Original Papers

Sarah Wordsworth1 · Anne Ludbrook2 · Fergus Caskey3 · Alison Macleod4

1 Health Economics Research Centre, University of Oxford, Oxford, UK2 Health Economics Research Unit, University of Aberdeen, UK 3 Richard Bright Renal Unit, Bristol, UK 4 Department of Medicine and Therapeutics, University of Aberdeen, UK

Collecting unit cost data in multicentre studiesCreating comparable methods

Eur J Health Econom 2005 · 50:38–44DDOI 10.1007/s10198-004-0259-9Published online: 17. November 2004© Springer Medizin Verlag 2004

In recent years there has been increas-ing interest in international comparisons of health care systems and health care ser-vices, despite these being notoriously dif-ficult to perform and interpret []. This trend reflects two main factors. Firstly, the information provided by such com-parisons can inform policy development within each country, and, secondly, trials of new treatments are increasingly carried out on a multi-country basis. Clinical stud-ies including trials have been conducted on this basis for some time, although the collection of multi-country economic da-ta is a more recent development [2].

The challenges in conducting costing studies across centres, whether within one country or across countries, are well recog-nised [3, 4, 5, 6]. An issue of growing con-cern is how to collect health care unit costs in different countries on a comparable ba-sis, and whether a consistent approach can be found to increase the comparabil-ity of subsequent results. Whilst consisten-cy and accuracy of data collection are cru-cial to any approach adopted, transparen-cy is also important so that it is clear what items contribute towards total cost. There-fore transparent methods may allow for adjustments to be made even if data have been collected in different ways, leading to more comparable results. Some studies have addressed the issue of comparability in the context of pooling data from differ-ent countries and centres in the context

of clinical trials [7]. However; evidence suggests that in general there is too little transparency in the costing literature to al-low results to be applied in different poli-cy contexts from those in which the stud-ies were performed. For example, a review of economic evaluation studies of women with breast cancer undergoing adjuvant therapy aimed to identify useful informa-tion for the authors’ own country (France). The authors identified a total of 26 stud-ies, of which six met their selection crite-ria. Unfortunately, these six papers were not generalisable to the French health care system, largely because cost data were not sufficiently detailed to allow transparen-cy [8].

A further issue is the financial burden of the costing exercise as resources are usu-ally limited. In terms of actually collecting cost information there are two main ap-proaches, top-down and bottom-up. The top-down approach separates out the rel-evant costs for an intervention from hos-pital or centre annual budgets. The use of such readily available data from routine ac-counts is a low cost approach but could limit transparency and consistency. In con-trast, the more time consuming bottom-up approach identifies all the resources di-rectly employed for an intervention. Such an approach could apparently provide a greater insight into the relationships be-tween activities and their costs, economics of scale of a production process, and the

relative importance of separate activities [9]. In practice many economic evalua-tions combine the two approaches for dif-ferent parts of a study. However, by consid-ering the particular strengths and weak-nesses of these alternative approaches, it may be possible to identify circumstances for their appropriate use.

We report the results of an empirical exercise designed to collect and compare the top-down and bottom-up approaches independently in a multi-centre study. In particular the exercise aimed to discuss the potential for each approach to meet the criteria of consistency and transparen-cy to increase the comparability of cost-ing results. The costing was performed as part of a cost-effectiveness study of di-alysis therapy for end-stage renal disease (ESRD) in ten renal centres across Europe. The European Dialysis and Cost-Effective-ness Study (EURODICE) was funded by the European Commission Biomed 2 ini-tiative with centres in Scotland (two cen-tres), France, The Netherlands, Hungary, Russia, Estonia, Greece (two centres) and Albania. This study built on the results of an earlier Biomed investigation that had demonstrated variations in survival rates across dialysis centres after adjusting for patient variables, such as age, sex and co-morbidities. Amongst the issues to be ex-plored was the impact of resource use on outcome across centres and across differ-ent treatment modalities. It was therefore

38 | Eur J Health Econom 1 · 2005

This procedure requires a permanent cath-eter to be inserted into the abdomen and patients carry out four daily exchanges themselves, at home or at work [].

