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Correction
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Bartalena et al.,
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We think the authors should have carried out an intention-to-treat analysis of the results at one year in all patients in each group. Instead, in Table 3, the data in subgroups of patients who had no change, worsening, or improvement are shown separately. Comparisons are then made within these selected subgroups. This approach violates a basic premise of the analysis of data in randomized trials. Was this done because there were no statistically significant differences between the treatment groups when the results in all patients in each treatment group were compared?
Ophthalmopathy may develop before, concurrently with, or after the diagnosis of hyperthyroidism.2 New cases of ophthalmopathy cannot be attributed to radioiodine therapy. The number of such cases that would have developed had the patients remained untreated is unknown. Other studies have reported improvement in ophthalmopathy in radioiodine-treated patients.2
In Table 3, the mean (±SD) pretreatment and post-treatment scores for ophthalmopathy activity for the patients in the radioiodine–prednisone group who had improvement were both 2±1, but the P value for the comparison was given as <0.001. How can this be?
Colum A. Gorman, M.B., B.Ch., Ph.D.
Kenneth P. Offord, M.Sc.
Mayo Clinic
Rochester, MN 55905
References
To the Editor: The main end point of our study was the change in the course of ophthalmopathy, expressed as progression or improvement of eye disease after treatment of hyperthyroidism. The categories of no change, worsening, and improvement were defined by using an overall evaluation of ocular changes. In our opinion, the outcome of ophthalmopathy is better assessed by combining multiple criteria than by evaluating each single criterion separately, because variations in a single criterion are not necessarily representative of the overall ocular changes. On the basis of these premises, the analysis of data from the 443 patients, reported in the paper and shown in Figure 1 and Figure 2, revealed clear differences in the three groups. Table 3 was mainly descriptive, with the aim of showing the degree of change in individual criteria in each subgroup, and was not the basis for the overall evaluation of the course of ophthalmopathy.
As for the other point raised by Drs. Gorman and Offord, we agree that Graves' ophthalmopathy may occur before, concomitantly with, or after the diagnosis of hyperthyroidism. However, a relation between radioiodine therapy and the course of ophthalmopathy is supported, in our view, by the following considerations: the higher number of patients with progression of ophthalmopathy in the radioiodine group (23, 6 of whom had newly developed eye disease, as compared with 4, 1 of whom had newly developed eye disease, in the methimazole group); the time course of the progression of ophthalmopathy, which occurred shortly after radioiodine therapy; and the often transient progression of ophthalmopathy after radioiodine administration. Admittedly, we did not include a control group of patients with hyperthyroidism that was left untreated, but it would be unethical not to treat such patients for a year.
Drs. Gorman and Offord are right about the pretreatment and post-treatment activity scores in the radioiodine–prednisone group. The actual figures in the original version were 2.2±0.6 before treatment and 0.9±0.5 after treatment. The values were subsequently rounded, and because of a typing error, the post-treatment value was given as 2±1 instead of 1±1; the difference between this value and the pretreatment value is statistically significant, as indicated in Table 3. We apologize for this mistake.
Luigi Bartalena, M.D.
Claudio Marcocci, M.D.
Aldo Pinchera, M.D.
Università degli Studi di Pisa
56124 Pisa, Italy
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