TABLE 6:

Mean full-scale intelligence quotient in children with sickle cell disease

Test Instrument	Patient Score	No.	Control Score	No.	Reference
WISC-R	88.8	126			Armstrong et al., 1996
	77.7	21	94.3	21	Swift et al., 1989
	82.7	43	88.0	30	Wasserman et al., 1991
	72.3	28	73.5	19	Knight et al., 1995
	85.7	31	92.0	31	Noll et al., 2001
	85.4	15			Present study
WISC-III	82.8	165			Wang et al., 2001
	83.9	156	90.3	76	Bernaudin et al., 2000
	81.8	41			Brown et al., 2000
	86.0	30	92.1	15	Watkins et al., 1998
	78.0	34			Present study
Weighted mean	83.6		89.1

Note.—Mean full-scale intelligence quotient for 690 patients with sickle cell disease, as compared with 192 control participants. Data are from testing of patients and age- and race-similar control participants with the WISC-R or WISC-III. The weighted mean is an average of data from all studies, weighted for the number of study participants in each of the studies. If a conservative assumption is made that the SD of patient and control scores is ± 15, as in Wechsler normative data, then the difference in weighted mean between patients and control participants is significant (P < .000003). To be even more conservative, we then excluded studies that did not include control data collected concurrent with patient data or that derived control data from non-siblings, and we assumed that the sample size of patients was equivalent to the sample size of control participants. This left four studies (underlined), with a sample size of 142 patients and 142 control participants; the full-scale intelligence quotient difference between patients and control participants was still significant (P < .00001).