Causal inference methods to study gastric tube use in amyotrophic lateral sclerosis.

OBJECTIVE

To estimate effects of gastric tube (G-tube) on survival and quality of life (QOL) in people with amyotrophic lateral sclerosis (ALS) correcting for confounding by indication inherent in nonrandomized observational data.

METHODS

To complement a recent causal inference analysis, which concluded that G-tube placement increases the hazard of death, permanent assisted ventilation, or tracheostomy by 28%, we fit causal inference models on a different sample of 481 patients with ALS enrolled in a recent clinical trial of ceftriaxone. Forward selection identified predictors of G-tube placement. Effects of G-tube on survival and QOL were estimated using structural nested models and marginal structural models, accounting for predictors of G-tube treatment.

RESULTS

Forced vital capacity and the total score and bulbar subscale of the revised ALS Functional Rating Scale best predicted G-tube placement. Correcting for these confounders, G-tube placement decreased survival time by 46% ( < 0.001) and had no effect on QOL ( = 0.078). Sensitivity survival analyses varied in significance, but none revealed a survival benefit.

CONCLUSIONS

In the absence of randomization, causal inference methods are necessary to correct for time-varying confounding. G-tube placement may have a negative effect on survival with no QOL-related benefit for people with ALS. A randomized controlled trial is warranted to further evaluate the efficacy of this widely used intervention.

CLINICALTRIALSGOV IDENTIFIER

NCT00349622.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that for patients with ALS, G-tube placement decreases survival time and does not affect QOL.