Summary of Inconsistent Phonological Disorder (IPD), Childhood Apraxia of Speech (CAS) and Core Vocabulary Therapy
This summary is based on Sean Pert’s (2025) article, Speech therapy for inconsistent speech disorder: Let’s try and say this word incorrectly every time!, which draws on a range of published research and clinical guidance relating to the assessment and treatment of Inconsistent Phonological Disorder (IPD).
Pert (2025) explains that IPD is often confused with Childhood Apraxia of Speech (CAS) because both disorders are characterised by inconsistent word production. However, IPD is considerably more common and should be considered before a diagnosis of CAS. Children with IPD produce the same word differently across repeated attempts because they struggle to establish stable word templates and plan sequences of sounds. As a result, traditional articulation therapy and phonological process approaches are often inappropriate.
According to Pert (2025), accurate assessment requires repeated productions of the same words, as single administrations of speech sound assessments may fail to identify inconsistency. He highlights the Diagnostic Evaluation of Articulation and Phonology (DEAP) as an important assessment tool because it includes a formal measure of inconsistency.
Pert (2025) identifies Core Vocabulary Therapy as the most established evidence-based intervention for IPD. The aim is to develop consistent rather than accurate word productions, helping children create stable word forms that support the development of an organised phonological system. Once consistency has been achieved, children can be reassessed and may benefit from more traditional phonological interventions. Pert (2025) also notes that children who do not respond to Core Vocabulary Therapy may require further assessment for CAS and consideration of motor speech interventions.
Reference
Pert, S. (2025, July). Speech therapy for inconsistent speech disorder: Let’s try and say this word incorrectly every time!. LinkedIn. https://www.linkedin.com/pulse/speech-therapy-inconsistent-disorder-lets-try-say-word-dr-sean-pert-mzlze/