Three acts, one pathway — developmental assessment in clinic

Structured clinical encounter — developmental assessment and communication

This station tests whether the candidate structures developmental assessment correctly, chooses the right tool, interprets a screening result honestly, and escalates regression without prompting. Marks reward the three-acts principle, the M-CHAT-R/F threshold, the standard-score model, and the rule that a positive screen is a referral, never a diagnosis. [1] [5]

Stem

A 20-month-old boy is brought to the outpatient clinic by his mother. He has no words, does not point or show objects, and does not make eye contact. His mother says he used to babble and make a few sounds around 14 months but has become quieter over the last two months. He passed his newborn hearing screen. He is the first child of healthy parents, born at term without complication. The team looks to you. [5]

Candidate tasks

1. Frame the assessment (2 minutes). Explain that developmental assessment is built on three acts — surveillance, screening and diagnostic assessment — and state the screening schedule that applies at this age. [1]
2. Choose and interpret the tool (3 minutes). Perform an M-CHAT-R/F, state the screen-positive threshold (three or more of twenty items, or two or more critical items), and explain that a positive screen is a reason to refer, not a diagnosis. [5]
3. Recognise the red flag (2 minutes). Identify the loss of babble and social engagement as regression, and explain why regression demands urgent diagnostic referral the same week rather than a repeat screen. [5]
4. Order the work-up correctly (3 minutes). Refer for diagnostic developmental and autism assessment, check hearing and vision before cognitive assessment, and begin non-directive early intervention on need. [9]
5. Communicate with the family (2 minutes). Explain honestly that the screen raises concern and warrants a closer look, that regression is taken seriously, and that support begins now. [1]

Examiners' discussion points

• Why three acts and not one? Because surveillance is continuous, screening is scheduled and population-scale, and diagnostic assessment confirms and quantifies; conflating them over-labels the well child and under-detects the unwell one. [1]
• Why is the M-CHAT-R/F result not a diagnosis? Because in a low-prevalence population the positive predictive value is modest; a 2023 meta-analysis found real-world screening accuracy lower than validation figures, so diagnostic confirmation always follows. [10]
• Why escalate regression? Because loss of any acquired skill is never a normal variant, and earlier intervention in autism and developmental disorder improves outcome. [5]
• Why audiology before cognitive assessment? Because unrecognised hearing loss is a reversible mimic of language and social delay; the child passed the newborn screen but acquired or missed hearing loss must still be excluded. [9]

Marking grid (out of 20)