Initial validation of the Schedule of Growing Skills (SGS)

Margiad Elen Williams, Judy Hutchings, Tracey Bywater, David Daley, & Chris Whitaker

Background Screening tools are used to identify children with possible developmental delay to enable subsequent more rigorous assessment. Quick, inexpensive, and easy to use. Should be as accurate as possible (sensitivity/specificity > 70% recommended by American Academy for Pediatrics (AAP, 2006)).

The SGS in Wales Welsh Assembly Government introduced their Flying Start (FS) Initiative across Wales. The SGS was chosen as the developmental screening tool to evaluate the FS Initiative. Problems with scoring the SGS identified during the Incredible Years (IY) Toddler trial (Hutchings et al., 2011).

Problems with SGS scoring Windows of assessment vary from one month to 12 months causing sensitivity problems. Score highest item within skill set regardless of performance on other items. Cannot compare between groups or across time.

Aims Scoring problems could be solved by developing a way of scoring SGS to yield a Developmental Quotient (DQ) score. This study aimed to validate both the original and new DQ scoring methods of the SGS against a standardised assessment (Griffiths Mental Development Scales; GMDS) and a screening tool (Ages and Stages Questionnaire; ASQ). Used a two step validation process.

Hypothesis: The new SGS scoring method will show increased concurrent validity than the original SGS scoring method when compared to both a standardised assessment (GMDS) and a screening tool (ASQ).

Step oneAim1: To estimate appropriate cut-off point for the new SGS scoring method using Receiver Operating Characteristic (ROC) curves. Aim2: To determine the concurrent validity of both SGS scoring methods against the GMDS.

Participants Data from recent MRes project (Williams, 2010). 39 children (mean age 31 months). 61:39 male:female ratio.

Measures Griffiths Mental Development Scales (GMDS) Schedule of Growing Skills (SGS)

Step twoAim1: To determine the concurrent validity of both SGS scoring methods against the Ages and Stages Questionnaire (ASQ).

Participants Data from recent IY Toddler trial (Hutchings et al., 2011). 94 children (mean age 22 months). 61:39 male:female ratio.

Measures Ages and Stages Questionnaire (ASQ) Schedule of Growing Skills (SGS)

SGS cut-off AUC Sensitivity SpecificityDQ < 90 .794 90.83 67.88DQ < 85 .779 74.18 81.55DQ < 80 .789 65.83 91.90

Table 1. Results from ROC curves analysis

Development area

SGS scoring Sensitivity (%)

Specificity (%)

Over-referrals (%)

Under-referrals (%)

Locomotor Original 10 98.81 1.06 9.57New (DQ<85) 70 92.86 6.38 3.19

Language Original 50 93.02 6.38 4.26New (DQ<85) 75 83.72 14.89 2.13

Fine motor Original 26.67 92.41 6.38 11.70New (DQ<85) 66.67 77.22 19.15 5.32

Overall Original 28.89 94.75 4.61 8.51New (DQ<85) 70.56 84.60 13.47 3.55

Table 3. Concurrent validity of both SGS scoring methods against ASQ

Development area

SGS scoring Sensitivity (%)

Specificity (%)

Over-referrals (%)

Under-referrals (%)

Locomotor Original 16.67 100 0 12.80New (DQ<85) 83.33 51.52 41.02 2.56

Personal-Social

Original 0 100 0 7.69

New (DQ<85) 66.67 100 0 2.56Language Original 20 100 0 10.26

New (DQ<85) 80 94.12 5.13 2.56Fine motor Original 0 100 0 7.69

New (DQ<85) 66.67 80.56 17.95 2.56Overall Original 9.17 100 0 9.61

New (DQ<85) 74.17 81.55 16.03 2.56

Table 2. Concurrent validity of both SGS scoring methods against GMDS

ResultsStep oneAim1: Most appropriate cut-off for the new SGS scoring method is DQ<85 (Table 1).Aim2: New SGS scoring method shows increased concurrent validity than the original scoring method when compared to GMDS (Table 2).

Step twoAim1: New SGS scoring method shows increased concurrent validity than the original scoring method when compared to ASQ (Table 3).

ConclusionsFindings New SGS scoring method shows increased sensitivity, comparable specificity, higher over-referrals, and lower under-referrals. Overall, the new SGS scoring methods reaches the AAP recommended psychometric criteria of sensitivity and specificity levels of 70% or more.Limitations Both data sets used had relatively small sample sizes. Both researchers who collected data for each of the studies had undergone GMDS training which may have affected the way they administered the SGS.Implications Using the new scoring method could lead to increased detection rates. The new scoring method would be of better use in clinical practice and research compared to the original scoring method.

For more information, contact Prof Judy Hutchings, Nantlle Building, Normal Site, Bangor University, LL57 2PZ or email: j.hutchings@bangor.ac.uk