or similar technical parameters, that is, they are homogeneous in terms of expected treatment profiles.
5.29. Representativity is a concept that relates to individual products within a basic heading. A product is called representative if it is generally found in the market and expenditure on the product accounts for (although not necessarily) a significant proportion of the total expenditure of all products covered by the basic heading. Normally, representativity of products cannot be accurately determined due to lack of information on expenditure proportions. In the context of non-market hospital products, the representativity requirement would be met if the case types represent common occurrences of treatments that are typically dealt with in hospitals and/or if there is evidence that the total costs of the selected products account for a sizable share of total hospital costs38.
5.30. The proposal foresees the categorization of case types into medical and surgical, the former being those cases for which no operating room procedure was reported to be performed. The following are the
37 In the remaining part of the document, we use the term DRGs to identify the case-mix measurement tool in general terms. We recognize that the taxonomy of the classification system varies across countries and that different systems are in place, such as Groupe Homegène de Malade in France or Australian Refined DRGs in Australia.
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criteria that could be used for identifying the hospitals case type list in the PPPs context. The case types should:
• Represent common procedures or diagnoses;
• Account for a significant percentage of hospital expenditures; • Identify cases likely to be admitted to a hospital;
• Represent procedures which are elective and are the principal procedure within one hospitalisation (for surgical case types);
• Represent well identified conditions without complications and/or comorbidities (for medical case types).
5.31. Annex C contains a proposed list of case types. The list is based on a proposed shortlist of inpatient case vignettes presented during the 1st Task Force39 meeting (Huber, 2007), on the proposal by
the Expert group on procedures under the Hospital Data Project (Smedby, 2007), on the list which is currently used at the OECD for Health Data collection (OECD, 2007), and on discussions held during the Task Force meetings. The criteria listed above were used for the selection of case types.
Measurement of quantities of these products
5.32. The comparison uses routinely collected information on inpatient activity and costs as a basis for data gathering and collating. The proposed approach limits the costs of collecting data by using secondary databases. Moreover, it may have the advantages of larger sample size and greater data validity. On the other hand, this approach requires an analysis of the classification logic used in each country to identify and measure case-mix, given the important differences among countries in the grouping logic.
5.33. To measure those case types, secondary data sets containing coded diagnosis and procedures information will be used. The first step of the process envisages the selection of International Classification of Disease, ninth revision, clinical modifications (ICD-9-CM) codes that identify each case type (column 2 of the tables contained in the Annex C) and the specification of rules for the selection of cases (column 3). 5.34. To handle the variations of coding schemata and ensure comparability of products definition, mapping tables have to be used from local codes to ICD-9-CM. For medical case types, the WHO International Shortlist for Hospital Morbidity Tabulation (ISHMT) (WHO, 2006) contains a mapping of ICD-10 diagnoses codes to ICD-9 diagnosis codes. For surgical cases, mapping tables for selected country
39 The Task Force for the Development of Health-Specific Purchasing Power Parities (TF) is a technical group
whose roles and responsibilities include: development of concepts and methodology; assessment of data availability and feasibility of data development; formulation of joint OECD/Eurostat guidelines for data collection for the purpose of health PPPs. All member countries of the OECD and non-OECD European Union members were invited to nominate participants to serve on the TF. Members of the TF are invited to participate actively in the programme of work by reviewing and commenting on papers and issues at TF meetings and preparation of papers on topics of interest. The leadership and administration of the TF is with the OECD. The TF reports in the first instance to the OECD Health Accounts Experts Group, and also to the OECD Health Committee and the OECD National Accounts Working Party. The reports of the TF are also made available to the Eurostat PPP Working Group. The TF sends its reports also to the Eurostat Partnership in Health Technical Group Care and the Eurostat Working Group on Public Health Statistics. The first meeting of the TF took place in Paris on 8 June 2007; the second one on 7-8 February 2008.
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procedure classification systems to ICD-9-CM are available through the Expert group on procedures under the Hospital Data Project.
