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.

Fatal neurogenic pulmonary edema in a patient with progressive multiple sclerosis

We report a case of fatal neurogenic pulmonary edema in progressive multiple sclerosis (MS). The patient had one isolated relapse-like episode. Six years later progressive disease began, lasting 5 years until unexpected death during sleep. Medico-legal autopsy revealed pulmonary edema and neuropathological examination showed infiltrations with lymphocytes and microglia in the respiratory centers of the medulla. More classical demyelinated lesions were found in the white matter of spinal cord and in the gray matter of the brain along with disseminated perivascular lymphocytic infiltrates. Medullary inflammation in progressive MS may result in sudden fatal respiratory failure.

Cholestasis and regulation of genes related to drug metabolism and biliary transport in rat liver following treatment with cyclosporine A and sirolimus (Rapamycin)

Cyclosporine A and sirolimus are used alone or in combination as immunosuppressants in organ transplantation. To elucidate hepatic side effects, we examined hepatic mRNA of proteins involved in biliary and hepatocellular transport of drugs, formation of glutathione (GSH) and drug metabolising cytochrome P-450 enzymes (CYPs) in rats treated orally for 2 weeks with cyclosporine A (15 mg/kg/day), sirolimus (0.4 mg/kg/day), their combination (same doses), or vehicle. Liver function tests (alanine aminotransferase, alkaline phosphatase, gamma-glutamyl transferase and bilirubin) in blood were then analysed as were hepatic mRNA levels of canalicular transport proteins (Mrp2, Bsep, Mdr1b and Mdr2), sinusoidal transport proteins (Ntcp, Oatp1 and Oatp2), GSH related enzymes (gamma-glutamylcysteine synthetase light (GCSlc) and heavy (GCShc) chain subunits and glutathione-S-transferase) and CYPs (CYP3A9, CYP1A2, CYP2E1 and CYP2BI/II). Cyclosporine A caused moderate cholestatic changes in liver enzymes, which was synergistically exacerbated by sirolimus. The data suggest that the underlying mechanisms behind cholestasis were not totally identical in the different treatment regimens. Cholestasis secondary to cyclosporine A could be related to reduction in mRNA expression of GSH synthesising enzymes and Mrp2, leading to reduced protection against oxidative stress and reduced bile acid-independent bile flow. After sirolimus treatment, Mrp2 mRNA was also reduced together with reduced levels of most CYPs and increased Oatp2, possibly leading to accumulation of toxic metabolites in the hepatocytes. The enhanced cholestatic effect of the combination treatment could be related to reduced GSH synthesising enzymes and even more pronounced reduction in Mrp2 mRNA and increase of Oatp2 mRNA.