|Evaluation of an alternative model of anticoagulant care
|Hennessy B J, Vyas M, Duncan B, Allard S A
This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn.
Introduction of a nurse specialist supervised, computer assisted warfarin-dosing system (CDSS) in the delivery of anticoagulant care. The nurse-led service operates as follows: on starting warfarin patients are counselled for approximately 25 minutes by the nurse specialist before being reviewed by the doctor. The nurse specialist then follows them up in the return clinic until their international normalised ratio (INR) is stable. Patients who are experiencing problems with their anticoagulant control or who are due to stop warfarin for surgical treatment are also reviewed in the return clinic. Once stabilised on warfarin patients attend the phlebotomy clinic at their convenience and leave their 'yellow' anticoagulant therapy record books with their samples. The book is then returned by post with dosage instructions. Patients are phoned the same day if the dose of warfarin needs to be adjusted. Samples taken at home and in general practice surgeries are also dealt with in this way.
Economic study type
Patients requiring anticoagulant care.
Hospital and community. The economic analysis was carried out in London, UK.
Dates to which data relate
Effectiveness and resource use data corresponded to patients treated in the study institution between 1994 and 1998; two six-month periods, two years apart, before and after the introduction of the nurse-led delivery service. The price year was not explicitly specified.
Source of effectiveness data
Effectiveness data were derived from a single study.
Link between effectiveness and cost data
Costing was conducted retrospectively on the same patient sample as that used in the effectiveness analysis.
Power calculations were not used to determine the sample size. Over the study period (1995-97), the number of patients in the service increased by 43% from 818 to 1,170. At the time of the study, 2,520 patients were registered; of whom 1,610 were on anticoagulants, 1,498 being on lifelong treatment. The total number of visits in a six-month period before the introduction of the nurse-led service (consultant-led service period) was 3,902 versus 5,086 over a six-month period after the introduction of the nurse-led service. A patient questionnaire was completed by 137 patients (6% aged over 66 years, 92% aged over 46 years) who used the nurse-led service.
This was a retrospective cohort study, carried out in a single centre. Patient re-attendance intervals were 4 and 8 weeks. Loss to follow-up was not reported. The information for the consultant-led group was based on laboratory log books and patient anticoagulant summary sheets, while the information for the nurse-led group was obtained from computerised records held in the Dawn AC system. Data about patients' education and satisfaction from the new type of care were collected prospectively through questionnaires, given to patients presenting for phlebotomy over a two-week period in November 1998.
Analysis of effectiveness
The principle (intention to treat or treatment completers only) used in the analysis of effectiveness was not explicitly specified. The health outcomes were number of patients managed by flexible walk-in postal system, appointment intervals to the nearest week, anticoagulant control (as determined by assigning INR results in the following ranges: less than 2.0, 2.0 to 3.0, 3.1 to 4.5, and greater than 4.5), and complications. A patient questionnaire was also completed to assess patient satisfaction and education with CDSS. The questionnaire was designed using Formic, an optical character recognition package and consisted of simple questions with answers given as options in a tick box format. The comparability of patient baseline characteristics in the two study groups was not investigated.
Despite an increase of 43% in the number of patients in the service, the average attendance at fixed anticoagulant clinics has reduced by 48%, from 77 to 49 over the two-year study period (1995-1997).
The proportion attending flexible 'walk-in' clinics increased by 50% from 51% to 76%.
The average appointment interval remained at 4 weeks and the percentage attending at the maximal eight weeks interval increased from 3% to 15%.
The percentage in the consultant- and nurse-led services in the therapeutic range (INR 2 to 4.5) was similar at 75.2% versus 74.6%.
The proportion of patients under-anticoagulated (INR less than 2.0) was the same, 22.9% versus 23.5% and over-anticoagulated (INR greater than 4.5) 1.9% versus 1.9%.
There was no difference in complications between the groups. Patient knowledge and satisfaction scores were high on the questionnaire.
This study confirms that the levels of anticoagulant control are similar between the two types of service, with an overall improvement in the quality of the service despite an increase in numbers.
Measure of benefits used in the economic analysis
No summary benefit measure was identified in the economic analysis, and only separate clinical outcomes were reported.
Costs were not discounted due to the short time frame of the cost analysis. Some quantities were reported separately from the costs. Cost items were reported separately. Cost analysis covered the initial costs of the computer system and its annual maintenance, nurse's time, consultant's time, registrar's time, INR test, and transport to return clinics. The perspective adopted in the cost analysis appears to have been that of the UK National Health Service (NHS). Salaries were taken as the mid-point of the appropriate NHS salary scales. Additional benefits and (on call) costs were not incorporated in the salaries.
Estimated benefits used in the economic analysis
The average total cost attributable to each service delivery method was not reported; instead the following information was given: 5,000 for the initial cost of the computer system with an annual maintenance cost of 500. The nurse specialist salary was 21,000. Annual cost reductions in consultant and registrar's time was 13,000; reduction in transport cost to return clinics of 5,000; reduction in INR test costs (25 per 10 tests); reduction in frequency of testing, and the reduction in clinic size.
Synthesis of costs and benefits
Costs and benefits were not combined.
The introduction of a nurse specialist managed service has allowed the study institution to accommodate a 21% annual increase in patient numbers while improving the overall quality, efficiency, and cost-effectiveness of the service and patient care.
CRD COMMENTARY - Selection of comparators
A justification was given for the choice of the comparator (a consultant-led delivery service). It was the previous method used in the study institution. You, as a database user, should consider whether this is a widely used delivery method in your own setting.
Validity of estimate of measure of effectiveness
The internal validity of the effectiveness results can not be guaranteed due to the retrospective nature of the study design, and lack of investigation of comparability of the study groups. The number of patients in each study group and the procedures followed to select patients retrospectively was not clearly specified. Insufficient information was provided regarding the patient characteristics; as a result it is not possible to assess whether the study sample was representative of the study population.
Validity of estimate of measure of benefit
The authors did not derive a measure of health benefit. The study may therefore be regarded as a cost-consequences analysis.
Validity of estimate of costs
Some quantities were reported separately from the costs. Adequate details of methods of cost estimation were not given. The price year was not specified. The retrospective nature of the cost calculations introduces the possibility of bias. The costs of telephone calls and mail appears not to have been included in the cost analysis introducing the possibility of further bias. The effects of alternative procedures on indirect costs were not addressed. No statistical analyses were performed on resource use or cost data. The average total cost attributable to each service method was not calculated. The cost results may not be generalisable to other settings.
In view of the retrospective nature of the study design, lack of sensitivity analysis, and statistical analysis of resource use and costs, the study results should be interpreted with some degree of caution. The issue of generalisability to other settings was not addressed, although some comparisons were made with other studies. It was reported that decentralised anticoagulant care with varying levels of improvement by general practitioners is an alternative model to the nurse-led CDSS.
Implications of the study
Caution and careful patient selection in any anticoagulant care delivery methods are advisable.
Hennessy B J, Vyas M, Duncan B, Allard S A. Evaluation of an alternative model of anticoagulant care. Irish Journal of Medical Science 2000; 169(1): 34-36
Subject indexing assigned by NLM
Aged; Anticoagulants /administration & England; Evaluation Studies as Topic; Hospital Restructuring; Humans; Medication Systems, Hospital /organization & Middle Aged; Models, Organizational; Nurses; Outpatient Clinics, Hospital /organization & Warfarin /administration & administration; administration; dosage; dosage
Date bibliographic record published
Date abstract record published