Internal consistency and validity of the Jebsen–Taylor hand function test in an Italian population with hemiparesis

2.1 Participants

The sample was recruited from September and November 2018 in the Department of Neurology of the Polyclinic Umberto I of Rome and the Rehabilitation Clinic of the Nomentana Hospital of Rome. To be included in the study, participants had to be post-stroke adults with chronic hemiplegia or hemiparesis (at least one year since the acute event); have the ability to understand instructions and perform the scale activities; and have extension of the wrist, movement of the thumb, and at least two phalanges≥10°. Individuals with emotional or psychiatric impairments, as determined by clinical screening, were excluded because of being unable to perform the activities of the JTHFT. All participants were informed about the study, and their interest in taking part was recorded; those who subsequently entered the study gave their written consent before inclusion (Galeoto, De Santis, Marcolini, Cinelli, & Cecchi, 2016; Galeoto, Mollica, Astorino, & Cecchi, 2015).

2.2 Validation procedures

The JTHFT-IT was administered to the study population by two trained raters (an occupational therapists and a physiotherapists) who had previously screened all eligible individuals for their recruitment and applied the inclusion/exclusion criteria. The recruited participants who met the study inclusion criteria were scheduled to undergo one testing session. The testing session included the JTHFT-IT administration, the dynamometer measurement, and the Wolf Motor Function Test (WMFT) for all participants included.

2.3 Instruments

The JTHFT consists of seven unilateral items that are administered using standardized procedures and verbal instructions and are performed first with the non-dominant hand and then with the dominant hand. The functional tasks include writing a 24-letter, third-grade reading difficulty sentence; turning 3”×5” (7.62 cm×12.7 cm) cards in simulated page-turning; picking up small common objects including pennies, paper clips, and bottle caps and placing them in a container; stacking checkers; simulated feeding; and moving light cans and heavier (1 pound) cans. The subtests are scored by recording the number of seconds required to complete each task. Increased time to complete the test is related to decreased hand function. A stopwatch was used to time the completion of each task. Normative data from the original scoring system is available for both dominant and non-dominant hands (Culicchia et al., 2016).

Consistent with previous studies, the instrument used in this study to assess grip strength was the Jamar J00105 (Hamilton, McDonald, & Chenier, 2013), a dynamometer model that calculates the strength of the flexor muscles of the hand. When grip is measured, the arm should be at the patient’s side, with the elbow flexed at approximately 90 degrees and the forearm neutral. The wrist should be neutral, but there should be no more than 30 degrees of extension or 15 degrees of ulnar deviation. When ready, the patient is encouraged to squeeze the dynamometer with maximum isometric effort, which is maintained for about 5 seconds. This instrument is scored using force production in kilograms (0–90) or pounds (0–200).

The culturally adapted Italian version of the Wolf Motor Function Test time subscale (WMFT-IT) was also administered to the population. The current version of the scale includes 17 items: two explore the subject’s strength (strength-based tasks) and the other 15 explore functional ability (function-based tasks). The mean execution time (WMFT-TIME), in seconds, is calculated as the sum of the execution times of the single tasks (each has an upper limit of 120 seconds) divided by the number of tasks. The total score is also referred to as the “functional ability” subscale (WMFT-FAS) score, but this subscale was not considered in this study.

2.4 Data analyses

The reliability and validity of the JTHFT-IT were assessed by following the Consensus-BasedStandards for the Selection of Health Status Measurement Instruments (COSMIN) checklist (Mokkink et al., 2010). The internal consistency was examined using Cronbach’s alpha (α) to assess the interrelatedness of the items and the homogeneity of the scale; the α coefficient must be at least 0.70 to indicate the satisfactory homogeneity of all the items within a scale. Cronbach’s α was calculated separately for the affected and non-affected hand in order to record any difference.

