Volume 176 - Issue 4
PBS/RPBS cost implications of trends and guideline recommendations in the pharmacological management of hypertension
Authors: Ben D Ewald and Brita A Pekarsky
Med J Aust 2002; 176 (4): 189-190. || doi: 10.5694/j.1326-5377.2002.tb04357.x
Published online: 18 February 2002
Published online: 18 February 2002
To the Editor: The article by Nelson et al1 estimates Pharmaceutical Benefits Scheme and Repatriation Pharmaceutical Benefits Scheme (PBS/RPBS) savings if hypertensive patients on monotherapy were prescribed the agents recommended in guidelines; however, the analysis contains algebraic errors and insufficient sensitivity analyses. The question of excessive costs through the use of expensive agents for which there is no evidence of increased benefit for most patients is an important one, but the estimates of extent of overuse should be methodologically sound. The three main concerns we have with the paper's estimates are as follows:
The total number of patients on monotherapy in Box 3 of the article adds to 1.1 million, whereas elsewhere the authors state that 60% of all 1.2 million Australian patients treated for hypertension are on monotherapy, giving an estimate of 0.72 million. (These estimates of 60% and 1.2 million are not referenced in the article.) One reason for this discrepancy is that the authors have treated the sum of column 4 in Box 2 as patients, not patient-years of treatment (some patients are on dual or triple therapy), leading to a 40% overestimate of numbers of patients on monotherapy reported in Box 3.
Utilisation of prescription drugs is recorded by PBS/RPBS only if the cost to patient is subsidised. Therefore, PBS/RPBS expenditure divided by total patient numbers (Box 2) underestimates consumer cost for diuretics and β-blockers, both of which cost less than the non-concessional co-payment. Of total PBS/RPBS scripts, 16% are for non-cardholders,2 and the cost per script to these patients is about three to four times the prevailing 1998 cardholder co-payment. As a rough estimate, total consumer cost for these agents may need to be doubled, and their omission is therefore material. Although non-concessional patients still have a saving, it is less than that estimated in the article.
Sensitivity analysis should have been performed on the following critical assumptions: (1) proportion of use for hypertension for each class of drugs, (2) the number of unsubsidised users of diuretics and β-blockers, and (3) the proportion of patients on each agent who are on monotherapy.
It is vital that the current scrutiny by all stakeholders of PBS/RPBS expenditure be informed by reasonable estimates of inappropriate utilisation. The contribution made by the authors in developing a technique to estimate appropriate use for this group of drugs is valuable. However, use of unreferenced estimates of key variables, insufficient application of sensitivity analyses, algebraic errors and inappropriately combining PBS with non-PBS data may cloud rather than shed light on this issue.
References
- Nelson MR, McNeil JJ, Peeters A, et al. PBS/RPBS cost implications of trends and guideline recommendations in the pharmacological management of hypertension in Australia, 1994–1998. Med J Aust 2001; 174: 565-568.
- PBS expenditure and prescriptions. January 2000 to December 2000. Canberra: Commonwealth Department of Health and Aged Care, 2001. Available at <http://www.health.gov.au/internet/wcms/publishing.nsf/Content/health-pbs-general-pubs-pbbexp-pbdec00-index.htm>.