The diagnosis of rhizarthrosis is based on clinical signs and symptoms confirmed by imaging exams. The clinical condition of rhizarthrosis is characterized by progressive pain, limitation of pinch activities involving the thumb, edema at the base of the thumb, apparent angular deviation and crackling [19]. However, Baker et al. in reviewing the evidence-based literature observed that most of the patients with radiological images of rhizarthrosis are asymptomatic. The alterations found in the imaging exams do not always correspond to the clinical condition presented, that means, patients with typical alterations in the imaging exam may have mild symptoms or even be asymptomatic [20, 21].
Self-assessment questionnaires have been used in the literature to evaluate treatment results for different health problems. The translation and cultural adaptation to Brazilian Portuguese makes it possible to use these instruments in Brazil [22,23,24]. In search for a more specific tool, questionnaires have been described to evaluate the pain intensity and the functional limitation caused by rhizarthrosis. In 2007, the Nelson Score was described, which presents 10 questions about daily activities of living, with the objective of evaluating the surgical results of rhizarthrosis [9]. In 2016, the Thumb Disability Exam (TDX) was described, which consists of 20 questions. During the translation and validation process, it was considered reproducible for Brazilian Portuguese (TDX-BR), although difficulties in understanding some questions have been described, according to the translators [13]. In the description of the TASD, Becker et al.considered to be a simple and self-administered scoring system and was considered concise and useful in the evaluating of symptoms and disability related to rhizarthrosis [20]. In our paper, the application of the translated and validated TASD-BR to patients did not present any difficulty in understanding. We consider this questionnaire to be more concise and simpler, even though it maintains a good linear correlation with the TDX-BR. The time to complete the questionnaire was not measured, but because there are eight questions less than the TDX-BR, we deduce to be shorter.
Following the recommendations of Matsuo et al., we chose to keep the page in vertical format, as it facilitates understanding in the Brazilian socio-cultural context [25].
The method used to apply this questionnaire should be considered as a limitation factor. The first application was done personally with all the patients. The second application was carried out through telephone or e-mail contacts. We only had personal interviews with 2 patients who did not know how to read. This is used to prevent social exclusion of patients due to low education levels which could lead to reduction of the sample [26, 27]. Furthermore, many patients had financial limitations to move back to the hospital to a new evaluation. Since we never experienced or witnessed any difficulty in understanding the questionnaire during the first application, we considered that the second method of data collection could not result in significant results discrepancy.
For the TASD-BR questionnaire, and even when separated by subdivisions "symptoms" and "ability to perform activities", high internal consistency was found, with α ≥ 0.70, and notable ceiling and floor effect were not observed. Internal consistency is the measurement property that assesses the ability of a questionnaire to measure a single concept using multiple items, or even evaluating it in subdivisions. Therefore, it is extremely important that this value is high, as they denote specificity in testing a construct.
We chose the interval of 2 to 4 weeks between the test and the re-test. This interval should be sufficient to avoid any change in symptoms or progression of the disease, neither for the patient to be able to remember the answers that he had answered in the previous questionnaire [18]. The questionnaire showed high reliability. Intraclass correlation coefficient (ICC) values greater than 0.60 are considered to be a good correlation. In our study, this value was κ = 0.961 (0.954–0.967). These values denote a high correlation between test and retest and demonstrate that the questionnaire is reliable in reproducing symptoms.
Agreement, measured using the SEM, was considered to be good (< 10%) or very good (< 5%). The questionnaire had a high correlation between the test and the retest, with κ = 0.961 (0.954–0.967). All variables maintained the same pattern when compared to the original questionnaire [10, 17, 18].
Construct Validity measures the relation of a new instrument with other instruments that theoretically assess similar hypotheses and concepts. As there was no description of a specific gold standard questionnaire for rhizarthrosis, the original TASD questionnaire maintained a linear correlation with The Disabilities of Arm Shoulder and Hand Score (DASH), Patient Health Questionnaire-9 (PHQ9) and Pain Self Efficacy Questionnaire (PSEQ) [10, 14]. In our research, the construct validity was measured by the correlation between the results of the TDX-BR questionnaire, previously translated [13]. A linear relation was found between the two questionnaires. This means that high scores on the TDX-BR must correlate with high scores on the TASD-BR, and vice versa. This correlation denotes efficiency in the two scores in measuring the same construct [15, 17, 18].
Although the disease was more prevalent in the non-dominant hand, the difference was not significant, and no correlation was found in the TASD-BR scores considering that. Thus, we conclude that this fact should not be considered as bias.
