Validation and standardization of the Psycholinguistic Assessments of Language Processing in Aphasia (PALPA)

ABSTRACT

Aims

This study aimed to standardize and assess the psychometric properties of a selected protocol of subtests from the Psycholinguistic Assessments of Language Processing in Aphasia (PALPA), a battery of tests that measures a wide range of language abilities underpinned by a cognitive neuropsychological model of language processing.

Methods

One hundred healthy participants were recruited (mean age 64 ± 10.4 years) as part of a large population-based study assessing cognitive change in Amyotrophic Lateral Sclerosis (ALS) and were assessed using the PALPA protocol. Reliability was measured by means of internal consistency and test-retest reliability. Validity was assessed through an inter-correlational analysis between PALPA subtests and a correlational analysis between PALPA subtests and external variables. A supplementary validation study (n = 35) of the Auditory Sentence – Picture Matching subtest of the PALPA against the TROG-2, another test of grammatical and syntactic processing, was carried out.

Results

The PALPA protocol had good internal consistency (Cronbach’s alpha coefficient = 0.78). Intra-class correlations indicated moderate to excellent test-retest reliability (ICCs ranging from 0.62 to 0.93), with significant agreements (p <.05) between time points in most cases. Validity of PALPA subtests was demonstrated by significant positive correlations among PALPA subtests (especially between those measuring the same language construct, ranging from 0.41 to 0.74). Moreover, the PALPA subtests correlated equivalently with external variables such as age, years of education and IQ, which further supported construct validity.

Conclusion

This study has proven adequate reliability and validity of a standardized protocol of the PALPA. Based on results from the assessment of psychometric properties of the PALPA protocol studied, adjusted IQ-based PALPA scores were generated.

KEYWORDS:

• Neuropsychology
• language
• PALPA
• psychometric properties
• standardization

Supplementary material

Supplemental data for this article can be accessed here.

Acknowledgments

We are grateful to Professor Max Coltheart for his kind interest in our use of the PALPA and for allowing the reproduction of the PALPA model.

Disclosure statement

This article is based on the dissertation completed by Pinto-Grau (2020).

Dr Marta Pinto-Grau, Ms Sarah O’Connor, Ms Lisa Murphy, Mr Emmet Costello, Mr Mark Heverin and Dr Alice Vajda have nothing to disclose. Professor Niall Pender serves as Associate Editor of the International Journal of Neuroscience. Professor Orla Hardiman serves as Editor-in-Chief of the Journal Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration.

Author contributions

MPG contributed to the process of data collection, data scoring, data entry, analysed the data and wrote the manuscript; SOC, LM and EC contributed to the process of data collection, data scoring and revised the intellectual content of the manuscript; MH and AV administered the management aspects and revised the intellectual content of the manuscript; NP and OH supervised all clinical and neuropsychological aspects of the study and revised the intellectual content of the manuscript.

Additional information

Funding

This research has received funding from The Motor Neurone Disease Association (MNDA) in the UK (Grant ref. number Hardiman 879-792).