A computerized test’s “ADHD Confidence Index” can identify an ADHD-like performance profile without establishing a clinical diagnosis. A 2013 study of prenatal methamphetamine exposure illustrates that distinction, as well as the difference between an odds ratio and an individual probability.
What population and test were studied?
Kiblawi and colleagues assessed 301 children at approximately 5.5 years: 153 with prenatal methamphetamine exposure and 148 comparisons. These children came from the 412-pair IDEAL cohort, with exposure identified through maternal report and/or confirmed meconium analysis.
Masked examiners administered the Conners’ Kiddie Continuous Performance Test, or K-CPT. During this 7.5-minute computerized task, children responded to pictures except a ball. The test varied presentation intervals and measured errors, response times and changes in performance over the session.
What does the confidence index represent?
The index combines performance features to describe similarity to an ADHD-related test profile. The study treated a score greater than 50% as a positive index result. That threshold is not a finding that a child has a greater-than-50% independently verified probability of ADHD in this particular population.
The analysis did not establish ADHD diagnoses for the children through a separate diagnostic reference assessment. Consequently, index positivity should not be relabeled as confirmed ADHD prevalence or as the fraction of exposed children who inevitably develop the disorder.
How many children exceeded the threshold?
Forty-one of 153 exposed children, 26.8%, exceeded the threshold, compared with 22 of 148 comparisons, 14.9%. These are the observed group proportions for the index endpoint.
The adjusted odds ratio was 3.1, with a 95% confidence interval of 1.2–7.8 and p = 0.02. That estimate concerns adjusted odds of crossing the test threshold. It is not a 3.1-fold increase in every child’s probability, a 310% diagnosis rate or proof that prenatal exposure caused the result. The broad interval also reflects uncertainty about the magnitude.
Were all attention measures different?
No. After adjustment, the groups did not differ significantly in omission errors, commission errors, overall hit reaction time or perseverations. Significant findings involved change in reaction time across blocks and change in reaction-time variability with longer presentation intervals.
Thus similar overall speed could coexist with different performance trajectories as the task progressed or its timing changed. Describing the children as uniformly slower, more error-prone or impulsive would erase the study’s null findings and the specificity of its positive results.
What did adjustment address, and what remained?
Models incorporated other prenatal substances, child characteristics, study site and several caregiver and home measures. Forty-eight home-environment scores were missing; the investigators used multiple imputation and reported similar findings in sensitivity analyses with and without those imputed values.
Parental ADHD was not included as a covariate. The authors also cautioned that the K-CPT was less extensively established in this young, higher-risk population than some instruments used in older children. Enrollment exclusions and incomplete follow-up constrain generalization. Statistical adjustment cannot rule out all shared familial or environmental explanations.
Is this independent of the inhibitory-control study?
No. The Hearts and Flowers analysis examined an overlapping IDEAL cohort at a similar age using a different task and analytic sample. The studies ask different questions but should not be counted as independent population replications.
This study supports a historical association with selected attention-test features and index positivity. It does not validate diagnosing ADHD from prenatal exposure, from a toxicology result or from the confidence index alone, and it does not determine an individual child’s later development.
Source
Kiblawi ZN et al. The Effect of Prenatal Methamphetamine Exposure on Attention as Assessed by Continuous Performance Tests: Results from the Infant Development, Environment, and Lifestyle (IDEAL) Study. Journal of Developmental & Behavioral Pediatrics. 2013;34:31–37. doi:10.1097/DBP.0b013e318277a1c5. Historical prospective observational cohort assessment.
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