TABLE 2:

Psychometric test scores of patients with sickle cell disease stratified by MR imaging findings

Comparison	Normal MR Imaging Findings		Abnormal MRI		Δ	Pooled t Test P <
Comparison	No.	Mean ± SD	No.	Mean ± SD	Δ	Pooled t Test P <
Mean hematocrit	30	25.0 ± 4.8	15	23.0 ± 5.8	−8.0%	NS
Full-scale IQ	33	81.1 ± 11.0	16	78.6 ± 16.1	−3.1%	NS
WISC-R FSIQ	10	83.0 ± 8.0	5	90.2 ± 10.5	+8.6%	NS
WISC-III FSIQ	23	80.2 ± 12.1	11	73.4 ± 15.7	−8.5%	NS
Verbal IQ	23	84.6 ± 12.3	11	74.1 ± 15.2	−12.4%	0.02
Performance IQ	23	78.9 ± 12.5	11	77.5 ± 16.3	−1.8%	NS
WISC-III factor scores
VC factor	22	86.0 ± 12.9	11	74.4 ± 13.5	−13.5%	0.01
PO factor	23	80.0 ± 13.2	11	75.7 ± 16.4	−5.4%	NS
FD factor	22	89.0 ± 11.9	11	86.2 ± 17.2	−3.1%	NS
PS factor	20	85.3 ± 14.0	11	93.7 ± 19.9	+9.9%	NS

Note.—IQ indicates intelligence quotient; WISC-R (FSIQ), Wechsler Intelligence Scales for Children-Revised full-scale intelligence quotient; WISC-III FSIQ, Wechsler Intelligence Scales for Children-Version III full-scale intelligence quotient; VC, verbal comprehension; PO, perceptual organization; FD, freedom from distractibility; PS, processing speed; NS, not significant. When MR imaging findings were used to partition patients into those with normal MR imaging findings and those with abnormal MR imaging findings; few significant differences in psychometric test scores were observed. The Δ value was calculated as the percent reduction in psychometric test scores in the abnormal MR imaging group, as compared with test scores in the normal MR imaging group. A one-way pooled t test was used to test for significance because of a prediction that patients with abnormal MR imaging findings would have lower psychometric test scores. Patients with normal MR imaging findings were not significantly younger than patients with abnormal MR imaging findings, nor was there a significant difference in hematocrit.