A 6-month-old infant is able to lift the head while lying on the stomach, then roll over, and eventually sit with support. This sequence BEST demonstrates which principle of growth and development?

A. Genetic testing for CFTR mutations is incorrect as the primary diagnostic tool. While genetic testing can identify specific CF mutations and is useful for screening or confirming atypical cases, it is not considered the first-line gold standard for diagnosis.

B. Sweat chloride test is correct. The sweat chloride test measures the concentration of chloride in sweat, which is abnormally elevated in individuals with cystic fibrosis due to defective CFTR channels. A chloride concentration ≥60 mmol/L on two separate occasions confirms the diagnosis. It remains the gold standard diagnostic test for CF in children.

C. Chest x-ray is incorrect because it is not diagnostic for CF. Although chest x-rays may show structural lung changes such as hyperinflation or bronchiectasis in advanced disease, they cannot confirm CF on their own.

D. Pulmonary function tests (PFTs) are incorrect for initial diagnosis in young children. PFTs assess lung function and disease progression but are not reliable for confirming CF, especially in a 3-year-old who may not be able to perform the maneuvers required.

A. This scale asks the child to verbally rate their pain on a scale from 0 (no pain) to 10 (worst pain). It requires understanding of numbers, abstract thinking, and the ability to quantify pain, which is beyond the cognitive level of most 5-year-old preschoolers. Since the child in this scenario has difficulty understanding numbers, using the NRS would likely lead to inaccurate or unreliable pain assessment.

B. The VAS requires the child to mark a point along a continuous line representing pain intensity, usually anchored with “no pain” at one end and “worst pain” at the other. This tool requires abstract thinking, spatial awareness, and fine motor skills, which preschoolers may not have fully developed. A 5-year-old may not comprehend the concept of a continuous gradient or how to place a mark accurately, making this scale inappropriate.

C. The FLACC scale assesses pain based on observational behaviors: Face, Legs, Activity, Cry, and Consolability. It is designed for infants, toddlers, or children who are nonverbal or unable to self-report. While effective for behavioral assessment, FLACC does not allow the child to self-report pain, which is considered the gold standard whenever possible. Since this child can speak, the nurse should use a tool that allows self-expression rather than relying solely on observation.

D. This scale presents a series of faces ranging from a happy face (no pain) to a crying face (worst pain). Children point to the face that best represents their pain, allowing self-reporting without needing to understand numbers. It is validated for children aged 4–12 years and is developmentally appropriate for a 5-year-old preschooler. It accommodates children who have difficulty with numerical concepts but can interpret visual expressions of discomfort. Additionally, it encourages active participation in pain assessment, improves communication between the child and caregiver, and can guide pain management decisions accurately.