The concurrent validity of the JTHFT-IT was studied by calculating Pearson’s correlation coefficient between the JTHFT-IT and the dynamometer instrument (Cincura et al., 2009). Concurrent validity measures the test against a gold-standard test, and high correlation indicates that the test has strong validity, showing whether a test reflects a certain set of abilities—in this case, time in performing JTHFT-IT tasks and strength. The construct validity of the JTHFT-IT was studied by calculating Pearson’s correlation coefficient between the JTHFT-IT and the WMFT-IT-TIME (Berardi, Dhrami, et al., 2018). Construct validity defines how well a test measures up to its claims; it tests whether the constructs that are expected to be related are, in fact, related. The following ranges were considered in interpreting the results: ρ > 0.70 = strong correlation, 0.50 < ρ < 0.70 = moderate correlation, and ρ < 0.50 = weak correlation. The significance level was set as a p-value less than or equal to 0.05.

All statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS) version 20.0 for Windows. The descriptions of the variables were carried out using frequency tables, means, and standard deviations (SDs).

It was found that the JTHFT-IT is a reliable tool to assess hand performance in people with hemiparesis or hemiplegia after a stroke. The internal consistency of the JTHFT-IT showed values of Cronbach’s α of 0.96 for the dominant hand and 0.92 for the non-dominant hand. The analysis of internal consistency was also considered in relation to the limb affected by hemiplegia or hemiparesis. Table 2 reports the results for the dominant hand in the total population, in participants for whom the dominant hand was affected (plegic or paretic) and in participants for whom the non-dominant hand was affected. Table 3 reports the results for the non-dominant hand in the total population, in participants for whom the dominant hand was affected and in participants for whom the non-dominant hand was affected. In general, it is clear that the affected hand requires a longer time for the execution of the tasks. The JTHFT-IT was found to be a valid tool to assess hand performance in people with hemiparesis or hemiplegia after a stroke. Pearson’s coefficient showed statistically significant values both for concurrent validity (dynamometer) and construct validity (WMFT-IT-TIME), but this was mainly for the dominant hand. All the values are reported in Tables 4 and 5.

4.1 Limits of the study

The present study has some limitations. Consistent with previous studies, grip strength was tested using the Jamar dynamometer, but because we were assessing fine hand use, use of a pinch gauge could also have been interesting. The small subsample of people with a dominant paretic hand represents the main limitation, compromising the possibility of having comparable results for the subsamples. In future studies, the authors recommend that this study could be furthered by the inclusion of a larger subsample of this population. Finally, the authors agree with previous studies that the JTHFT itself has some limitations (Allgöwer & Hermsdörfer, 2017; Artilheiro et al., 2018; Davis Sears & Chung, 2010). The score of the test does not reflect different compensation mechanisms for positioning the upper limb. Hence, it is important to provide appropriate instructions before starting the test and to ask patients to not change their strategy while being tested or, in clinical trials that use the JTHFT score as an endpoint, to not change strategies in follow-up evaluations. Furthermore, patients with moderate-to-severe functional impairment are often not testable with the JTHFT.

4.2 Conclusions

In conclusion, it is possible to state that the JTHFT-IT is a useful scale for assessing the function of the hand in everyday activities in the post-stroke population with chronic hemiplegia or hemiparesis. Even though no test used in isolation can provide a realistic assessment of hand function and it is important to consider the potential usefulness of JTHFT in a battery of tests (van de Ven-Stevens, Munneke, Terwee, Spauwen, & van der Linde, 2009), the JTHFT-IT seems very suitable for clinic assessmentsbecause the objects used in the test can be easily purchased and the implementation of the JTHFT-IT is inexpensive. The instructions are simple and straightforward, and gaining expertise in administering the test is not time-consuming. Another important advantage of the JTHFT scale is the evaluation of movements related to activities of daily living, which makes it an ideal tool for use in a rehabilitation program for people post-stroke to assess the individual at baseline, to register improvements, and as an outcome measure. Finally, given the fact that in the literature there exist plenty of assessment tools, it is extremely important to determine which have better characteristics and have been used more extensively internationally. Having specific information regarding tools’ reliability in the different categories of patients allows researchers and clinicians to choose the right tool among the multitude of existingtools.