Developmental regression — the loss of previously acquired skills — is a neurological emergency until proved otherwise. A child who was saying 10 words at 18 months and has lost them by 22 months is not 'just a bit slow' — this pattern demands urgent investigation. The most important diagnoses not to miss: (1) Landau-Kleffner syndrome (acquired epileptic aphasia) — children typically develop normally until 3-8 years, then lose language due to continuous epileptiform discharges in the temporal language areas during sleep. The EEG during sleep is diagnostic; waking EEG may be normal. Treatment with corticosteroids or antiepileptics can restore language if treated early. (2) Autism spectrum disorder — language regression in ASD typically occurs between 15-24 months (after a period of apparently normal development), often accompanied by loss of social engagement and the emergence of repetitive behaviours. The RCGP curriculum requires GPs to identify developmental regression as a red flag requiring urgent referral.

The distinction between expressive-only delay and receptive-expressive delay is the single most important clinical discriminator in speech delay assessment — a child with pure expressive delay who has age-appropriate comprehension (follows two-step commands, understands complex instructions, responds appropriately to questions) has a much more favourable prognosis than a child with impaired comprehension. Pure expressive delay in boys aged 18-30 months with good comprehension and good non-verbal communication (pointing, gesturing, making eye contact) is often described as 'late talking' — a benign variant that resolves spontaneously in approximately 50-80% of cases. However, even 'late talkers' with expressive-only delay benefit from early speech and language therapy referral because: (1) the GP cannot reliably distinguish pure expressive delay from early receptive delay or ASD in a 10-minute consultation; (2) early SLT input is safe and beneficial regardless of cause; and (3) approximately 20-30% of late talkers will have persistent language problems without intervention.

The M-CHAT-R/F (Modified Checklist for Autism in Toddlers, Revised with Follow-Up) is the validated screening tool for ASD in UK primary care — it is a 20-item parent questionnaire designed for children aged 16-30 months that screens for the core features of ASD. The R (revised) version has improved specificity over the original M-CHAT. The F (follow-up) module provides structured follow-up questions for intermediate-risk scores to reduce false positives. The tool is freely available and takes approximately 5 minutes to complete — GPs should use it at the 2-year developmental review (or any consultation for speech delay in this age group) for all children, not just those with obvious autistic features. A positive screen (medium or high risk) should prompt immediate referral to the ASD diagnostic pathway (community paediatrics or CAMHS) without waiting for speech therapy assessment results. The key scoring: low risk (score 0-2) = rescreen at next routine check; medium risk (3-7) = complete follow-up interview; high risk (8-20) = refer immediately for ASD assessment.

Developmental language disorder (DLD) — previously called specific language impairment (SLI) — is one of the most common neurodevelopmental conditions in children, affecting approximately 7-10% of school-age children. It is defined as a persistent language disorder in a child with: normal hearing, normal non-verbal intelligence, no ASD, no cerebral palsy, and no known genetic syndrome. Children with DLD have significant difficulty with both understanding and using language — grammar, vocabulary, narrative, and phonological processing are all typically impaired. The prognosis is variable: approximately 40% of children with DLD at age 5 have persistent language difficulties at age 15-17. DLD is associated with substantial educational, social, and mental health difficulties in adolescence and adulthood. The RCSLT (Royal College of Speech and Language Therapists) estimates that approximately 1-2 children in every classroom of 30 has DLD. Early identification and intensive SLT input significantly improves outcomes. GPs should be aware that DLD is not a diagnosis of exclusion made in infancy — it requires formal SLT assessment, and the diagnosis is typically established around age 4-5 when non-verbal intelligence can be reliably assessed.

