The base rates or prevalence of target developmental problems (e.g., developmental delay, autism, language disorders) in your practice are critical in determining the accuracy or predictive values of developmental screening instruments in your setting. In general, the lower the prevalence of delay in a practice, the more accurate (e.g., higher sensitivity and specificity) a screening method needs to be in order to limit the number of false-positive and false-negative results.
How can you identify the base rates of target developmental problems in your practice setting? Clinic records of rates of diagnoses of developmental problems in your practice are one way to identify base rates. However, unless you are routinely screening every child, this may underestimate the true prevalence of developmental problems in your practice. Another way is to estimate the level of biologic/environmental risk for developmental problems experienced by children seen in your practice. The following table can help you determine the level of risk for the prevalence of developmental problems in your practice.
Biologic and Environmental Risk
|Lower risk||Intermediate Risk||Higher risk|