Responsiveness of SF-36 and Lower Extremity Functional Scale for assessing outcomes in traumatic injuries of lower extremities
Introduction
Responsiveness, defined as the ability of a measurement or instrument to detect change accurately when it has occurred [1], constitutes an important features of a valid an outcome measure. It can be assessed by several ways, which are classified by researchers into two major categories, internal responsiveness and external responsiveness [2]. The former category includes paired test and several effective size statistics and is largely based on sample variation. Meanwhile, the latter category includes receiver operating characteristics (ROC) method, correlation and regression models. Using clinical global rating as the anchor in ROC method is preferable for its consideration of patients’ perspectives [3]. Nevertheless, some of the above statistics are dependent on particular purpose with a particular group of subjects. For example, minimal clinical important improvement varies according to the range of scores at baseline, acuity and pain location [4]. Therefore, the context specificity should be considered in clinical application of outcome measure.
Traumatic injuries of lower limbs include a broad spectrums of injury patterns and severity, ranging from abrasion of toes, sprain/strains around a single joint, single or multiple bony fractures, amputation, vascular injuries, nerve injuries to a combination of the above [5], [6]. These injuries had multi-dimensional impact on individual function [7], [8]. In reflection of the heterogeneity of the injury types and severity, either generic or region-specific measures are potentially more appropriate than disease-specific or joint-specific measures for outcome assessment. Among the generic measures, Medical Outcomes Study Short Form-36 (SF-36) and sickness impact profile (SIP) were among the most popular tools for lower limbs trauma or amputations [9], [10]. SF-36 had equal or superior responsiveness to other questionnaires to measure health changes in subjects with musculoskeletal disorders, osteoarthritis or hip fractures [11], [12]. Meanwhile, region-specific outcome measurements also gained popularity in outcome assessment, with especially the advantages of wider application than disease-specific questionnaires and similar validity in comparison with disease-specific or joint-specific measures [13].
Lower Extremity Functional Scale (LEFS) was one of the region-specific measures and developed for lower extremity musculoskeletal disorders. Its responsiveness had been tested in population with single diagnosis, such as hip osteoarthritis [13], ankle fracture [14], post-reconstruction for anterior cruciate ligament [15] and anterior knee pain [16], or with a heterogeneous diagnosis [17], [18]. Nevertheless, it was not used in subjects limited to traumatic injuries so far.
In this longitudinal study, we followed up subjects with lower extremity injuries for 2–3 months. Our goal was at assessing and comparing the responsiveness of SF-36 and LEFS with distribution-based (effect size, standardized response mean [SRM], minimal detectable change [MDC]) and anchor-based approach (receiver's operating curve [ROC] analysis).
Section snippets
Methods
This was a prospective and follow-up study. A convenience sample of subjects with traumatic musculoskeletal disorders of lower extremities was recruited from the orthopaedic wards and rehabilitation outpatient clinics in two university hospitals. They were at between 18 and 80 years old and had no other comorbities which would influence locomotion function, such as cognitive impairment, neurological or cardiopulmonary disorders. The study was approved by the ethics committee of National Taiwan
Results
One hundred and nine subjects were evaluated at baseline and 94 (86%) were followed up in 64.3 (standard deviation 25.9) days. Un-followed subjects were more likely to be older, have higher baseline LEFS score and have higher proportion receiving operation than the followed cases (Table 1). Otherwise, the followed and un-followed subjects had similar demographic features. More than 80% of the participants had disease duration of less than 30 days and 70%, receiving surgeries within 2 weeks.
Discussion
The responsiveness of one generic measure, SF-36, and one region-specific measure, Lower Extremity Functional Scale (LEFS) was assessed among a group of subjects with traumatic lower limb injuries. Our findings suggested that LEFS and physical component score (PCS) subscale had comparable internal responsiveness in a 3-month follow up. Like other measurement characteristics, responsiveness is not a constant characteristic of a measure. It can be evaluated only when a measure is used for a
Conclusion
Our findings revealed comparable responsiveness of LEFS and PCS of SF-36 in a sample of subjects with traumatic injuries of lower limbs. From a psychometric perspective, either SF-36 PCS or LEFS would be suitable for use in clinical trials where improvement in function was an endpoint of interest.
Conflicts of interest
All authors disclose no financial and personal relationships with other people or organizations that could inappropriately influence the work. There was no potential conflict of interest, including employment, consultancies, stock ownership, honoraria, paid expert testimony, patent applications/registrations, and grants or other funding.
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2021, InjuryCitation Excerpt :The reported SDC values of the LEFS show much variation (ranging from 2.18 for Spanish LEFS scores in patients diagnosed with lower extremity musculoskeletal conditions [37] to 18.1 in patients with knee osteoarthritis [38], as displayed in the systematic review by Mehta et al. [12] All values are much lower than the SDC found in the current study (SDC 38.74). Explanations for this difference include more heterogeneity of the patient population [36,37], shorter follow-up time [36,37,39], and smaller sample size. [40] The most important clinimetric property for interpreting change over time is the minimum important change (MIC).
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