Supplemental Data:
Survey information
The survey was conducted from September 16, 2013 to February 2 nd, 2014. The
study was designed by neurologists, a psychologist and a physicist who developed a
videooculography device to perform quantitative HIT. All of the developers have
longstanding experience in examining patients with vertigo and dizziness (vertigo
outpatient centers). Pilot testing was performed for 3 months before distribution
engaging several experienced and naive neurologists (neurological departments,
practitioner). It contained 14 questions with either single or multiple-choice answer
format; see original survey on supplemental data. Question #2 required multiple
answers in %. Forward was not possible unless the sum added up to 100%. The
average duration participants took to answer the survey was 336±197 sec (median
286 sec), i.e. about 4.7 minutes. The link to the survey was posted on the homepage
of the German Neurological Society (DGN) and the survey was also announced in
official quarterly email letters of the DGN to their members. The survey was not
sponsored by any company. There were no financial incentives to participation or
non-material benefits offered. Anonymity was guaranteed since participants were not
asked for names or personal data allowing any identification. Repetitive participation
was largely excluded by setting a cookie on the computer used. Response to each
question was mandatory to proceed. The demographics and clinical training history
obtained on participants is given in the text. More than 50% of respondents indicated
that from all their everyday patients less than 25% present with vertigo; in 42% of
respondents 26-50% present with vertigo.
The survey was developed using LimeSurvey (www.limesurvey.org, version 2.00+,
build 130802), an open-source tool (GNU, general public license), running on a
server in the Department of Neurology, Luebeck.
Statistics
Statistical calculations were performed using SPSS (IBM SPSS Inc., Armonk, NY;
version 22.0.0.1). The examinations to differentiate peripheral vestibular from central
cause (Fig. 1A) differed between specialists and residents in the categories “medical
history” (Mann-Whitney U-Test, z = 3.2, p = 0.002), “normal cMRI” (z = -2.3, p =
0.023) and “normal cCT” (z = -3.5, p = 0.001).
The relative importance of specific ocular motor and other neurologic signs for
diagnosis differed significantly between the categories (Friedman-Test, Chi²=29.9,
df=3, p < 0.001, Fig. 1B). Post-hoc Wilcoxon tests showed significant differences
between “Head impulse test” and “no skew deviation” (z = -3.5, p < 0.001) as well as
“horizontal-torsional nystagmus” (z = -3.0, p = 0.003). Furthermore “No additional
neurologic signs” differed significantly to “horizontal-torsional nystagmus” (z=-4.0, p <
0.001) and “no skew deviation” (z = -4.3, p < 0.001).
Limitations of the study
The study design bears some inherent confounds. Five percent is an expected
and reasonable yet not representative number of participants in this kind of
internet based survey. Although the survey comprised a fairly large number of
neurologists it represents the diagnostic approach of only a minority of
neurologists in Germany. Participating neurologists were probably more
interested and experienced in dizziness than non-participants. Therefore the
high frequency of clinically applied HIT indicated by the respondents may not
be representative. The study can also not answer whether participants'
responses are based on clinical or theoretical grounds (e.g., published
literature, lectures at meetings, local subspecialist neuro-otology consultants
or practical experience with vertigo patients). There were no uncued or multiple
choice questions asked that might have assessed the knowledge of those
individuals who stated they frequently relied on bedside skills. Accordingly, it
remains unknown whether the specific skills are correctly and consistently
performed at the bedside (i.e., whether confidence matches competence), since
these two may be dissociated [1]. But this was not the primary goal of this
survey. We consider it likely that non-participants were less aware of the HIT
and that their self-confidence in taking patient's history and HIT is even much
smaller. Thus, even the participants interested in diagnosing vertigo lack selfconfidence in their own clinical skills.
1.
Friedman CP, Gatti GG, Franz TM, Murphy GC, Wolf FM, Heckerling PS, Fine PL, Miller
TM, Elstein AS (2005) Do physicians know when their diagnoses are correct?
Implications for decision support and error reduction. J Gen Intern Med 20:334-339