Dialysis therapy provides a useful ex-ample for comparing costing methods. HD and PD involve different mixes of resources, with HD requiring more staff time and greater use of hospital facilities, whilst PD uses a considerable amount of consumable items. In addition, the range of countries included in this study provid-ed examples of relative cost differences across categories of input, with staff costs, in particular, being much lower in eastern

alysis modalities are haemodialysis (HD) and peritoneal dialysis (PD). HD removes toxic waste and excess fluid from the pa-tient’s via a filter attached to a monitoring machine (artificial kidney). HD is usually performed three times per week with each session lasting around 4 h. Although possi-ble to perform in the patient’s home, HD is more commonly carried out in hospital or a free-standing dialysis centre [0]. In PD the exchange of toxins and fluids occurs across the patient’s semi-permeable peri-toneal membrane. Dialysate (dialysis flu-id) is left in the peritoneal cavity for 4–8 h, drained out and fresh dialysate instilled.

important in this context that costs should reflect differences in resource use as accu-rately and consistently as possible.

End-stage renal disease and dialysis therapy

ESRD is a chronic condition in which in-dividuals have an irreversible loss of kid-ney function. Treatment is by renal replace-ment therapy, comprising dialysis and transplantation. Transplantation is usually favoured; however, limited donor kidneys imply that many patients require long-term or life-long dialysis. The two main di-

Table 1

Annual resource use for dialysis units

Dialysis centre Number of HD sessions

Number of dialysis machines

Total medical staff numbers

Total nursing staff numbers

HD medical staff (WTE)

HD nursing staff (WTE)

Number of PD weeks

PD medical staff (WTE)

PD nursing staff (WTE)

Thessaloniki, Greece 17,002 24 8 32 3.19 20.47 5,242 2.34 3.85

Dundee, Scotland 12,506 17 6 35 0.6 20.66 2,444 0.55 3.24

Veria, Greece 12,088 19 6 25 3.20 14.85 2,288 2.8 2.4

Nantes, France 11,417 23 2 29 1.7 24.65 – – –

Aberdeen, Scotland 10,360 19 10 40 2.17 21.46 1,404 0.71 2.81

Debrecen, Hungary 7,332 21 4 20 3.24 16.2 – – –

Tallinn, Estonia 2,003 8 1 5 0.41 2.51 936 0.08 0.76

Resource information obtained using the bottom-up approach for the year 1999 (WTE whole-time equivalents)

Table 2

Haemodialysis: annual costs per patient

Dialysis centre

Top-down Bottom-up (€) Difference Td-Bu

Including overheads

Excluding overheads

Over- heads as % of total

Including overheads

Excluding overheads

Over- heads as % of total

Including overheads

Excluding overheads

€ Rank € Rank € Rank € Rank € % € %

Dundee, Scotland

35,856 1 29,869 2 17 24,085 3 22,555 2 6 11,771 33 7,314 24

Aberdeen, Scotland

34,381 2 29,491 3 14 25,736 2 24,544 3 5 8,645 25 4,947 17

Nantes, France

32,750 3 30,468 1 7 33,524 1 31,540 1 6 –774 –2 –1,072 –4

Thessaloniki, Greece

23,465 4 21,598 5 8 18,999 5 17,417 5 8 4,466 19 4,181 19

Veria, Greece 23,230 5 21,638 4 7 19,190 4 17,829 4 7 4,040 17 3,809 18

Tallinn, Estonia

12,625 6 11,635 6 8 13,584 6 12,757 6 6 -959 –8 –1,122 –10

Debrecen, Hungary

10,945 7 9,576 7 13 10,223 7 9,243 7 10 722 7 333 3

39Eur J Health Econom 1 · 2005 |

Europe and variations in accounting proce-dures in different health care systems. Dif-ferent costing methods could therefore af-fect the comparisons between modalities as well as between centres and countries.

