High rates of IVIG use found in myasthenia gravis review

Movement disorders

By Michael Woodhead

11 Dec 2019

High use of intravenous immunoglobulin (IVIG) in Australian patients with myasthenia gravis may be due to underuse of other steroid-sparing immunosuppressants (SSI), a Victorian study suggests.

A review of the management of 66 patients with MG at a Victorian neurology centre found that in most aspects their disease features and treatment were generally consistent with the literature.

But the review, conducted by Dr Vivian Li and colleagues at the Department of Neurology, Frankston Hospital, Melbourne Peninsula Health found that 60% of patients were receiving maintenance IVIG (40% first line use). This was higher than the rate of 30% expected from the national average and National Blood Authority estimates.

The investigators said there were several possible factors to explain the high use of a scarce and costly resource.

High IVIG use might be due to many patients (32%) having bulbar dysfunction, where IVIG is favoured due to quicker response, they suggested.

And IVIG may have been needed as rescue therapy for several patients who were started on high doses of predisolone (40mg or more), which may lead to initial deterioration.

They also found that other SSI were underused or underdosed in the patients at their centre. About one in five patients on maintenance IVIG had not been on SSI, some of whom may have been stabilised on it, they noted. In addition, the mean dose of 100 mg for azathioprine in the patients using it was lower than recommended.

In other respects, the patients presented and were managed as would be expected from literature. There was little apparent diagnostic delay, with the mean time from symptom onset to diagnosis being 3.34 months .

The commonest presenting symptoms were ocular (69.7%), bulbar ( 31.8%), limb (24.2%), facial/neck (19.7%) and respiratory(9, 13.6%). Of the 45 patients with known serology, 73% were AChR antibody-positive, two (4.44%) MuSK antibody-positive and 22%) seronegative.

The most widely used therapies were pyridostigmine (87.9%) and prednisolone (84.8%), followed by azathioprine (56%) and mycophenalate motelum (12%). Other SSI such as rituximab were not used due to access restrictions.

“Our study highlights the importance of reviewing therapies, including indications for and objective responses to treatment, to ensure use is rationalised and efficacious,” the authors concluded.

The findings are published in the Internal Medicine Journal.

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