Surgical stabilisation of the spine compared with a programme of intensive rehabilitation for the management of patients with chronic low back pain: cost utility analysis based on a randomised controlled trial

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Appendix

Additional detail of the costing methods

Resource use

Patient-specific NHS resource use data collected included: initial treatments i.e. surgery or rehabilitation, other back pain related hospital inpatient and outpatient visits, primary care contacts, and numbers of prescribed items of medication. Data were also collected on over the counter medications purchased by patients for back pain and any related visits made to private practitioners. Protocol driven resource use such as trial follow-up assessments was excluded from the analysis. The number of centres participating in the trial and constraints on resources precluded the collection of centre specific unit costs. Where possible, national average costs were used and supplemented by costs from the lead-investigating centre. All costs calculated and presented are expressed in 2002/2003 £UK with prices inflated to this base using the Hospital and Community Health Service Inflation Index where appropriate.^w1

Spinal Fusion Surgery

A ‘micro’ approach to the costing of surgery used patient specific itemised resource use data collected during the trial. The duration (in minutes) spent by each patient in the operating theatre was collected using surgeon record sheets. A published cost per hour for an empty theatre (inclusive of hospital overheads, building charges, and routine theatre capital equipment) was applied to these data to estimate the cost associated with use of the theatre per se^w2. Information on medical personnel present during each patient’s surgery was also documented, and their time in theatre costed by applying relevant staff costs per minute, calculated using the mid-point from appropriate annual salary scales (inclusive of employers’ National Insurance and pension contributions).^w1

Types and numbers of surgical implants inserted were recorded and valued using unit costs (inclusive of hospital discounts and VAT) obtained from the lead-investigating centre. Any intra-operative spinal X-rays were costed so as to include the cost of the X-ray per se (obtained from the lead centre) and 30 minutes of radiographer time (again costed by using the mid-point of an appropriate salary scale to generate a staff cost per minute).^w1 Use in theatre of image intensifying capital equipment was also recorded (in minutes) for each patient. An equivalent annual cost for this equipment was calculated using the purchase price and assuming a useful life of ten years and a discount rate of 5%. Dividing this figure by anticipated annual hours of use produced an equipment cost per minute, which was then applied to the appropriate resource use data.

An anaesthetics sheet completed for each patient provided information on inhalational anaesthetic agents administered during each patient’s surgery. Unit costs for such drugs (inclusive of hospital discounts, VAT and pharmacy overheads) were provided by the lead-investigating centre and were used within the conventional formula for calculating the cost of anaesthetic vapours.^w3 Costs of disposable items (inclusive of VAT) used in the administration and monitoring of anaesthesia were also obtained from the lead-investigating centre. Any blood products given to patients during surgery were valued using unit costs (inflated for blood bank handling charges) obtained from the National Blood Service, and the costs of any surgical complications were assumed to be reflected in the duration spent by the patient in theatre. Methods for post-operative pain control were documented and costed accordingly.

Information on each patient’s surgery-related inpatient hospital stay was obtained from routine hospital information systems, and costed by applying a national average cost per bed day for an orthopaedic ward.^w4

Intensive Rehabilitation

For each patient, information was collected on the number of half-day rehabilitation sessions attended. Observed programme staffing requirements, patient throughput data, and appropriate salaries (inclusive of employers’ National Insurance and pension contributions) were used to generate an estimate of the staffing costs per half-day session.^w1 Patients underwent one hydrotherapy session per day, a cost for which was obtained from the lead-investigating centre. Exercise equipment comprised one chair and one exercise mat per patient. Equivalent annual costs for these were calculated based on purchase prices provided by the lead centre and assuming a useful life or two years and a discount rate of 5%. Dividing this cost through by observed patient throughput data generated an equipment cost per half-day session. Use of the hospital gym and a meeting room were costed by adding 15% (the overhead rate employed by the lead centre) to the staff, hydrotherapy and equipment costs. Finally, overnight accommodation at either a private Bed and Breakfast (paid for by the NHS) or on a hospital ward was documented. Unit costs for Bed and Breakfast stays were obtained from the lead-investigating centre, whilst ward ‘hotel costs’ were obtained from the Department of Health.^w5