5.35. The correspondence between each of the case types and a DRG is then reviewed through a qualitative evaluation of the taxonomy of the classification systems used by the individual country. The review of the contents of DRGs Definition manuals will allow us to state if:
• The case type corresponds to a DRG;
• The case type corresponds to more than one DRG. This is the case when the taxonomy uses factors as age or severity to split products corresponding to one case type;
• The case type is included in one DRG, and there are other case types included in the same DRG. This is the case when the clinical and resource consumption analysis does not justify the representation of a case type by a DRG (or family of DRGs).
5.36. For surgical case types, the review of the DRGs taxonomy will allow us also to evaluate if there are significant differences among countries as to the diagnoses for which the specific type of procedure is expected to be performed.
Placing a value on products
5.37. A universally accepted costing methodology does not currently exist in the health care sector. Approaches to resource consumption measurement vary widely, and are determined by the objective of the cost analysis and the availability of data (Mogyorosy, 2005; Wiley, 1993). On one end of the spectrum, there is the gross-costing or top down approach. On the other end, there is the bottom-up or micro-costing approach.
5.38. The gross-costing approach is essentially a product line (or case-mix) cost accounting model, with the core objective of costing individual patients grouped into similar classes. The basic information comes from the hospital’s general ledger. The reference Yale cost model40 has four basic steps (Fetter,
1976):
• Definition of the initial cost centres of the hospital, which include overhead cost centres or support services, ancillary services, and wards;
• Allocation of overhead costs to the remaining cost centres, ancillary services, and care units; • Allocation of ancillary services to the wards. This may be done according to actual use of
ancillary services or to indicated use;
• Allocation of the final cost centres to patient level/DRG groups, according to actual use of resources or some allocation statistics.
• Identification of clinical activities to describe treatment profiles;
• Identification of the discrete resource areas/intermediate cost centres which provide the identified activities;
40 The so called Yale cost model was developed by the Health System Management Group established in 1977 at Yale University. This entity, with Professor Fetter as director, has carried out all DRG-related work at Yale.
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5.39. In the direct identification and measurement of patient-specific service delivery process, frequently called bottom-up or micro-costing approach, five steps are taken in the process of defining patients’ resource use and cost profiles:
• Definition of appropriate workload measures for each resource area;
• Identification of individual patients’ treatment profiles, in terms of workload units of the relevant clinical activities performed;
• Place a value on workload units from each resource area in order to derive individual patients’ cost profiles.
5.40. Several countries measure resource utilisation retrospectively through a top-down or mixed approach. The hospital costing process usually begins with the general ledger. The purpose is that a control total for costing is established, and this should be the full cost of providing services to patients. The cost object could be either the DRG, or the case type, or the patient. The main difference relates to the allocation of costs from ancillary cost centres and direct cost centres to case types or patients. The most common methods of allocation are cost-to-charge ratios, weighted length of stay, actual costs, relative value units, and standard costs (Chandler, 1991). As an example, the English NHS requires a standard clinical and resource profile to be determined for the HRGs that cover at least 80 % of cost and activity at each point of delivery within a hospital. In Australia, there are service weights by AR-DRG available for each ancillary service. The results of these studies are benchmark or reference costs, and usually reflect the average observed cost by product. Costs are calculated on a full absorption basis to identify the full cost of services delivered.
5.41. The analysis of the correspondence between case types and DRGs is the basis for attaching a value to products. This will be done using the official unit costs values that are available through national cost studies. With respect to the three options described above, a unit cost will be computed as follows:
• The case type corresponds to a DRG. This is the easiest one, because unit costs values can be used as they are published;
• The case type corresponds to more than one DRG. In that case a weighted average of the unit costs by DRG can be used, the weights being the number of cases in the national sample. The case type is included in one DRG, and there are other diagnosis or procedures included in the same DRG.
It is proposed that countries will be asked to control for the within-DRG variability. This might be feasible provided that countries use allocation statistics at patient or diagnosis/procedure type or day of stay level.