3 December 2012
Morris et al.'s review of the validity of Australian Developmental Screening Test (ADST) is helpful, as the test was standardised two decades ago. The ADST provides a simple, affordable and effective clinical framework for assessing the development of young children. The ADST manual recommends referral for a formal assessment when a child aged over 2 years, scores 4 months less than his chronological age in any one domain or 2 months less in three or more domains (4/2). The Morris et al. study showed improved sensitivity and specificity of the ADST when the referral threshold was doubled to 8/4.
In 2010, the Macarthur Child Assessment Team undertook a similar study of 67 children with suspected developmental disabilities referred by local paediatricians. On the same day children were assessed with the Griffiths Mental Developmental Scales, Extended Revised (GMDS-ER) or the Bayley Scales of Infant Development, Third Edition (Bayley Scales III) and the ADST.
The validity of the ADST in predicting results in standardised developmental assessment scales was determined using the original threshold of 4/2, Morris et al.'s proposed threshold of 8/4 and a threshold of 12/6. ADST results were compared with a GMDS-ER general quotient <80, or one or more of the sub-scale quotients <70. Bayley Scales III overall and domain quotients were generated using age equivalents. Statistical analyses were performed using MedCalc for Windows, version 11.7.90. Approval was received from the Human Research Ethics Committee (Western Zone) of Sydney South West Area Health Service (QA2010/038).
Fifty-five children were assessed with GMDS-ER and 12 children with the Bayley Scales III. The average age was 49 months, ranging from 29–64 months. There were 10 girls and 57 boys in the study. Thirty-three per cent had a mild developmental delay, and 28% had moderate–severe developmental delay. An autism spectrum disorder was diagnosed in 57%. The results obtained for screening thresholds are shown in Table 1.
|Threshold||Sensitivity||Specificity||Positive LR (95% CI)||Negative LR (95% CI)|
|4/2||95||25||1.27 (0.72–2.24)||0.19 (0.03–1.44)|
|8/4||84||20||1.05 (0.67–1.65)||0.81 (0.13–5.09)|
|12/6||77||80||3.87 (0.67–22.46)||0.28 (0.15–0.53)|
Our study supports Morris et al.'s finding that the published referral criteria are not valid in a clinical population. Increasing the threshold to 12/6 maintained the sensitivity and greatly improved the specificity of the ADST. A threshold of 8/4 was sensitive but not specific. We used the recent revisions of the GMDS and Bayley Scales III, and our study included fewer children with normal development. Given the long waiting lists for diagnostic services, we recommend reassurance with a score of 4/2 or better, monitoring or referral at 8/4 and definite referral at 12/6.