Evidence-based health care management © ltarcourt Brace and Company Ltd 1998

A computerized decision-support system helped trainee doctors control the dosage of an oral anticoagulant

Vadher B, Patterson D L H, Leaning M. Evahtation o f a decision support system for initiation and control o f oral anticoagulation ht a randomised trial. BMJ 1997; 314:1252-1256

Background

The debates about general computerized decision support are common but unenlightening; its contribution has to be evaluated in each specific context.

Objective

To determine the safety and effectiveness of a computerized decision tool for aiding trainee doctors in determining the correct dosage of an oral anticoagulant, warfarin.

Setting

District general hospital in north London.

Method

Randomized, controlled trial. 72 patients, 76 control.

The subjects were 148 inpatients at the Whittington Hospital who required treatment with warfarin.

Literature review

None stated; 24 references.

Outcomes

1. Median time to achieving dosage within therapeutic range

2. Time to stable dose 3. Time to first excessive dosage after

therapeutic range achieved 4. Person-time spent in therapeutic range.

Results

Median time to reaching therapeutic range was not significantly improved by the intervention. However, the other critical outcomes, including median time to reaching a stable dose, median time to a departure from therapeutic range (over- or undertreatment), and person-time in therapeutic range, were significantly improved by the use of the computerized decision aid.

Authors' conclusions

The computerized decision support was safe and effective and improved the quality of initiation and control of warfarin treatment by trainee doctors.

:O.M M ENTAR~

Will using this t-2chnology bring significant improvements in health? If the answer is "yes,' then we should consider diverting scarce resources towards it. But equally important is the question of whether the innovation will allow us to deliver the same quality of care at lower cost. We need to consider both these arguments when reading this paper on computer support for anticoagulant monitoring.

The casual reader might be disappointed that there were no major health gains for patients when their doctors used computer support to determine the warfarin dose. Thromboembolism and haemorrhage were just as common in the intervention and control groups and there were similar numbers of deaths. These adverse events are fortunately rare. A study of over 1000 patients would be needed to demonstrate a doubling of the haemorrhage rate, about 10 times the size of the currently reported study. Such large studies of the effects of computer support for drug dosage have not yet been performed so we must look to smaller studies that point to potential benefit.

Vadher et al have shown that computer support for dosage protects patients from the dangers of under- or overdose with warfarin. This finding is confirmed by earlier work. in a study of 75 patients, the time spent with a therapeutic prothrombin time rose from 36 to 56 days with computer support (effect size 0.78, 95% £1 0.31-1.25). I Similar

improvements were seen by the same group in a later study 2 and have been confirmed both in primary and secondary care. 3.4 It seems reasonable to assume that improved control will lead to fewer unwanted events although, as yet, we have no concrete evidence that this is the case.

If we are convinced, at least, that computer support has no deleterious effects on health outcomes, is there an opportunity to provide the same level of care at lower cost? The current paper suggests that therapeutic levels were achieved more quickly with computer support. The largest previous study also showed this effect and demonstrated that computer support reduced hospital stays from 20-13.4 days (effect size 0.60, 95% Cl 0.13 to 1.1)? This benefit is confirmed in studies of computer support in other specialties, s-7 Other studies on warfarin control have shown that a reduced number of blood tests are needed when computer support is used. 1.3,s Reduced time in hospital and fewer blood tests are outcomes valued by patients, doctors and purchasers alike.

Formal economic evaluation in a large randomized controlled trial would give the information we need to make an evidence- based purchasing decision. But the evidence we already have is compelling.

References

1. White R H, Hong R, Venook A Pet al. Initiation of warfarin therapy: comparison of physician dosing with computer-assisted dosing. J Gen Intern Med 1987; 2:141-148

2. White R H, Mungall D. Outpatient management of warfarin therapy: comparison of computer-predicted dosage adjustment to skilled professional care. Ther Drug Monit 1991; 13:46-50

3. Fitzmaurice D et al. Evaluation of computerized decision support for oral anticoagulation management based in primary care. Br J Gen Pract 46:533-535

4. Abbrecht P, O'Leary T, Behrendt D. Evaluation of a computer-assisted method for individualized anticoagulation: retrospective and prospective studies with a pharmacodynamic model. Clin Pharmacol Ther 1982; 32:129-136

5. Burton M E, Ash C L, Hill D P Jr, Handy 1, Shepherd M D, Basko M R. A controlled trial of the cost benefit of computerized bayesian aminoglycoside administration. Clin Pharmacol Ther t 991; 49:685-694

6. Destache C J, Meyer S K, Rowley K M. Does accepting pharmacokinetic recommendations impact hospitalization? A cost-benefit analysis. Ther Drug Monit 1990; 12:427-433

7. Hurley S F, Dziokas L J, McNeil J J, Brignell M J. A randomized controlled clinical trial of pharmacokinetic theophylline dosing. Am Rev Respir Dis 1986; 1345:1219-1224

8. Fihn S D et al. A computerized intervention to improve timing of outpatient fol[ow-up: a multicenter randomized trial in patients treated with warfarin. National Consortium of Anticoagulation Clinics. J Gen Intern Med 1994; 9:131-139

Dr Robert Walton Bury Knowle Health Centre

Oxford, UK

JUNE 1998 EVIDENCE-BASED HEALTH POLICY AND MANAGEMENT 47