Prueba de hipótesis para la resistencia a la compresión del concreto

4E.1 SUMMARY

(1) The statistical model predicting the recovery of visual neglect is based on a representative sample of acute stroke patients, m a k e s c l inical sense, and is a c c u r a t e at the upper range of recovery.

(2) It is less acc u r a t e at the lower end of the range, probably because there were too few such patients to allow more accurate stepwise regression analysis.

(3) The regression equations generated were simple and may enable clinicians to select patients for intensive t r e a t ­ ment of visual neglect.

4E.2 The statistical model

Any statistical model which predicts the outcome of stroke should be b a s e d on a r e p r e s e n t a t i v e sample of patients, give a result that makes clinical sense, and be accurate. Preferably, the resultant equation should be simple and the methods used related to standard clinical practice.

The m o d e l p r o d u c e d by the c u r r e n t study is b a s e d on a sample of stroke patients admitted to a district general hospital. The significant predictive variables included in the model make clinical sense in that the initial severity of visual neglect affects its severity at 3 months and at 6 months. T h e i n f l u e n c e of a n o s o g n o s i a on o u t c o m e is of particular interest. Patients with anosognosia had a sig­ nificantly greater degree of visual neglect (mean VNRI 34%, s.d. 38%) than those without anosognosia (mean VNRI 62%, s.d. 31%; t = 1 2 . 8 7 , df 53, p < 0 .0005). A n o s o g n o s i a m a y

therefore be regarded as an indicator of severe visual

n e g l e c t ( F r i e d l a n d + W e i n s t e i n 1977), a n d hence, p o o r recovery, even though the two deficits have been shown to be clinically dissociable (Bisiach et al 1986a) and even though some p a t i e n t s with a n o s o g n o s i a h a d little visual neglect.

The predictive equations are simple, and are consistent

for both time points. There was good matching of actual

and predicted recovery at the upper range, but less so at the lower range, where prediction of the exact severity of visual neglect in the worst patients was imprecise. This is likely to be because there were too few such patients at 3 m o n t h s t o a l l o w m o r e a c c u r a t e s t e p w i s e r e g r e s s i o n analysis : - only seven patients had a VNRI < 60%, all the

rest, except for one, had a VNRI of at least 75%. This may also explain why the severity of visual neglect in the poor outcome g r o u p t e n d e d to be o v e r - e s t i m a t e d . Some of the inaccuracies in prediction may also reflect the failure to s ta n d a r d i z e rem e d i a l the r a p y in the p o p u l a t i o n studied; hence some patients may have received more treatment for visual neglect than others. The best test of the model 's accuracy would be to carry out the prediction analysis on a new sample of patients. This would also demonstrate that the predictive power of the VNRI was not solely the result of the statistical tautology inherent in its development.

Nonetheless, it is apparent that in most patients visual neglect makes a good recovery . The predictive equations may be of value in trials of intensive treatment of visual neglect, w h e r e they could be u s e d to r a n d o m i z e p a t i e n t s into treatment groups matched according to their prognosis (Section 1.3.2). For example, all but one of those whose VNRI at 3 months was <75% had a predicted VNRI of <75% and it might be from this group of patients that candidates for s uch t r e a t m e n t m i g h t come. H o w e v e r , the c u r r e n t s t u d y demonstrates the difficulty of recruiting sufficient p a ­ tients for such a trial, given the generally good prognosis for the recovery of visual neglect.

4F. PREDICTION OF INDEPENDENCE IN SELF CARE AT 3 AND AT 6