Neck pain is one of the most prevalent musculoskeletal conditions worldwide, significantly impacting quality of life, functional ability, and productivity. It can result from various etiologies such as poor posture, cervical disc degeneration, trauma, or neurologic conditions like cervical radiculopathy. Given its multifactorial nature and its impact on daily functioning, a valid and reliable assessment tool is crucial to quantify the level of disability and monitor clinical outcomes.Neck pain represents a substantial public health problem worldwide and is among the leading causes of years lived with disability (YLDs). According to the Global Burden of Disease Study, neck pain affects more than 200 million people globally and its prevalence continues to increase due to population aging, sedentary lifestyles, and occupational risk factors (1). In Europe, musculoskeletal disorders including neck pain are among the most common causes of functional limitation and work absenteeism. Although epidemiological data specific to Albania are limited, regional estimates from Southeastern Europe suggest that the prevalence of neck pain ranges between 20 and 30% in the adult population, particularly among individuals engaged in sedentary occupations and prolonged computer use. The increasing burden of neck pain in this region highlights the need for reliable and culturally adapted patient-reported outcome measures to assess disability and monitor treatment outcomes (2). The Neck Disability Index (NDI), developed by Vernon and Mior in 1991, is one of the most widely used instruments for assessing selfreported disability in patients with neck pain (3). It consists of 10 items evaluating pain intensity and interference with activities of daily living such as personal care, lifting, reading, concentration, work, driving, sleeping, and recreation. Each item is scored from 0 to 5, with a total score ranging from 0 to 50, which is often converted to a percentage. Higher scores indicate greater disability. Since its development, the NDI has been extensively studied and recognized for its strong psychometric properties including internal consistency, testretest reliability, construct validity, and responsiveness (4,5).NDI has been translated and culturally adapted into numerous languages and validated across diverse populations worldwide. Previous validation studies have confirmed its applicability in European, Middle Eastern, Asian, and American populations, demonstrating its widespread clinical use in assessing neck-related disability. These cross-cultural adaptations have enabled clinicians and researchers to evaluate neck pain outcomes consistently across different healthcare systems and cultural contexts. The availability of validated translations of the NDI has therefore played a critical role in facilitating international research collaboration and improving comparability of clinical outcomes across studies (6).In addition to these adaptations, the NDI has also been validated in Brazilian Portuguese populations, demonstrating reliability ranging from reasonable to excellent and confirming adequate construct validity for assessing neck-related disability in clinical and research settings. This further illustrates the widespread international adoption of the NDI as a standardized instrument for evaluating functional limitations associated with neck pain across diverse cultural contexts (7).Given the multifactorial nature of neck pain and its impact on daily functioning, accurate assessment of disability requires instruments that capture both physical limitations and patient-perceived functional impairment. Patient-reported outcome measures (PROMs) have become an essential component of musculoskeletal assessment because they provide direct insight into the patient's perception of symptoms, activity limitations, and participation restrictions. Compared with clinician-based measures, PROMs are easy to administer, cost-effective, and feasible for use in both clinical practice and large-scale research settings. These instruments allow standardized evaluation of functional disability, facilitate monitoring of treatment outcomes, and support evidence-based decision-making in rehabilitation and musculoskeletal care. Consequently, PROMs such as the NDI have become widely adopted tools for evaluating neck-related disability in both clinical and research contexts (8).Despite the wide global adoption of NDI, no validated Albanian version exists to date. This presents a significant gap in clinical practice and research in Albanian-speaking populations. Health professionals in Albania and Kosovo often resort to foreign-language instruments, which may lead to misinterpretation and reduced accuracy in evaluating patient outcomes. The lack of culturally adapted tools compromises both individual care and population-level research.The process of cross-cultural adaptation and validation follows rigorous methodological guidelines, such as those proposed by the ISPOR Task Force (9). This includes forward and backward translation, expert committee review, pretesting with target populations, and statistical testing of psychometric properties such as