FIM-Minimum Data Set Motor Item Bank: Short Forms Development and Precision Comparison in Veterans.

OBJECTIVE

To improve the practical use of the short forms (SFs) developed from the item bank, we compared the measurement precision of the 4- and 8-item SFs generated from a motor item bank composed of the FIM and the Minimum Data Set (MDS).

DESIGN

The FIM-MDS motor item bank allowed scores generated from different instruments to be co-calibrated. The 4- and 8-item SFs were developed based on Rasch analysis procedures. This article compared person strata, ceiling/floor effects, and test SE plots for each administration form and examined 95% confidence interval error bands of anchored person measures with the corresponding SFs. We used 0.3 SE as a criterion to reflect a reliability level of .90.

SETTING

Veterans' inpatient rehabilitation facilities and community living centers.

PARTICIPANTS

Veterans (N=2500) who had both FIM and the MDS data within 6 days during 2008 through 2010.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Four- and 8-item SFs of FIM, MDS, and FIM-MDS motor item bank.

RESULTS

Six SFs were generated with 4 and 8 items across a range of difficulty levels from the FIM-MDS motor item bank. The three 8-item SFs all had higher correlations with the item bank (r=.82-.95), higher person strata, and less test error than the corresponding 4-item SFs (r=.80-.90). The three 4-item SFs did not meet the criteria of SE <0.3 for any theta values.

CONCLUSIONS

Eight-item SFs could improve clinical use of the item bank composed of existing instruments across the continuum of care in veterans. We also found that the number of items, not test specificity, determines the precision of the instrument.