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Purpose: To investigate the sensitivity and specificity of a newly developed diagnostic tool, the Amer Dizziness Diagnostic Scale (ADDS), to evaluate and differentially diagnose vestibular disorders and to identify the strengths and weaknesses of the scale and its usefulness in clinical practice.

Subjects and Methods: Two hundred subjects of both genders (Male72, Females 128) aged between 18 to 60 (49.5 ± 7.8) who had a history of vertigo and/or dizziness symptoms for the previous two weeks or less were recruited for the study. All subjects were referred from otolaryngologists, neurologists and family physicians in and around Jeddah, Kingdom of Saudi Arabia. On the first clinic visit, all the patients were evaluated once with the ADDS, following which they underwent the routine testing of clinical signs and symptoms, audiometry, and a neurological examination, coupled with tests of Vestibulo-Ocular Reflex function, which often serve as the "gold standard" for determining the probability of a vestibular deficit.

Results: The results showed that the ADDS strongly correlated with "true-positive" and "true-negative" responses for determining the probability of a vestibular disorder (r =0.95). A stepwise linear regression was conducted and the results indicated that the ADDS was a significant predictor of "true-positive" and "true-negative" responses in vestibular disorders (R2 =0.90). Approximately 90% of the variability in the vestibular gold standard test was explained by its relationship to the ADDS. Moreover, the ADDS was found to have a sensitivity of 96% and specificity of 96%.

Conclusion: The study showed that the Amer Dizziness Diagnostic Scale has high sensitivity and specificity and that it can be used as a method for differential diagnosis of patients with vestibular disorders.

Dizziness; Diagnostic; Scale

Dizziness is one of the most common complaints in medicine and describes various abnormal sensations relating to perceptions of the body’s relationship to space. The prevalence of dizziness in the general population ranges from 20% to 30% [1]. Typically, dizziness is divided into four subtypes: vertigo, lightheadedness, disequilibrium and oscillopsia, and this classification is still the basic definition of dizziness [2,3]. In many patients dizziness causes serious functional impairments [4]). An important problem in clinical decision-making regarding patients with vestibular disorders is the trial-and-error method of diagnostic procedures, which consumes a lot of time and money for both clinicians and patients. Since the causes of vestibular disorders are multi-factorial, reaching a correct diagnosis can be quite challenging for clinicians [5-8]. Currently, with the evolution of high-tech advances, a wide range of laboratory tests are available for evaluation of the vestibular and balance systems alongside clinical history; these include: video nystagmography (VNG) recording for eye examinations, caloric test and rotary chair testing, Vestibular Evoked Myogenic Potential (VEMP), Subjective Visual Vertical and Computerized Dynamic Posturography and electro nystagmography (ENG) [9-11]. Traditionally, electronystagmography which relies on the corneo-retinal potential to record the eye movements, has been considered the ‘gold standard’ for testing dizzy patients. Video nystagmography is a recent introduction which offers a multitude of advantages over traditional electronystagmography protocols. In contrast to electronystagmography, video nystagmography records the eye movements using digital video image technology, utilizing infrared illumination to determine eye position. The use of video nystagmography enables simultaneous subjective observation of eye movements together with objective collection and analysis of eye movement waveforms via computer algorithms [12]. Since dizziness is a highly subjective matter [13], the single most important element in reaching a correct diagnosis in dizziness patients is obtaining an accurate history. The Vertigo Symptom Scale (VSS) by Yardley et al is a disease-specific subjective questionnaire to quantify balance disorders, somatic anxiety, and autonomic severity symptoms [14]. The VSS consists of two subscales: the Vertigo scale (VSS-VER), which assesses symptoms mainly associated with disorders of the vestibular system, and the Anxiety and Autonomic symptom scale (VSS-AA) for the assessment of a group of generic symptoms which may be associated with autonomic arousal or somatic expressions of anxiety [15,16]. Also, in 1990, Jacobson and Newman designed and validated a specific questionnaire for dizziness, the Dizziness Handicap Inventory (DHI), which evaluated the self-perception of the incapacitating effects on quality of life caused by dizziness. The DHI is a useful tool for physiotherapists and professional rehabilitation teams, enabling them to list patients’ problems, define intervention goals, and plan and evaluate treatment and/or rehabilitation programs [17]. Even though both these scales are used in dizziness patients, they are primarily used for those who have been already diagnosed, to establish the intensity of dizziness and the functional impact of dizziness in life. But before using any of these tests and scales, it is always preferable to provide direction for the clinician as to how to proceed with further assessment and examination of a patient who presents with a complaint of dizziness so that unnecessary diagnostic procedures can be avoided.

The wide variation in patient symptoms and the lack of knowledge about the natural history of some vestibular impairments complicate the selection of patients who might be good candidates for vestibular rehabilitation. There is thus a need for sensitive and specific methods for identifying patients with vestibular impairment so as to enable the clinician or the rehabilitation member to direct them to the right treatment. For diagnosing peripheral vestibular dysfunction, the first step in the procedure is the patients' report of symptoms, which can infer the presence of a vestibular deficit. If the questions are not described properly, the outcome of the diagnosis may vary. For this reason, there is frequently a lack of association between symptoms and the actual detection of vestibular abnormalities [18]. The vestibular tests, however, do not characterize the vestibular deficit in terms of the patient's functional deficit, and thus have limited value for identifying balance deficits related to vestibular dysfunction [19]. The most commonly diagnosed vestibular disorders include benign paroxysmal positional vertigo (BPPV), labyrinthitis or vestibular neuritis, Ménière’s disease, secondary endolymphatic hydrops, and perilymph fistula. Vestibular disorders also include superior canal dehiscence, acoustic neuroma, ototoxicity, enlarged vestibular aqueduct, and mal de débarquement. Other problems related to vestibular dysfunction include migraine associated vertigo and complications from autoimmune disorders and allergies.

