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Imai et al. examined the association between the dosing regimen of oral prednisolone (PSL) and the achievement of minimal manifestation status or better on PSL <=5 mg/day lasting >6 months in patients with generalized myasthenia gravis (1). The authors classified 590 patients into high-dose, intermediate-dose and low-dose (n=166) groups, and logistic regression analysis was applied to know the prognosis of patients in low-dose group, by splitting observational period into 1 to 3 years of treatment. The authors concluded that a low-dose PSL regimen with early combination of other treatment options was significantly associated with good prognosis. I have two concerns about their study.
First, the dosing regimen of oral PSL should be considered with caution. Namely, the authors set the maximum dose of oral PSL in each group, and standard treatment schedule was selected after each patient was allocated. Mean daily dose of PSL does not become highest in high-dose group in the study, which happens in the study protocol. In addition, there is a possibility of higher frequency in patients with combination of other treatment options, when patients were registered into low-dose group. As the age of onset was higher and disease duration was shorter in patients with low-dose group, randomized allocation should be strictly conducted in further study.
Second, the number of events was not enough after 1 year observation, and higher odds ratios with wide ranges of con...
Second, the number of events was not enough after 1 year observation, and higher odds ratios with wide ranges of confidence interval were observed. As the follow-up period become longer, odds ratios become small, although significance disappeared in comparison between low-dose and high-dose groups after 3 year observation. I suppose that confounders for the prognosis were not completely adjusted, and there is a limitation of study design in multicentre cross-sectional study.
1. Imai T, Utsugisawa K, Murai H, et al. Oral corticosteroid dosing regimen and long-term prognosis in generalised myasthenia gravis: a multicentre cross-sectional study in Japan. J Neurol Neurosurg Psychiatry 2017 Nov 24. doi: 10.1136/jnnp-2017-316625