Other Back Pain Related NHS Contacts

At six, 12 and 24 months patients used postal questionnaires to report hospital outpatient clinic attendances relating to spinal surgery, physiotherapy, and other back pain related care. Unit costs for surgery and physiotherapy attendances were obtained from the Trust Financial Returns Database^w4, and other back pain related attendances were costed according to reason specified, using a variety of sources.^w1,w6-7 Reasons for and dates of inpatient hospital admissions related to back pain were also documented. Admissions for unplanned spinal fusion surgeries were costed using the overall mean cost of a fusion procedure (calculated as described above), plus the cost of a patient’s inpatient length of stay on an orthopaedic ward.^w4 Overnight admissions for investigations or assessments, included the cost of the evaluative procedure (provided by the radiology department of the lead-investigating centre) plus hotel costs incurred by an overnight stay on a general medical ward.^w5 Patients reported visits to and home visits from GPs and practice nurses. Unit costs applied to these contacts were obtained from Netten and Curtis.^w1 Finally any additional attendances at intensive rehabilitation programmes were recorded and costed using the average cost of attending a three-week course of rehabilitation (calculated as described above).

Patients Costs

Patients reported back-pain related contacts with private complementary practitioners and unit costs were obtained from the relevant national organisations. Patients also documented numbers of items of medication they had been prescribed, and how much they had paid for any over the counter medication purchased for back pain.

References

^w1 Netten A, Curtis L. Unit costs of health and social care. Canterbury: Personal Social Services Research Unit, University of Kent at Canterbury, 2003.

^w2 MASS Group. Multicentre Aneurysm Screening Study (MASS): Cost-effectiveness Analysis of Screening for Abdominal Aortic Aneurysms Based on Four Year Results from a Randomised Controlled Trial. BMJ 2002;325:1135-41.

^w3 Dion P. The cost of anaesthetic vapours. Canadian Journal of Anaesthesia; Journal Canadien d'Anesthesie 1992;39:633.

^w4 Chartered Institute of Public Finance and Accountancy. The health service financial database and comparative tool. Croydon: Institute of Public Finance, 2000.

^w5 Mallender Hancock Associates (MHA). National Average Specialty treatment and Hotel Costs. London: Department of Health, 1998.

^w6 Information Services Division NHS Scotland. The Cost Book 2003.http://www.isdscotland.org/isd/info3.jsp?p_service=Content.show&pContentID=360&p_applic=CCC& (accessed July 2004).

^w7 Department of Health. NHS Reference Costs 2003. Wetherby: Department of Health, 2004.

Posted as supplied by author.

Participating units: Woodend Hospital, Aberdeen: J Burt, J. Easton, M Stocker, D Wardlaw; BUPA Hartswood Hospital, Brentwood: E Gampell, A Gardner; Hinchingbrooke Hospital, Huntingdon: A Taylor, A Wojcik; The Ipswich Hospital, Ipswich: A Garner, J Gooderham, J Powell, D Sharp, H Vernau, J Wright; Middlesbrough General Hospital, Middlesbrough: C Greenough, A. Jones, S. Nicholson, S Papastefanou, A Wilkin; Queen’s Medical Centre, Nottingham; E Bevan-Davies, B Freeman, R. Goodwin, M Grevitt, J Hegarty, R Kasim, S Mehdian, R Mulholland, H Prince, A Wainwright, J Webb; Robert Jones & Agnes Hunt Orthopaedic Hospital, Oswestry: C Darley, S Eisenstein, C Evans, E Jones; Nuffield Orthopaedic Centre, Oxford: A Allen, K Barker, J Fairbank, B Swietalska, J Wilson-MacDonald; Royal Berkshire Hospital, Reading: R Marshall, A Sandall; St. Albans City Hospital, St.Albans: S Crowley, P Dyson, S Harvey, E McWhirter; Northern General Hospital, Sheffield: J Getty, K Grafton, K Jones, L Yorke; Royal National Orthopaedic Hospital, Stanmore: J Johnson, H Nafis, M Sullivan; North Staffordshire Hospital, Stoke-on-Trent: J Dove, G Evans, V Jasani; Sunderland Royal Hospital, Sunderland: A Cross, G Gatenby; Princess Margaret Hospital, Swindon: F. Cook, A Fogg, M Foy, J Hay

The MRC Steering Committee included R Collins, J Fairbank, H Frost, W Gillespie (first chairman), A Grant, A Gray, P Gregg (second chairman), M Jayson, R Johnstone, J Klaber-Moffett, and W Maton-Howarth.