internal consistency, test-retest reliability, and construct validity. The use of validated PROMs is crucial for evidence-based practice and ensures consistency in treatment planning and research (10).The primary aim of this study is to conduct the translation, crosscultural adaptation, and psychometric validation of the NDI for the first time in the Albanian language. By doing so, this study aims to provide clinicians and researchers with a reliable and validated tool to measure neck-related disability in Albanian-speaking patients. This is essential for improving patient assessment, ensuring standardized data collection, and facilitating international collaboration in musculoskeletal health research.A multicentric cross-sectional, observational, and methodological study was conducted to adapt and validate the NDI into the Albanian language. The study followed established guidelines for cross-cultural adaptation of self-report measures and for evaluating psychometric properties (11).The study included adult Albanian-speaking participants with a clinical diagnosis of neck pain, recruited online as per eCOA implementation user guide for Electronic Clinical Outcomes Assessment (eCOA) developers, solution designers/architects or individuals responsible for the electronic implementation of eCOAs, as well as Mapi Research Trust's eCOA Team which facilitated the permission to translate the Albanian NDI version. Prior to accessing the questionnaire, all participants were presented with a digital information sheet describing the purpose of the study, the voluntary nature of participation, confidentiality of responses, and the right to withdraw at any time without consequences. Participants were required to provide electronic informed consent by selecting an agreement option before proceeding to the questionnaire. Only individuals who confirmed their consent were allowed to continue and complete the survey. The study protocol was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki.Participants were eligible for inclusion if they were aged 18 years or older, were native Albanian speakers or had sufficient proficiency in the Albanian language to understand the questionnaire, reported experiencing neck pain at the time of participation, and provided electronic informed consent to participate in the study. Individuals were not included if they were younger than 18 years of age, were unable to understand the Albanian language, or declined to provide informed consent.Frontiers in Medicine 03 frontiersin.orgSeveral exclusion criteria were applied to ensure that the study population represented individuals with nonspecific neck pain and that participants were able to complete the questionnaire reliably. Participants were excluded if they reported a history of cervical spine surgery, diagnosed neurological disorders, malignancy affecting the spine, or previously diagnosed inflammatory rheumatic diseases involving the cervical spine, such as ankylosing spondylitis or rheumatoid arthritis with cervical involvement. These conditions were excluded to ensure that the questionnaire assessed disability related primarily to nonspecific or mechanical neck pain rather than secondary cervical pathology.To ensure that participants were able to understand and complete the questionnaire accurately, cognitive eligibility was assessed through self-reported screening questions included at the beginning of the online survey. Participants were asked whether they had any diagnosed neurological or cognitive condition that could interfere with the comprehension of written material. Individuals reporting cognitive impairment or severe neurological disorders were excluded from participation. Additionally, questionnaires that were incomplete or contained missing responses were excluded from the final analysis.The sample size was determined based on recommendations for validation studies (minimum of 5-10 participants per item), with a target of at least 100 participants to ensure robust statistical analysis (12).The study received ethical approval from the Albanian Health and Social Ministry Ethics Committee (Protocol ID: 208/9) and from the Ethics Committee of the Catholic University of Murcia (UCAM) (Approval ID: CE012516). It was prospectively registered at ClinicalTrials.gov under the identifier NCT06833359 (https:// clinicaltrials.gov/study/NCT06833359?cond=Albanian%20 Neck%20Disability%20Index&viewType=Card&rank=1). All methods were performed in accordance with the relevant guidelines and regulations. Written informed consent has been obtained from the patients. Research involving human research participants must have been performed in accordance with the Declaration of Helsinki.Neck Disability Index (NDI): A widely used self-report questionnaire assessing neck-specific disability across 10 items, each scored from 0 (no disability) to 5 (complete disability), for a total score ranging from 0 to 50. Higher scores indicate greater disability (13,14).Albanian version of the NDI (ANDI): The NDI was translated and culturally adapted into Albanian following internationally accepted procedures.The NDI was translated into Albanian using a standardized