Methods

The EURODICE costing aimed to calcu-late a cost for a typical HD session and PD week for each study centre. These costs would then be compared with out-comes to develop hypotheses about the re-lationship between resource use and out-comes. Six centres provided both modal-ities and four only HD. The perspective taken was that of the health service in each country. Centre specific resource use and unit cost data were collected on the direct [2] costs for dialysis. Individual patient costing was not possible in this study and the costs are deterministic rather than sto-chastic. Each study centre provided data on the frequency of use of equipment and facilities and on the number of dial-ysis sessions over 2 months. In terms of specific cost categories the different ap-proaches were aiming to collect informa-tion on: staffing (medical, nursing and sup-port staff such as administrative and secre-tarial); consumables (mainly the artificial kidney membranes (dialysers), bloodlines, needles and syringes for HD, dialysis flu-ids for PD and drugs such as erythropoi-etin (anaemia treatment) for both; capital (largely dialysis machines) and overheads (electricity, lighting, heating and medical records etc). The costing for EURODICE was experimental as the top-down and bot-tom-up approaches were performed inde-pendently, as the aim was to compare the process of the approaches as well as the results.

Top-down dialysis costing

This approach aimed to identify, on a com-parable basis, the amount of and cover-age of funding for renal services. The in-formation was largely derived from the re-nal unit accounts, generally held by hospi-tal finance. The approach involved isolat-ing the costs for the two modalities from the entire renal budget and each other. It was anticipated that these internal ac-counts would have been developed using

Abstract

Eur J Health Econom 2005 · 50:38–44DOI 10.1007/s10198-004-0259-9© Springer Medizin Verlag 2005

Sarah Wordsworth · Anne Ludbrook Fergus Caskey · Alison Macleod

Collecting unit cost data in multicentre studies. Creating comparable methods

AbstractInternational comparisons of health care sys-tems and services have created increased interest in the comparability of cost results. This study compared top-down and bottom-up approaches to collecting unit cost da-ta across centres in the context of examin-ing the cost-effectiveness of dialysis thera-py across Europe. The study tested whether health care technologies in different coun-tries can be costed using consistent and transparent methods to increase the com-parability of results. There was more agree-ment across the approaches for peritoneal dialysis than for than haemodialysis, with dif-ferences, respectively of €91–1,687 vs. 333–7,314 per patient per year. Haemodialysis re-sults showed greatest differences where di-alysis units were integrated as part of larg-er hospitals. Deciding which approach to adopt depends largely on the technology. However, bottom-up costing should be con-sidered for technologies with a large compo-nent of staff input or overheads, significant sharing of staff or facilities between tech-nologies or patient groups and health care costing systems which do not routinely allo-cate costs to the intervention level. In these circumstances this costing approach could increase consistency and transparency and hence comparability of cost results.

KeywordsCosting · Multi-centre studies · Dialysis therapy

different systems and in order to under-stand and interpret the relevant account-ing information, a top-down costing ques-tionnaire was designed. This was in the form of statements and specific questions, based on information from meetings of clinicians from all the centres with the study health economists. The question-naire included: (a) the coverage of the re-nal budget, (b) whether the budget identi-fies separate amounts for HD and PD and whether these were on an actual cost basis or allocated from a larger budget, (c) what was included as direct and indirect costs and overheads and (d) allocation meth-ods used to estimate costs. The completed questionnaires were reviewed and areas of uncertainty were clarified on site visits to the study centres during meetings with hospital finance, managers and clinicians (copy available from the authors).

Bottom-up dialysis costing

This approach aimed to obtain detailed cost information at the dialysis unit level. The focus was to identify and quantify spe-cific items used, attach costs and build this up to an entire dialysis session. A bottom-up questionnaire was designed, with a template of resource categories and specif-ic items likely to be used for dialysis. The questionnaire (available from the authors) required completion by dialysis staff (clini-cians, nurses and administrators).

