Blinded Versus Unblinded Evaluations of Motor Scores in Patients with Parkinson's Disease Randomized to Deep Brain Stimulation or Best Medical Therapy

In deep brain stimulation (DBS) trials, blinded evaluation of patients using established disease-specific scales is considered gold standard for objective evaluation of results. Incidentally, an Editorial recently published in the BMJ stated that “re-evaluation of the role of blinding may be especially welcome in surgery, where it presents a particular challenge”. In an observer-blinded trial of DBS in the caudal Zona Incerta versus best medical management, we aimed at evaluating possible differences between blinded and unblinded scores of the motor part of the Unified Parkinson’s Disease Rating Scale (UPDRSIII). Seventeen patients with Parkinson’s disease (four women, age 58 10 years, disease duration 9.6 5.3 years) were scored after overnight medication withdrawal (off-med scoring) then again 1 hour after administration of a L-dopa dose 50% higher than the patient’s normal morning dose (on-med scoring), and randomized to either DBS (eight patients) or best medical management (nine patients). At the 6 months follow up, the nine patients in the medical arm were scored again exactly as at baseline. The eight patients who had received DBS were scored in four conditions: off-medication on stimulation (off-med on-stim), offmedication off-stimulation (off-med off-stim), on-medication off-stimulation (on-med off-stim), and on-medication onstimulation (on-med on-stim). The scorings were administered by an unblinded specialist nurse with 15 years experience of scoring UPDRS. The patients had a surgical cap covering the head during each scoring, and all scorings were videotaped. The videotapes were presented in random order and without audio to two clinicians specialists in movement disorders (one neurologist and one neurosurgeon, with more than 30 years experience in the field) who were not involved in the selection of patients, or surgery, or follow up. When scoring UPDRSIII on videotapes, neither speech nor rigidity (items 18 and 22 of UPDRSIII) could be evaluated. Therefore, when comparing the blinded sum scores with unblinded ones, the values of these two items were excluded from the DBS nurse’s sum scores. In case of discrepancies of scores between the two blinded clinicians, the videotape was viewed again and a consensus score was reached between them. Statistical analysis of the results was performed with SPSS. The Shapiro–Wilk test was used to test for normality. The Wilcoxon sign-rank test was used and results expressed in Median and InterQuartile range. Z-value was calculated. The level of significance was set to P < 0.05. In total, 84 unblinded and 84 blinded UPDRSIII scorings were performed. Table 1 shows the scores according to the various medical and stimulation conditions: blinded vs. unblinded scores for patients undergoing L-dopa challenge showed no statistical difference, neither in off-med nor in on-med conditions. For patients who had DBS, there was a significant difference between scores only in off-med on-stim (P = 0.026) and in onmed on-stim (P = 0.011) conditions. Here, the median UPDRSIII scores rated by the unblinded nurse were 2.5 points lower than those rated by the blinded clinicians. Our study showed a good agreement between the DBS nurse’s unblinded scores and those of the blinded clinicians. The only significant differences concerned two conditions: off-med onstim and on-med on-stim. Here the difference of the median values of UPDRSIII between evaluators amounted to only 2.5 points with almost similar interquartile range. Unsurprisingly, the