Impact of methodological choices in comparative effectiveness studies: application in natalizumab versus fingolimod comparison among patients with multiple sclerosis

Background

Natalizumab and fingolimod are used as high-efficacy treatments in relapsing–remitting multiple sclerosis. Several observational studies comparing these two drugs have shown variable results, using different methods to control treatment indication bias and manage censoring. The objective of this empirical study was to elucidate the impact of methods of causal inference on the results of comparative effectiveness studies.

Methods

Data from three observational multiple sclerosis registries (MSBase, the Danish MS Registry and French OFSEP registry) were combined. Four clinical outcomes were studied. Propensity scores were used to match or weigh the compared groups, allowing for estimating average treatment effect for treated or average treatment effect for the entire population. Analyses were conducted both in intention-to-treat and per-protocol frameworks. The impact of the positivity assumption was also assessed.

Results

Overall, 5,148 relapsing–remitting multiple sclerosis patients were included. In this well-powered sample, the 95% confidence intervals of the estimates overlapped widely. Propensity scores weighting and propensity scores matching procedures led to consistent results. Some differences were observed between average treatment effect for the entire population and average treatment effect for treated estimates. Intention-to-treat analyses were more conservative than per-protocol analyses. The most pronounced irregularities in outcomes and propensity scores were introduced by violation of the positivity assumption.

Conclusions

This applied study elucidates the influence of methodological decisions on the results of comparative effectiveness studies of treatments for multiple sclerosis. According to our results, there are no material differences between conclusions obtained with propensity scores matching or propensity scores weighting given that a study is sufficiently powered, models are correctly specified and positivity assumption is fulfilled.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12874-022-01623-8.

Value of TENS for relief of chronic low back pain with or without radicular pain

OBJECTIVES

To evaluate the efficacy of transcutaneous electrical neurostimulation (TENS) in patients with chronic low back pain (LBP).

METHODS

DESIGN

Prospective, randomized, multicentre, single-blind study.

SETTING

Twenty-one French pain centres.

PARTICIPANTS

Two hundred thirty-six consecutive adult patients consulting for chronic LBP, with or without radicular pain (mean age ± standard deviation: 53 ± 13 years; range: 28-86 years).

INTERVENTION

Patients were randomly assigned to receive either active (n = 117) or sham (n = 119) TENS in four 1-h daily treatment sessions for 3 months.

MAIN OUTCOME MEASURES

The primary outcome measured was improvement of functional status at 6 weeks (Roland-Morris Disability Questionnaire). Secondary outcome measures were improvement of functional status at 3 months, pain relief (weekly visual analogue scale assessments), positive functional repercussions of pain levels on quality of life, a diminution of the use of analgesic and anti-inflammatory medication, satisfaction with the overall treatment strategy and compliance.

RESULTS

Functional status did not differ between the groups, whether at 6 weeks or 3 months (p = 0.351 at 6 weeks). A significant improvement between the first and last visual analogue scale assessments was observed in patients with either lumbar pain alone or lumbar and radicular pain treated with active TENS. Other outcome measures did not differ significantly between the two groups.

CONCLUSION

There was no functional benefit of TENS in the treatment of patients with chronic LBP.

[Extrapontine myelinolysis of favorable outcome in a patient with autoimmune polyglandular syndrome]

INTRODUCTION

Extrapontine myelinolysis is a well-known complication of hyponatremia and its treatment. It rarely occurs without central pontine myelinolysis, usually after overly rapid correction of hyponatremia. Its prognosis is considered poor.

EXEGESIS

We report the case of a patient with autoimmune polyglandular syndrome with subacute adrenal failure responsible of severe hyponatremia. Despite a well-conducted treatment, the patient developed acute anxiety, catatonia, dysphagia and parkinsonism revealing extrapontine myelinolysis demonstrated on MRI. Outcome was favorable.

CONCLUSION

Extrapontine myelinolysis may occur in the absence of central pontine myelinolysis despite a treatment of hyponatremia conducted according to published guidelines. Treatment should be extremely cautious when hyponatremia has been lasting for more than 48 hours.

Devic disease and thymoma with anti-central nervous system and antithymus antibodies

A patient with myasthenia gravis and thymoma developed neuromyelitis optica (NMO) and necrotizing myositis 4 months after treatment of the tumor. Antibodies reacting with the CNS and thymic epithelial cells were detected in the serum during the acute phase of NMO, suggesting that the NMO was linked to the thymoma.

Paraneoplastic anti-CV2 antibodies react with peripheral nerve and are associated with a mixed axonal and demyelinating peripheral neuropathy

Subacute sensory neuronopathy with anti-Hu antibodies is the best-characterized paraneoplastic peripheral neuropathy associated with carcinoma. Anti-CV2 antibodies, another group of paraneoplastic antibodies, react with a 66-kd brain protein belonging to the family of Ulip/CRMP proteins. The manifestations associated with anti-CV2 antibodies include cerebellar degeneration, uveitis, and peripheral neuropathy. Some of these patients also have anti-Hu antibodies. We have compared the clinical, electrophysiological, and pathological characteristics of the peripheral neuropathy in 9 patients with anti-CV2 antibodies (3 of whom also had anti-Hu antibodies) and 12 patients with only anti-Hu antibodies. Data for patients with anti-Hu antibodies alone indicated subacute sensory neuronopathy. Patients with anti-CV2 antibodies had a mixed axonal and demyelinating sensory motor neuropathy that was sometimes superimposed on subacute sensory neuronopathy when both anti-CV2 and anti-Hu antibodies were present. Unlike anti-Hu antibodies, anti-CV2 antibodies reacted with peripheral nerve antigens, as shown by their ability to bind to a 66-kd protein in human and rat nerve on Western blot analysis and to immunolabel peripheral nerve axons and sensory neurons on immunohistochemical study.

[18F]fluorodeoxyglucose positron emission tomography in the diagnosis of cancer in patients with paraneoplastic neurological syndrome and anti-Hu antibodies

The diagnosis of cancer is often difficult in patients with paraneoplastic neurological syndrome and anti-Hu antibodies. Fluorodeoxyglucose 18 positron emission tomography scanning is a highly sensitive and specific method to detect lung tumors. We investigated 15 patients with paraneoplastic neurological syndrome and anti-Hu antibodies. Radiological methods led to the diagnosis of cancer in 12 patients, and test results were negative in 3. Whole-body [18F]fluorodeoxyglucose positron emission tomography showed abnormal uptake in the mediastinum in these 3 patients in accordance with the expected location of the malignancy.