Key Neurological Impairments Influence Function-Related Group Outcomes After Stroke

Abstract

Background and Purpose — The function-related group (FRG) classification is based on functional assessment and has been assumed to encompass the effects of different patterns and severity of neurological impairments. This assumption may not be correct. It has been proposed as a means of comparing rehabilitation outcome across institutions. If neurological impairments significantly affect FRG outcome, then higher FRG outcome scores may reflect selection bias favoring patients with fewer neurological impairments rather than better quality of rehabilitation care. The goal of this study was to assess the influence of motor, somatosensory, and hemianopic visual impairments on FRG outcomes after stroke. Methods — All 288 consecutive stroke patients discharged in 1999 from an acute rehabilitation hospital were assigned to 1 of 5 FRGs on the basis of their Functional Independence Measure (FIM) mobility subscore and age. Each FRG was also stratified into 1 of 4 cohorts on the basis of the presence or absence of key neurological impairments: motor impairment only (M), motor plus either somatosensory or hemianopic visual impairment (MS/MV), motor plus somatosensory plus hemianopic visual impairment (MSV), and other combinations of impairments. FIM scores were available every 10 days for all patients from admission to discharge. The effect of impairment group on outcome was assessed within each FRG category through repeated-measures analysis of variance to assess differences in serial FIM scores across the 4 impairment groups. The distribution of each of the 4 impairment groups across the 5 FRGs was assessed with χ 2 analysis. Results — The numbers of patients in each of the 5 FRGs from the lowest level, FRG-11, to the highest, FRG-15, were as follows: 78 (27%), 47 (16%), 75 (26%), 55 (19%), and 33 (11%). Different neurological impairments were associated with significantly different mean±SD discharge FIM scores as follows: for FRG-11, MSV=63±16, MS/MV=68±19, and M=81±13 ( P =0.04); for FRG-12, MSV=47±14, MS/MV=61±12, and M=75±11 ( P =0.01); and for FRG-13, MSV=79±20, MS/MV=85±19, and M=96±10 ( P <0.02). For FRG-14 and FRG-15, those with M impairments had the highest and those with MSV impairments had the lowest discharge FIM scores, but the differences did not reach statistical significance. The χ 2 analysis showed a highly significant difference in representation of MSV impairments across FRG-11 through FRG-15 as follows: 35 of 78 (45%), 20 of 47 (43%), 11 of 74 (15%), 4 of 55 (7%), and 2 of 33 (6%). For patients classified as having an M deficit only or other impairment, the results were as follows: 19 of 78 (24%), 15 of 47 (32%), 41 of 75 (55%), 41 of 55 (75%), and 27of 33 (82%) (χ 2 analysis=78.7, P <0.0001). Conclusions — The presence of motor, somatosensory, and hemianopic visual impairment significantly affects FRG outcome and should be included in future outcome assessment tools. Comparisons of FIM change and efficiency scores across institutions are potentially biased by referral and selection criteria favoring equally dysfunctional but less neurologically impaired individuals.