TABLE 4

Rates of Cognitive, Academic, and Behavioral Impairment in the EP/ELBW and T/NBW Cohorts According to T/NBW and WISC-IV Normative Distributions

OutcomeEP/ELBW (n = 189)T/NBW (n = 173)Test for Trend
General cognitive impairment
 T/NBW distribution (106 ± 12)
  No impairment49.287.1χ2 = 52.9, P < .0001
  Mild impairment35.810.0
  Major impairment15.02.9
 WISC-IV distribution (100 ± 15)
  No impairment75.994.1χ2 = 22.7, P < .0001
  Mild impairment17.65.3
  Major impairment6.40.6
Reading impairment
 T/NBW distribution (106 ± 14)
  No impairment71.785.5χ2 = 14.5, P < .001
  Mild impairment19.614.0
  Major impairment8.70.6
 WRAT3 distribution (100 ± 15)
  No impairment81.091.9χ2 = 10.3, P = .001
  Mild impairment14.77.6
  Major impairment4.30.6
Spelling impairment
 T/NBW distribution (104 ± 14)
  No impairment73.589.5χ2 = 16.9, P < .001
  Mild impairment22.99.9
  Major impairment4.30.6
 WRAT3 distribution (100 ± 15)
  No impairment82.794.8Cannot be calculated
  Mild impairment15.15.2
  Major impairment2.20
Arithmetic impairment
 T/NBW distribution (99 ± 14)
  No impairment72.087.2χ2 = 14.8, P < .001
  Mild impairment18.110.5
  Major impairment9.92.3
 WRAT3 distribution (100 ± 15)
  No impairment72.087.2χ2 = 14.8, P < .001
  Mild impairment18.110.5
  Major impairment9.92.3
Behavioral problem
 T/NBW distribution
  Normal59.677.3χ2 = 12.3, P < .001
  Borderline (80th percentile)17.511.0
  Abnormal (90th percentile)23.011.6
 SDQ norms
  Normal71.086.9χ2 = 12.4, P < .001
  Borderline (80th percentile)10.96.4
  Abnormal (90th percentile)18.07.6
  • Data are presented as %, unless otherwise specified. Distribution values are presented as mean ± SD. Mild impairment for cognitive and academic scales refers to standard scores from –1 to –2 SDs relative to the normative or T/NBW distribution. Major impairment for cognitive and academic scales refers to standard scores less than –2 SDs relative to the normative or T/NBW distribution.