Introduction Patellar tendinopathy (PT) is a common chronic tendon degeneration process, the precise aetiology of which remains unclear.1 Numerous risk factors have been identified in the development of PT, such as sport played and reduced quadriceps flexibility.2 The VISA-P is a validated questionnaire for assessing the severity of PT only and is commonly used as the primary outcome in PT research.3 Our study aim was to evaluate the equivalence of self-administration of the VISA-P online, with the addition of risk factor questions, to clinician administration in order to develop a tool suitable for high-volume remote use.
Methods The questionnaire was developed online to allow remote access whilst ensuring confidentiality and anonymity (available at http://patellartendinopathyquestionnarie.blogspot.com/) A literature search, combined with clinical experience from leading experts in tendinopathy, was used to determine the risk factor questions that should be included in the study. A crossover study design with 108 subjects was used to determine equivalence between online and clinician administration. Three population groups (controls, at risk and clinically diagnosed PT) were used to ensure construct validity.
Results Online versus clinician-administration revealed an intra-class correlation (ICC) of 0.79 (CI: 0.68–0.86) for the VISA-P with a systematic significant difference of 4.99, which is not clinically meaningful. Poor ICCs were seen for questions 7 and 8 of the VISA-P (0.37 and 0.47 respectively) in comparison to earlier questions. There were statistically significant differences between populations groups for the VISA-P. The ICC for risk factor questions was excellent at 0.89 (CI: 0.84–0.93) with no mean differences (p = 1.00).
Discussion The online questionnaire enables equivalent collection of VISA-P data and risk information without technical difficulty. The ICC of 0.79 for the VISA-P administration methods is considered equivalent.4,5 The sub-analysis of the VISA-P questions showed where the small difference in means arose: questions 7 and 8. The explanation for this appears to be multifactorial and minor modifications have since been made to ensure clarity, especially for control subjects who appeared to misunderstand being unable to compete in sport due to pain from PT from not wanting to or not having time. The risk factor ICC both overall and for individual questions was excellent.
Therefore, there is the potential to use this questionnaire electronically to generate a large database of risk factors to understand better the correlation between risk factors and PT development. From this it is hoped that prevention, interventions and treatment can all be improved.
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