Staff costing for the bottom-up ap-proach was a detailed process. Firstly, infor-mation on the numbers and grades of staff was provided by the questionnaire. Second-ly, all nursing and medical staff estimated the amount of time per week they spent on HD and PD patients with ESRD. Us-ing a prospective time allocation question-naire for the week ahead, any time spent providing treatment to non-ESRD dialy-sis patients was excluded. For capital, if ma-chines were donated, a replacement cost was used based on current manufactur-ers’ prices. Overheads were estimated us-ing the bills from the dialysis units where available. In all other cases costs were ap-portioned from the total for the hospital using a consistent approach based on the floor area of the dialysis unit and then al-located between HD and PD on the basis of activity data. For the bottom-up cost-

40 | Eur J Health Econom 1 · 2005

ing overheads were restricted to items which were essential in providing care for patients, such as heating and power, and which could potentially be saved if the di-alysis unit did not function.

Once items of resource use were identi-fied and quantified, established approach-es were adopted such as local unit costs be-ing applied and the use of equivalent annu-al costing for capital items []. All costs re-late to the year 999 and are converted into euros for presentation. Transport costs were collected, but are not included here because of the variation in who pays for the travel (state, insurance companies or patients). Costs of treating complications

related to dialysis treatment are also not in-cluded in this analysis. In Tirana and St. Pe-tersburg the availability of top-down cost information was limited and in Nijmegen the finance data were too complex to col-lect information independently for the ap-proaches; hence the results are presented for seven centres.

Results

. Table 1 provides quantitative informa-tion on annual dialysis throughput for HD and PD provision across the study centres. The table provides the number of HD ses-sions and PD weeks carried out in each

centre, the number of dialysis machines for HD and the numbers of medical and nursing staff (including whole-time equiv-alent figures) for both. The table highlights that the centres vary in the labour produc-tivity devoted to dialysis. However, a com-mon theme is that HD tends to be a nurse intensive activity, with PD assuming slight-ly more medical staff time than for HD.

. Table 2 presents the results of the an-nual costs per patient based on the alterna-tive costing approaches for HD including and excluding overheads, as we anticipat-ed that overheads could be different with the two approaches. The results show that for HD the absolute differences between the two approaches per patient per annum, range from €722 (Debrecen, Hungary) to €,77 (Dundee, Scotland) including over-heads and from €333 (Debrecen) to €7,34 (Dundee). In percentage terms the largest differences are also for Dundee, whilst the smallest absolute differences are for Nantes (including overheads) and Debre-cen. In comparing the costs across centres Dundee appears to be the most expensive using the top-down approach and includ-ing overheads, but Nantes is the most ex-pensive when overheads are excluded or bottom-up costing is used.

The table highlights a division between dialysis units that are closely integrated as part of larger hospitals and others that are not. Specifically, the Scottish and Greek di-alysis units are based in hospitals where renal services, including dialysis for acute renal failure, are provided together. In ad-

Table 3

Peritoneal dialysis: Annual costs per patient

Dialysis cen-tre

Top-down (€) Bottom-up (€) Difference A-B

Including overheads

Excluding overheads

Over-heads as % of total

Including overheads

Excluding overheads

Over-heads as % of total

Including overheads

Excluding overheads

€ Rank € Rank € Rank € Rank € % € %

Thessaloniki, Greece

28,027 1 27,848 1 1 26,313 2 26,162 2 1 1,714 6 1,686 6

Veria, Greece 27,785 2 27,646 2 1 26,552 1 26,434 1 <1 1,233 4 1,212 4

Aberdeen, Scotland

23,731 3 22,434 3 5 22,734 3 22,343 3 2 997 4 91 0.4

Tallinn, Estonia

21,626 4 21,400 4 1 20,728 4 20,581 4 1 898 4 819 4

Dundee, Scotland

19,829 5 18,603 5 6 18,412 5 17,625 5 4 1,417 7 1,078 10

Table 4

Cost difference (euros) by modality: Annual costs per patient; figures include overhead costs

Dialysis centre Haemodialysis Peritoneal dialysis Difference (A-B)