Subjects

Procedure

Two hundred subjects (n=200) participated in this study. The demographic and baseline clinical characteristics of patients with Vestibular Disorders who were recruited in this study are presented in Table 1. Results showed that the ADDS strongly correlated with the "true-positive" and "true-negative" results (r=0.95, p<0.05). A stepwise linear regression was conducted and the results indicated that ADDS was a significant predictor of "true-positive" and "true-negative" results (R2=0.90, p<0.05). Approximately ninety percent of the variability in "true-positive" and "true-negative" results was explained by its relationship to the ADDS.

Moreover, the Amer Dizziness Diagnostic Scale has been found to have a sensitivity of 96% and specificity of 96% that can adequately capture a possible diagnosis of people with vestibular disorders, (Table 2). In this study, the coefficient (r) range for validity for ADDS was acceptable, at 0.766. Furthermore, content validity has been obtained through examination by a bilingual panel (Arabic and English) of 12 experts, recruited to establish the content validity of the ADDS instruments. The panel consisted of experts in the fields of, otolaryngology, vestibular therapy. However, panel experts summarized the criteria for content validity, as used in this paper for ADDS are: clear and simple wording of questions, easy to understand, relevant to purpose of the expected diagnosis, comprehensive questions, appropriate language, appropriate length for each question, no bias in responses in either direction.

The purpose of the current study was to evaluate the sensitivity and specificity of a newly developed diagnostic scale, the Amer Dizziness Diagnostic Scale (ADDS), to evaluate and differentially diagnose vestibular disorders and adequately capture possible disorders in people with vestibular dysfunctions and to identify the strengths and weaknesses of its usefulness in clinical practice. It also aimed to understand the feasibility of the ADDS as a first-line evaluation tool in general clinics so that even those who are not specialized in these areas can effectively screen a patient who complains of dizziness and can refer him or her to the appropriate specialty for further diagnosis and management, since the cause for the dizziness is multi-factorial. Dizziness is one of the most common complaints in medicine and describes various abnormal sensations relating to perception of the body’s relationship to space. Typically, dizziness is divided into four subtypes – vertigo, lightheadedness, disequilibrium and oscillopsia – and this classification is still the basic definition of dizziness [2,3]. Since dizziness is highly subjective [13], the components of the ADDS basically focus on subjective questions with which ultimately we can detect a diagnosis, and ADDS is a clinical tool that classifies the reasons for dizziness. To our knowledge, this is the first study to develop a comprehensive scale to differentially diagnose patients complaining of dizziness, which is updated and extended to take account of key developments in research and practice in dizziness as a first-line evaluation tool. While there are many scales used in dizziness patients, such as the DHI and the VSS-VER [12,13], these scales are all basically used for patients who have already been diagnosed, to establish the intensity of dizziness and its functional impact. But before using any of these tests and scales, it is always preferable to provide direction for the clinician as to how to proceed with further assessment and examination of a patient who presents with dizziness so that the unnecessary diagnostic procedures can be avoided. We consider this study as fundamental for evaluating and treating dizziness patients appropriately. All healthcare workers will find the ADDS to be a relevant tool as well as a reliable reference guide that promotes best practice care for the differential diagnosis, evaluation and treatment of dizziness. The single most important element in reaching a correct diagnosis in dizziness patients is obtaining an accurate history. However, in the absence of a valid diagnostic scale for dizziness, the clinician is put in a difficult situation where they may not able to differentially diagnose patients. The results of this study indicate that the ADDS has high sensitivity and specificity and can be used as a method for differential diagnosis of patients with vestibular disorders. Therefore, the ADDS provides clinicians with an objective measure to help in clinical decision-making process and can be used as a first-line evaluation tool in general clinics so that even those who are not specialized in these areas can effectively screen patients who complain of dizziness and can refer them to the appropriate specialty for further diagnosis and management.

The next step in the validation of the ADDS will be to demonstrate that it has comparable reliability and validity across a range of languages and cultural settings. Translation and validation in several languages for the final version of the ADDS will include translation instructions and a list of languages that will help a variety of patients from different countries and cultural contexts in order to select additional cross-culturally relevant items to assess more demanding and social activities and to establish the reliability and discriminant validity of the ADDS. A major advantage of establishing a scale suitable for use in a wide range of contexts is that this will permit direct comparison between studies and populations in different countries and settings. This study suggests that the ADDS is an ideal tool for this role, as it has close continuity with the best existing measure of Vestibular Disorders. The ADDS includes seventeen questions which are divided into five categories; the first seven questions are general information questions that are intended for statistical and future research purposes [20]. The next three questions are specific to UVH and totally represent the features of UVH patients, especially drifting towards the same side while walking, which is a classical finding in UVH [21]. The third set of questions are focused on the diagnosis of BPPV, where all these patients experiences the features of dizziness while moving the head and with different body movements [3,4]. The fourth group of questions are related to Centrally Mediated Problems and the importance of these questions is to understand the role of different clinical specialties, as UVH and BPPV can be treated by a physical therapist, whereas if a centrally mediated problem is diagnosed, a referral and consultation with a neurologist, neuro-physiologist, neuro psychiatrist or neurosurgeon is required. Thereby each team member in the clinical rehabilitation can limit themselves in the diagnosis and management of patients with various neurological symptoms, which will ultimately benefit both the clinician and the patient [22]. The last question, which is about dizziness episodes, relates to all previous vestibular disorders, in addition to Cervicogenic Dizziness (CGD), and the diagnosis of CGD comes as a diagnosis of exclusion if all other possible causes are ruled out. This scale is of benefit for both clinicians and patients because it avoids unwanted and expensive diagnostic procedures and saves considerable time.

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