Conceptual issues in developmental screening and assessment.

Effective screening requires an understanding of underlying conceptual issues and their relationship to pragmatic concerns. Pragmatic concerns include the concepts that there are many underlying reasons for an "abnormal" screening result; that sensitivity and specificity should be combined with relative risk when considering developmental outcome; and that patterns of congruence among motor, language, cognitive, and adaptive/personal social areas of development should be considered. Important conceptual issues include the following: there is continuity of underlying processes or functions in development; canalized behaviors might give the appearance of discontinuity; integrated functions are more predictive of later developmental levels than are individual functions; the "window" of assessment and the developmental emergence of a specific function will affect screening results; one must consider biologic and environmental risks and their specific effects; and different types of neural structures and their relationship to environmental input help to explain why screening results vary over time.