Aberdeen, Scotland• Top-down• Bottom-up

34,38125,736

23,73122,734

10,650 3,002

Dundee, Scotland• Top-down• Bottom-up

35,85624,085

19,82918,412

16,027 5,673

Thessaloniki, Greece• Top-down• Bottom-up

23,46518,999

28,02726,313

–4,562–7,314

Veria, Greece• Top-down• Bottom-up

23,23019,190

27,78526,552

–4,555–7,362

Tallinn,Estonia• Top-down• Bottom-up

12,62513,584

21,62620,728

–9,001–7,144

41Eur J Health Econom 1 · 2005 |

dition, dialysis staff may care for patients with other renal and non-renal conditions. These hospitals have common services, such as radiology, which are not attribut-ed to the dialysis unit specifically. In con-trast, Nantes is a free-standing unit only providing HD for chronic ESRD (acute re-nal failure patients are dialysed elsewhere). In Tallinn and Debrecen, whilst both units are based on hospital sites, they operate fairly independently. Essentially, the more independent the unit, the less the differ-ence between the costing approaches.

The extent to which overheads con-tribute to the total costs varies between the two costing approaches and, for the top-down method, reflects differences in finance systems between the centres. As a percentage of total cost overheads range from 7% to 7% in the top-down approach and from 5% to 0% in the bottom-up cost-ing. The largest reductions in percentage overheads occur for those centres with high overheads in the top-down approach and the narrower range in the bottom-up approach may reflect greater consistency in the costing method. However, the size of the difference in the costing approach-es is not explained by the inclusion or ex-clusion of overheads for the Greek centres and is only partially explained for the Scot-tish centres.

There was a smaller difference between top-down and bottom-up costs for PD than for HD and less difference between costs with and without overheads (. Ta-

ble 3). Here the differences per patient per annum ranged from €898 (Tallinn) to €74 (Thessaloniki) when overheads were included and €9 (Aberdeen) to €,687 (Thessaloniki) excluding overheads. A far greater proportion of the total cost of PD is accounted for by consumables. Dialysis units based in larger hospitals providing a whole range of services showed some ten-dency towards larger differences in cost, but this was not as marked as for HD. This is not unexpected, given that the propor-tion of total hospital based care is small for PD compared with HD. Aberdeen and Dundee had higher overheads as a percent-age of total costs but again this was not as great as for HD. With PD there is gener-ally greater stability with centre rankings, although the two Greek centres change rankings between first and second with the costing approaches, this represents a small monetary difference.

In terms of whether using the differ-ent approaches could influence decision making, comparing centres with differ-ent results from the two approaches is important (. Table 4). This time includ-ing overhead costs, Tallinn revealed one of the smallest differences using the two approaches for both treatment modali-ties, with top-down costs being €959 low-er for HD and €998 higher for PD than bottom-up. This was smaller than the cost difference between the treatment modali-ties; hence this did not alter the direction or have a substantial impact on the mag-

nitude of the cost difference between HD and PD. In Aberdeen and Dundee, howev-er, the use of top-down costing produces around a threefold increase in the cost dif-ference between modalities. HD is €0,650 more expensive than PD using top-down methods compared with a difference of €3,002 for bottom-up costing in Aberdeen (figures for Dundee are €6,027 and €5,673, respectively). Thus top-down costing may potentially exaggerate the cost advantage of PD. Interestingly, for the Greek centres, where PD is the more costly modality, the effect of the difference between top-down and bottom-up costing works in the oppo-site direction.

To determine the source of the differ-ences across the two approaches the cate-gories of costs were examined. . Table 5 compares eastern (Tallinn) and western (Aberdeen) European centre cost category breakdowns for both modalities. The per-centage contribution to the total cost, abso-lute cost difference between the costing ap-proaches and the difference in percentage contribution to total cost are shown for staff, consumables, capital and overheads.

