Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made.  (Formerly, these situations were captured under a "C Recommendation".)  This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade.  For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.

Overview
Preschool screening is directed at children 3 to 5 years of age and entails early detection of cognitive and behavioural problems that could jeopardize school performance. We evaluated primarily those screening tests that can be used in the primary care physician’s office or in a relatively small system of care.<1> Remedial intervention for identified problems is usually carried out by professional educators, but often involves other health professionals such as speech and language therapists and occupational therapists. Early detection of developmental problems using the Denver Developmental Screening Test (DDST) has been shown not to improve school performance but to increase parental anxiety and is therefore not recommended. However, the benefits of other screening tools and remedial programs are controversial.

Burden of Suffering
Good data describing the prevalence of school performance problems are difficult to find. The reported prevalence has varied from 6% to 30%; an arguable estimate is 16% to 20%. The rates have depended on factors such as the socioeconomic status of the population studied (children in lower socioeconomic groups tend to have more difficulties), the definition of school problems and the stage in the educational process at which an outcome is measured. The impact of poor school performance on the child and family can be wide-ranging and difficult to measure, but since society values education and school performance highly this problem has received much attention.

Maneuver
Measurement instruments have generally not been adequately evaluated for screening purposes. Sensitivity and specificity as well as predictive values for many instruments have been assessed through multiple analyses of one data set without testing the instrument on another population to confirm the findings.

The DDST is the most widely used test.<2> It is relatively easy to perform, takes little time and is inexpensive. It is effective among children with intelligence quotients (IQs) of less than 70, but its ability to identify less severe or specific developmental problems has been questioned. The reported sensitivity and specificity have varied considerably; in one study they were 29% and 89% respectively,<3> whereas in another they were 5% to 10% and 99%.<4> With an assumed prevalence rate of 20% the positive predictive value (proportion of true positive results) is 71% and the negative predictive value (proportion of true negative results) 81%; because of its low sensitivity, however, the DDST fails to identify 90% to 95% of children with developmental problems.

A revised version of the Denver Scale, the Denver-II, has added 20 new items primarily focusing on language expression and skills of articulation. There is, however, limited evidence to support its validity and indeed, work by Glascoe et al (1992),<5> raises serious concern regarding the sensitivity and specificity of the new version.

The Developmental Indicators for the Assessment of Learning<6> constitute a multi-dimensional instrument that reflects the school behaviour expected of children in a regular classroom setting. The instrument appears to have considerable potential (sensitivity 46% to 54% and specificity 93%<3>), but more research is required to establish its reliability and validity. Since a team of five to eight people and a moderate amount of equipment are required to administer the test its use is inappropriate for primary care physicians.<7>

The Early Screening Inventory<8> measures developmental abilities, is relatively easy to administer, takes 15 to 20 minutes to perform and has a high sensitivity (81% to 100%) although a lower specificity (67% to 72%).<9> Health care professionals could potentially administer the test, but the reliability of the results depends on the training of the examiner.<8>

The Minneapolis Preschool Screening Instrument<10> is educationally oriented, brief and economical to administer and has achieved a sensitivity of 60% to 63% and a specificity of 89% to 93%.<11> It shows promising reliability and validity.<10> Other instruments such as the McCarthy Screening Test<12> and the Jansky Screening Index (JSI)<13> need further validation. A study using the JSI assessed teachers’ ratings of overall reading skills in grade 1 against outcome in grade 2.<14> The teachers’ ratings had both a sensitivity and a specificity of 93%, as compared with 50% and 90% to 92% respectively for the JSI. Furthermore, the teachers’ assessments of children in grade 1 had a sensitivity of 61% and a specificity of 86% when compared with school performance in grade 6. The suggestion that the teacher is the best early identifier of future school problems has also been supported by other studies.<15>

Effectiveness of Prevention and Treatment

Denver Developmental Screening Test
The only randomized controlled trial that examined the effectiveness of developmental screening and treatment encompassed three school districts and 4,761 children in the Niagara region of Ontario.<16> The control group comprised children who did not undergo the DDST (18% of the subjects). The remainder were randomly allocated to undergo the DDST with or without an intervention for those with positive results. The intervention consisted of referral to the child’s physician for assessment, parent counselling, a review conference between the child’s teacher and the school nurse, and monitoring of the child in school by the school nurse.

The children with positive results were assessed by various outcome measures such as the use of specialized educational services, academic achievement, cognitive and perceptual motor tests, and assessment of behavioural, social and emotional well-being. There were no statistically significant differences in outcome between the two screened groups; however, there was a statistically significant increase in worry about school work among the parents of the children in the intervention group. Since there was no benefit from the screening program and a potentially harmful labelling effect we caution against the widespread use of the DDST for screening purposes.

Intervention
Very few studies of specific interventions to improve problems such as reading performance were of sufficient methodologic quality to warrant consideration. However, some insight may be provided by a study of reading performance in older children (mean age 10.2 years) who had been referred by teachers because of poor academic performance.<17> Sixty-one children were randomly assigned to a control group or to a motivated remedial reading group in which each child received 54 sessions over 18 weeks. The intervention group obtained significantly higher scores in all reading tests than the control group did. However, the effect was transient, and the teachers did not rate the children in the intervention group as being significantly improved in general academic performance. Although these results are promising they do not provide sufficient evidence for a generalized adaptation of this strategy as an intervention, particularly among younger children.

Large-scale community programs aimed at high-risk or disadvantaged groups have resulted in mixed and controversial findings. These programs have often been characterized by early optimism followed by disappointment.

Information on the Head Start programs in the U.S. is extensive and open to multiple interpretations. Meta-analysis showed that significant and immediate gains in cognitive test scores, socio-emotional test scores and health status were achieved but the improvements were not long-lasting.<18> These findings have been disputed by others.<19>

In the Perry Preschool Program<20> disadvantaged children in Michigan received early intervention. Although conclusions about the effectiveness of the program remain controversial, at least one reviewer has argued that, in the long term, treated children had better school attendance, needed fewer special education services, were more likely to graduate and had lower rates of school drop-out, delinquency and teenage pregnancy than untreated children.<19> (Other evidence on disadvantaged children is reviewed in Chapter 32.)

Recommendations of Others
In 1986 the Committee on Children with Disabilities of the American Academy of Pediatrics (AAP) recommended that all children attending school be examined for developmental disabilities, preferably by their own pediatrician, before the time of registration or entrance to school. AAP includes elements of developmental screening in its recommended behavioural assessment at preschool visits.

Conclusions and Recommendations
There is fair evidence to recommend the exclusion of the Denver Developmental Screening Test (DDST) from the periodic health examination of asymptomatic preschool children (D Recommendation).

There is insufficient evidence to support either the inclusion or exclusion of other screening instruments (C Recommendation). Caution is advised, however, since problems exist with all current assessment tools, and no interventions have been conclusively proven to be effective. Large-scale community programs to prevent poor school performance in high-risk or disadvantaged groups have also given mixed and controversial results.

Unanswered Questions (Research Agenda)
The following have been identified as research priorities:

Assessment by teachers of children in kindergarten and grade 1 should be compared with preschool screening by health care professionals. The risk of teacher bias and the harmful effect of labelling students as having developmental problems should be studied.
Developmental screening instruments of acceptable quality need to be developed and evaluated.
Given the high costs associated with early education interventions, carefully designed and more focused studies should assess the effectiveness of remedial intervention once problems are identified.

This review was initiated in January 1993 and updates a report published in December 1989.<1> Recommendations were finalized by the Task Force in March 1993.

Full Citation
Feightner, J.W. Preschool screening for developmental problems. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994; 290-296.