During a routine health assessment, which factor would best indicate that additional testing for a developmental delay in a toddler is needed?

A toddler's developmental milestones are important indicators of their growth and progress. A limited vocabulary for age is a crucial sign that may prompt further evaluation for developmental delays. Language skills are a primary aspect of cognitive and social development in young children. By the age of 2, for example, toddlers typically should be able to use at least 50 words and begin combining them into simple phrases. If a child's vocabulary is significantly below this expected level, it may indicate potential language delays or other developmental issues.

Interventions and support can be crucial during this formative stage to help address any delays and support the child’s growth. In contrast, while inconsistent sleep patterns, difficulty with potty training, and refusal to play with peers can raise concerns, they are not as definitive indicators of a broader developmental delay as limited vocabulary is. Both sleep issues and potty training challenges can vary widely and may reflect personal or environmental factors rather than developmental delays. Refusal to play with peers, while it may suggest socialization issues, doesn't necessarily correlate directly with cognitive or language development problems to the extent that vocabulary does. Therefore, the best indicator for prompting additional testing for a developmental delay is a limited vocabulary for age.