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The effect of study design and analysis methods on recovery rates in Bell's palsy

Authors


  • This work was funded by Uppsala University; GlaxoSmithKline, Sweden; Pfizer AB, Sweden; Acta Otolaryngologica Foundation; Rosa and Emanuel Nachmansson's Foundation; Stig and Ragna Gorthon Foundation; Torsten Birger Segerfalk Foundation; Margit Arstrup's Foundation; the County Council of Skåne; and Helsinki University Central Hospital Research Funds. Mats Engström, MD was paid by GlaxoSmithKline for a lecture on Bell's palsy in 2001. The other authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Abstract

Objectives/Hypothesis:

We investigated how study design affects the rate of recovery in Bell's palsy.

Study Design:

Prospective, randomized, double-blind, placebo-controlled, multicenter trial.

Methods:

Data were extracted from the Scandinavian Bell's palsy study, which included 829 patients. The study design was factorial; 416 patients given prednisolone, 413 not given prednisolone, 413 patients given valacyclovir, 416 not given valacyclovir. Data were analyzed with intention-to-treat principle and complete-case analysis methods and recovery was defined as Sunnybrook score 100, House-Brackmann grade I or ≤grade II at 12 months.

Results:

With the intention-to-treat principle and last-observation-carried-forward method (n = 829) and recovery defined as Sunnybrook 100, 300 of the 416 patients (72%) receiving prednisolone had recovered compared with 237 of the 413 (57%) who did not receive prednisolone (P < .0001). With recovery defined as House-Brackmann grade I, the corresponding recovery rates were 324 of 416 (78%) and 266 of 413 (64%) (P < .0001). With complete-case analysis and recovery defined House-Brackmann grade I (n = 782), 335 of 389 patients (86%) given prednisolone recovered compared with 277 of 393 (70%) in the group not given prednisolone (P < .0001). With recovery defined as House-Brackmann ≤grade II (n = 797), the corresponding recovery rates were 380 of 396 (96%) and 353 of 401 (88%) (P < .0001). The analysis method affected the recovery rates in the valacyclovir and no-valacyclovir groups in a similar way as in the prednisolone and no-prednisolone groups.

Conclusions:

Recovery rates in a Bell's palsy study are substantially affected by the choice of analysis method and definition of recovery. Laryngoscope, 2009

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