The Corbett Targeted Coin Test: Reliability, criterion related validity, and normative data

Study Design: Clinical measurement. Background: Many daily living tasks require in-hand manipulation (IHM). There is a gap in standardized assessment tools for measuring IHM. The Corbett Targeted Coin Test (CTCT) was designed to allow measurement of that fine motor skill. Purpose: 1) To evaluate the interrater, test-retest reliability, and validity of the CTCT, and 2) to establish adult norms for the CTCT. Methods: Reliability and Validity – 30 participants (25 females, age range 21–45) were assessed with the Nine-Hole Peg test and CTCT consecutively by three researchers, then re-evaluated one week later on the CTCT; Reliability was determined using intraclass correlation (ICC_2,k) between tests and across testers; Criterion-related validity was determined by comparing scores from nine-hole test and CTCT across testers using ICC_2,k. Normative – 190 participants (147 females, age range 20–80) were assessed with the CTCT; mean and standard deviation for participants’ scores were calculated by age groups and gender. Results: Test-retest reliability: poor for the right hand (ICCs = −0.29 to 0.45), and poor-moderate for the left hand (ICCs = 0.17–0.56). Inter-rater reliability ranged from moderate to excellent (ICCs = 0.60–0.80). The agreement between CTCT scores and Nine-Hole Peg test was poor for the right (ICC = 0.02; 95% CI: [−0.06, 0.14]) and left hands (ICC = 0.06; 95% CI: [−0.08, 0.28]). CTCT normative data: 41–50 age group demonstrated the highest performance while the 71–80 age group demonstrated the lowest performance. Scores between genders were similar. Discussion: The poor test-retest reliability of CTCT was probably due to practice effect, while interrater reliability indicated that the test can be administered by different testers without compromising the results. The poor validity between tools proves their different constructs. Conclusions: Use of the CTCT may add another dimension to assessment of dexterity and fine motor skills, specifically, in-hand manipulation, but needs further research on test-retest reliability.