forward-backward translation method. Two bilingual translators independently translated the original English version into Albanian. A synthesis version was then back translated by two native English speakers blinded to the original.The pre-final Albanian version of the NDI was administered to a pilot group of 83 native Albanian speakers to evaluate clarity, comprehension, and cultural relevance of the translated items. Although cross-cultural adaptation guidelines typically recommend a minimum of 30 participants for pre-testing, a larger sample was intentionally included in this study to capture a broader range of demographic characteristics and to obtain more comprehensive feedback regarding linguistic clarity and item interpretation. Participants were asked to report any difficulties in understanding the items or response options, and minor wording adjustments were made based on their feedback (11).To assess test-retest reliability, participants completed the questionnaire a second time after a 72-h interval. Although COSMIN guidelines commonly recommend an interval of 7 to 14 days between administrations, shorter intervals may be appropriate when evaluating conditions such as neck pain that may fluctuate over time. The 72-h interval was therefore selected to minimize the risk of clinical changes in symptom severity while still reducing the potential influence of immediate recall of previous responses.Data analyses were performed using Statistical Package of Social Science (SPSS) v.26, with statistical significance set at p 1) and examination of the scree plot, in accordance with commonly accepted practices in psychometric validation (15,16).Internal consistency was assessed using Cronbach's alpha. Testretest reliability was measured with the two-way mixed-model Intraclass Correlation Coefficient (ICC 2,1 ) with absolute agreement and a single score. The ICC ranges from 0.00 to 1.00, with values between 0.60 and 0.80 indicating good reliability, and values above 0.80 reflecting excellent reliability (17).An α value less than 0.70 indicates low consistency, a value between 0.70 and 0.80 reflects moderate consistency, and a value greater than 0.80 represents good internal consistency (18,19).The standard error of measurement (SEM) was computed using the square root of the mean squared error (√MSE) derived from the analysis of variance employed in calculating the intraclass correlation coefficient (ICC). The minimal detectable change (MDC) at a 95% confidence interval (CI) was determined using the formula: SEM × √2 × 1.96 (20,21).Additionally, both SEM and MDC were expressed as percentages relative to the sample mean, denoted as %SEM and %MDC, respectively.Floor and Ceiling Effects was assessed by calculating the percentage of respondents scoring the minimum 0 or maximum 50 total Frontiers in Medicine 04 frontiersin.org score. Effects were considered significant if >15% of participants scored at either extreme.A total of 566 participants were included in the study. The sample consisted predominantly of females (n = 400, 70.7%), while males represented 29.3% of the participants (n = 166). The mean age of the sample was 30.86 ± 13.51 years. The mean body weight was 68.26 ± 14.75 kg and the mean height was 168.76 ± 8.83 cm, corresponding to a mean body mass index (BMI) of 23.9 ± 4.5 kg/m 2 .Regarding clinical characteristics, the mean neck pain intensity score was 1.67 ± 0.47. Based on pain duration, 189 participants (33.4%) reported acute neck pain (12 weeks).In terms of educational background, most participants held a bachelor's degree (65.2%), followed by a master's degree (13.4%), while smaller proportions reported college education or doctoral degrees. The sample included individuals from a wide range of professional backgrounds, with students, physiotherapists, economists, and managers representing the most frequent occupational categories.As per exploratory factor analysis (EFA) of ANDI Items the suitability of the dataset for factor analysis was confirmed by Kaiser-Meyer-Olkin (KMO) measure = 0.947, indicating excellent sampling adequacy. Values above 0.90 are considered superb, suggesting that the correlation patterns are compact and factor analysis is appropriate. Bartlett's Test of Sphericity was significant (χ 2 = 3686.060, df = 45, p excellent internal consistency > and a unidimensional factor These support the use of the ANDI in both clinical practice and accurate evaluation of neck disability and facilitating international across validated NDI The rigorous and participation the and relevance of this tool in the Albanian healthcare the ANDI psychometric properties that are to or than those reported in previous cross-cultural excellent reliability, internal consistency, and unidimensional its suitability for use in clinical and research to assess neck disability among Albanian-speaking suggest that the ANDI the and measurement of the original while culturally and adapted to the Albanian the support the that the ANDI is a tool for evaluating neck disability and is for use in both clinical practice and research across Albanian-speaking populations.
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