The simultaneous referral principle for speech delay is important — GPs should refer to both audiology and SLT at the same consultation, rather than waiting for audiology results before referring to SLT. The reason: NHS waiting times for both audiology and SLT are often 4-16 weeks. If the GP waits for audiology before referring to SLT, the total delay to first SLT contact is doubled. Even if hearing loss is found, SLT input is still needed alongside hearing management. The only referral that should be prioritised above the others is audiology — hearing loss must be excluded first because it is the most common and most treatable cause. But SLT referral should happen simultaneously, not sequentially. The NICE guideline NG98 (Hearing Loss in Adults) and the NICE pathway for children's speech and language emphasise that early access to SLT is associated with significantly better long-term language outcomes.

Parent-mediated early intervention for speech delay has the strongest evidence base for children under 3 — multiple RCTs demonstrate that programmes which train parents to modify their communication behaviours (reducing directives, following the child's lead, expanding utterances, using parallel talk and self-talk) are more effective than clinic-based SLT alone for improving language outcomes in pre-schoolers. The reason: children aged 1-3 spend the vast majority of their waking hours with their parents/caregivers, not with SLTs (who typically see them 1 hour per week at most). Changing the quality of every interaction throughout the day — which is what parent-mediated intervention achieves — produces far more learning opportunities than clinic-based therapy alone. The Hanen 'It Takes Two to Talk' programme is the most widely studied parent-mediated intervention in the UK — it involves approximately 8-10 SLT-facilitated group sessions for parents, with in-home video feedback. GPs should be aware that when families are referred to SLT, the most effective intervention may be offered to the parents rather than directly to the child — this should be explained proactively to avoid parental disappointment.

The screen time and speech delay relationship deserves explicit clinical communication because it is actionable and reversible — multiple prospective studies (Chonchaiya 2008, Zimmerman 2007) and a systematic review demonstrate that background television exposure and heavy screen use in under-2s are associated with reduced parent-child verbal interaction (the primary driver of language development), reduced vocabulary at 24 months, and slower language acquisition. The mechanism is displacement: time spent watching screens is time not spent in face-to-face serve-and-return vocal interaction with adults. The AAP (American Academy of Pediatrics) and NHS guidance recommends zero screen time under 18 months (excluding video calls with family members), and maximum 1 hour per day of high-quality, co-viewed, interactive content for ages 2-5 (not background TV). GPs should ask about screen time at every 12-month and 2-year developmental review and provide concrete alternatives: 'For every 30 minutes of screen time, replace it with 30 minutes of reading books together or singing nursery rhymes — this is the single most impactful thing you can do for your child's language development.'

The Bookstart programme (funded by Booktrust, supported by NHS in the UK) is one of the most cost-effective early language interventions available — every family in the UK receives a free Bookstart pack at the 9-12 month health visitor review (containing board books, rhyme cards, and reading guidance) and a second pack at age 3. The evidence: families who receive Bookstart packs show higher rates of shared book reading, and children in Bookstart families have measurably better vocabulary and school readiness at age 5. Health visitors and GPs have the opportunity at the 9-12 month review to: (1) ensure the Bookstart pack was received; (2) demonstrate how to read interactively with a board book; (3) signpost to library Rhyme Time sessions; and (4) emphasise the importance of talking to the baby from birth. The investment of 2 minutes in Bookstart discussion at the 9-month review has downstream effects on literacy, language development, and school readiness.

The age 2 developmental review is the most important speech and language screening opportunity in primary care — it is the standardised contact where delayed language development can be identified and early intervention initiated before school entry. In England, the 2-year check is conducted by health visitors using the Ages and Stages Questionnaire (ASQ-3) and the integrated review combining the NHS 2-year check with the Early Years Foundation Stage 2-year progress check from the child's early years setting (nursery/childminder). GPs who see children at the 2-year routine immunisation visit should use this contact proactively to: (1) ask about language development using the 24-month milestones as a guide (50+ words, 2-word combinations); (2) administer the M-CHAT-R/F if any language or social concern; (3) check tympanic membranes; and (4) refer to SLT and audiology simultaneously if any delay identified. The average age of specialist ASD diagnosis in the UK is 5-6 years — despite families first raising concerns with GPs at 18-24 months. Reducing this diagnostic delay requires proactive GP screening.