Causal links between multi-domain risk factors and intervertebral disc degeneration: a systematic review and meta-analysis of Mendelian randomization studies.

Screening tools can aid in identifying people who may have a particular condition and facilitate access to diagnostic assessment and treatment []. These tools are only useful if they are valid, an assessment typically made at the time of tool development []. Over time, changes in how a condition is defined, classified, or diagnosed can limit the validity of existing tools. This can be particularly challenging in fields where knowledge of a condition is in the early phases or evolving, or with conditions that are not observable on diagnostic tests (e.g., imaging, bloodwork) and rely on subjective report of symptoms (e.g., mental illness, pain) []. Continuously assessing screening tool validity can be resource intensive and may result in the need for tool revision. This is a significant methodological challenge that is not often addressed in the literature. Since the inception of several screening tools for neuropathic pain (NP) in the early 2000s, there have been significant changes in how NP is defined, classified and diagnosed. The review aimed to critically discuss the challenges in maintaining the validity of NP screening tools alongside this evolving knowledge. To summarize literature on this broad topic and deepen our understanding, a narrative review is appropriate [, ]. To illustrate this challenge, the validity of the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS), a self-report screening tool for NP, was critiqued []. The purpose of the LANSS is to discriminate between people with NP from people with other types of pain, for example, musculoskeletal or inflammatory pain. The LANSS was chosen as it was the first developed tool, recommended by the International Association for the Study of Pain (IASP) [], and has been the most studied []. Both the original (LANSS) and self-report version (s-LANSS) were examined. The most important measurement properties of a screening tool are content and criterion validity (Table ). Content validity, including face validity, refers to the relevance, comprehensiveness and comprehensibility of a tool []. This is established during tool development and through formal testing with patients and clinicians []. During development, the condition and population need to be clearly defined and reflect the current state of knowledge to ensure the tool’s relevance [, ]. If the definition of a condition changes, there may be a conceptual mismatch between an existing screening tool and the contemporary definition. This mismatch can limit the tool’s relevance (includes items that are no longer relevant) or comprehensiveness (important items are missing). These limitations may be readily apparent (face validity) or require formal content validity testing to determine whether tool revision is needed. Content validity is the most important property; if the tool is not relevant or comprehensive, it will compromise other properties including criterion validity [].