When comparing the distribution of costs across categories in these centres, staff costs form a much larger compo-nent of total HD costs in Aberdeen. Over-heads are also higher in the top-down cost-ing, and both of these items are important drivers of the difference in cost between the two approaches. The process of iden-tifying staff costs for the bottom-up ap-

Table 5

Comparing unit costing approaches by input category, Aberdeen and Tallinn: annual cost per patient for haemodialysis and peritoneal dialysis in euros and as percentage of total costs

Haemodialysis Peritoneal dialysis

Top-down Bottom-up Difference Top-down Bottom-up Difference

€ % € % € % € % € % € %

Aberdeen, Scotland• Staff• Consumables• Capital• Overheads• Total

16,03511,995 1,461 4,89034,381

4735 414 –

12,61710,386 1,542 1,19225,736

4940 6 5 –

3,4181,609 –813,6988,645

40 19 –1 43 –

6,68615,748 0 1,29723,731

2866 – 5

2,74119,486 116 39122,734

1286 1 2 –

3,945–3,738 –116 906 997

396–375 –12 91 –

Tallinn, Estonia• Staff• Consumables• Capital• Overheads• Total

949 8,495 2,191 99012,625

86717 8 –

1,060 8,883 2,814 82713,584

86521 6 –

–111 –388 –623 163 –959

–12–40–65 17 –

92720,473 0 22621,626

495 – 1 –

20020,351 30 14720,728

198 – 1 –

727 122 –30 79 898

81 14 –3 –9 –

42 | Eur J Health Econom 1 · 2005

Original Papers

proach not only excludes time unrelated to patient care but also allocates out time spent with patients not receiving dialysis care. This was an important factor in units not exclusively providing dialysis care. In Tallinn capital costs are more significant in driving the comparatively small difference between the approaches. Overall Aberdeen shows a much greater difference between the methods in absolute terms than does Tallinn (€8,645 compared with €959).

For PD the absolute differences in cost between the two methods were small in both centres (€997 in Aberdeen, €898 in Tallinn). However, in Aberdeen this was the result of relatively large and opposite differences in staff and consumables costs cancelling each other out. In Tallinn the difference was mainly due to staff costs. In both centres staff costs revealed propor-tionately large differences between the two approaches. Aberdeen also had a large dif-ference in consumable costs, which is part-ly explained by the fact that some patients were receiving a relatively expensive drug, erythropoietin, from their general practi-tioners rather than the dialysis unit, and hence this cost was excluded from the top-down information for some patients. With respect to capital costs both centres had top-down PD information missing, as patients use shared capital items, such as weighing scales, which tend not to be

purchased specifically for PD but which were identified through the bottom-up ap-proach.

Issues relating to the comparison of top-down and bottom-up

. Table 6 highlights specific issues relat-ing to the comparison of the costing ap-proaches. Predictably, information was easier to obtain using the bottom-up ap-proach, which also provided more detailed data. Information using the top-down ap-proach was often more difficult to obtain and less detailed than we required. Al-though the exceptions were Nantes and Tallinn where detailed budget requests were submitted to social health insurance companies; hence finance information needed to be detailed and robust.

The level of detail obtained on specif-ic dialysis inputs with the bottom-up ap-proach was particularly important for in-terpreting the costing results and cost dif-ferences arising from treatment policies of the centres. Some of these policy dif-ferences are unlikely to have a significant impact on the costing while others have the potential to make a substantial impact. Four treatment policies were identified as being potentially important for the cost-ing and possibly clinical outcomes: (a) re-use of dialysers (artificial kidneys), rather

Table 6

Comparing the top-down and bottom-up approaches to specific issues

Category Top-down Bottom-up

Availability of information

Quite difficult to obtain and interpret in most centres, as data collected and summarised for hospital accounting. Plus systems and reporting varied.

Information fairly straightforward to obtain as study team controlled data collection.

Coverage Information minimal in some areas, extensive in others. Coverage of costs controlled by standardised questionnaires.

Approaches to specific costs

Information on whole-time equivalent staff readily available, but not separated from acute dialysis, transplantation or general medicine and not divided into HD and PD.Overhead allocation unclear in some centres. Scope of overheads and allocation to dialysis varied.

Staff cost information fairly time consuming, with the collection and analysis of time allocation questionnaires. However, the information was rich and transparent.Where available actual overhead costs incurred by dialysis used. Otherwise overhead costs for entire hospital allocated to dialysis by floor space and to HD and PD on activity basis.

Identification of volume and mix

Generally provided total spending under specific headings, making it difficult to establish whether centre cost differences due to volume and mix of resources or price differences.

