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Editors Selection IGR 8-3

Health economics: Cost of SLT and medical treatment

Comment by Mireia Jofre on:

13995 Projected cost comparison of selective laser trabeculoplasty versus glaucoma medication in the Ontario Health Insurance Plan, Lee R; Hutnik CM, Canadian Journal of Ophthalmology, 2006; 41: 449-456

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The purpose of this study by Lee and Hutnik (957) is to analyze whether there are cumulative cost-savings of using Selective Laser Therapy (SLT) over using medication to treat glaucoma.

To do so, the authors review 707 patient charts selected randomly from five ophthalmologic practices across Ontario, and use these data to calculate the cost of Glaucoma medical therapy for three categories: Costs of patients on mono-therapy or on just one type of drugs; Costs of those on bi-drug therapy (two types of drugs); and, Costs of those on tri-drug therapy (three drugs). They estimate the cost of SLT under two scenarios: Repeat SLT is needed after two years of the initial one and repeat SLT is needed after three years instead. Then, they calculate and compare the cumulative costs of SLT and of glaucoma medication over six years.

There are cost savings of using SLT versus medication

The results they obtain are the following: There are cost savings of using SLT versus medication. The savings are more extreme in the case of the second SLT scenario where repeat SLT is needed only after three years. The magnitude of the savings of SLT versus medication is moderate. In the case of the two-year SLT repeat scenario the savings are of about $206 if compared to mono-therapy, $1668 if compared to bi-drug therapy and $2992 if compared to tri-drug therapy. In the case of the three-year SLT repeat scenario the corresponding figures are $580, $2042 and $3366.

The paper is neatly written and the idea interesting. Nevertheless, I have several caveats:

Major:

1. There is no analysis of how significant the reported differences in costs are. Standard deviations are not even reported. This is aggravated by the fact that the costs of those who failed SLT or medical therapy was not taken into account. Ex-ante it is difficult to know for which patients SLT (or medical therapy) will work. By using only the selected sample of those for which the therapy works, we are left with the doubt of what is the real cost estimate when the therapy is used as a first line treatment in general.

2. The extrapolation of costs from one year to six years is problematic. Costs of glaucoma patients do change over time and this kind of simplification is extreme. Although it does not go against the conclusions as if anything accounting for that would have inflated the medication costs, it is unnecessarily simplifying.

Minor:

1. The decision of leaving out the costs of side-effects and complications is somewhat problematic. Again, including those would not have hurt the main conclusion as it would have increased medical drops' costs most likely. Nevertheless we are left with the doubt of what is the corresponding magnitudes of the side of effects of both lines of therapy, medical and SLT. This information is needed when the purpose of the study is to compare the costs of both therapies.

2. The reviewer is uncertain as of what the authors mean in the last paragraph of page 451 when they explain that the cost difference was analyzed in the year preceding the year in which another episodic cost of SLT would be incurred.

In sum, this paper poses and interesting question and it provides a neat first attempt to answer it, but methodology used is weak and could have been strengthened by a better study design and statistical analysis.

(See also Introduction)

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