Inter-instrument reliability of pinch strength scores

The consistency of pinch scores obtained with new devices compared with that of scores obtained by traditional devices underlies the ability of therapists to use new devices when communicating about patient status or using normative data published for these traditional devices. This study determined the inter-instrument reliability of pinch strength scores obtained using three commercially available pinch gauges (B&L, JTech and NK pinch gauges). Volunteers (average age, 32 years; range, 18 to 80 years; 19 women, 21 men; 20 with hand pathology, 20 without hand pathology) were tested on a single occasion using all three devices. Each subject was tested with the elbow at 90%, the forearm neutral, and the wrist in neutral deviation. Three trials of maximum tripod and key pinch strength were performed. The hand tested first and the instrument order were randomized. Intraclass correlation coefficients (ICCs) and their 95% confidence intervals were calculated. The inter-instrument error and its associated boundaries (+/- 2 SD) were also calculated. Intraclass correlation coefficients were high for both affected and unaffected hands in patients (> 0.90) and in subjects without pathology (> 0.80). Average instrument error was close to zero and was similar between instruments, indicating a lack of instrument bias. These results suggest that pinch strength scores obtained with any of these three pinch gauges can be compared with normative data obtained with either of the other pinch gauges.