Allowed for separation between volume and mix of resources, helping explain centre cost differences.

Cost differences relating to centre treatment policies

Difficult to identify. Able to identify.

than disposing of them after each dialysis session, (b) administration of iron to dial-ysis patients differed between centres, (c) the number of dialysis sessions per week (this was similar for most of the centres, usually 4 h sessions three times per week, but in one centre almost 50% of patients were having only two HD sessions per week) and (d) the mix of staff in the dialy-sis units and allocation of tasks. In one cen-tre a consultant nephrologist performed a large share of the administrative tasks. In other centres a senior nurse or full time re-nal administrator was responsible for sim-ilar administrative work.

In Dundee, the bottom-up data high-lighted that dialysers were being re-used, whereas other centres used a new dialyser for each session. This reuse policy created additional costs for staff and capital, yet sav-ings on consumables. However, this saving was offset in the total cost by the same cen-tre administering iron to its patients intra-venously rather than orally, which was the practice in the other centres. Neither policy was apparent in the top-down information, even though they could influence key clini-cal outcomes such as haemoglobin values.

Discussion and conclusions

We report the results here of a methodolog-ical exercise to compare the top-down and

43Eur J Health Econom 1 · 2005 |

bottom-up methods for collecting unit cost data from centres in different coun-tries to increase comparability of results. The results revealed that in some centres the total annual costs per patient were sim-ilar across the two approaches; however, other centres had fairly large differences. The centres which reported the greatest dif-ferences were closely integrated within a larger hospital and staff did not work ex-clusively with dialysis patients. In terms of the two dialysis modalities there was more agreement across the approaches for PD rather than HD.

Overall the bottom-up approach pro-vided greater consistency and transparen-cy, as might be expected with an approach using standardised methods and detailed information on the constituents of the cost. However, there is an obvious trade-off between data richness and the time and resources required to collect bottom-up information. This study also identified the main cost drivers so that future dialy-sis costings could be performed using less research resources and piloting of the bot-tom-up approach is advocated for other areas.

The decision about which approach to adopt generally, or which approach to adopt for specific cost categories, will be largely dependent on the health care tech-nology in question. The results from our methodological exercise suggest that a technology where consumables are like-ly to form the largest component of re-sources is unlikely to produce substantial-ly different results regardless of which ap-proach is adopted. The three main factors that would indicate that bottom-up cost-ing should be considered are technologies with a significant component of staff input or overheads, significant sharing of staff or facilities between technologies or patient groups and health care costing systems which do not routinely allocate costs to the level of particular interventions. In these circumstances a bottom-up approach to in-crease the level of detail in the costing and hence comparability.

In conclusion, the approach taken to collecting cost data can affect the results of economic evaluations, particularly where the input mix varies substantially. The significance of this issue will be great-est where there are large variations in

how budgets, particularly top-down bud-gets, are formed. In terms of policy impli-cations from this study, when different di-alysis centres are compared on broad in-dicators of costs or outcomes there may be insufficient information to draw robust conclusions. If a centre has better clinical outcomes, it is important to determine the extent to which this reflects increased re-source availability, more efficient use of resources, and differences in policies and practices for dialysis. There is a greater vari-ation in the results of top-down costing re-flecting in the main the degree to which a hospital divides its services for budgeting. The more each unit is segregated for bud-getary purposes the more the top-down and bottom-up costing figures resemble each other. Finally, when comparing ser-vices in different countries and relating the results to clinical outcomes, it may be helpful to use the bottom-up approach.

Corresponding authorSarah Wordsworth

Health Economics Research Centre, University of Oxford, UK e-mail: sarah.wordsworth@dphpc.ox.ac.uk

Acknowledgements

Funding from the Biomed 2 programme of the European Commission is acknowledged. The Health Economics Research Unit (HERU) is funded by the Chief Scientist Office of the Scottish Executive Health Department (SEHD). The views expressed in this contribution are those of the au-thors and are not attributable to either funding body. We thank the other members of the EURODICE study for support with data collection and to anonymous referees for their comments.

Conflict of interest: No information supplied

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Original Papers