Reliability and validity of the Portage assessment scale for clinical studies of mentally handicapped populations

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Abstract
The Finnish version of the Portage Assessment Scale was used with 114 aspartylglucosaminuria (AGU) persons aged between 1 and 56 years. Ninety-three persons with AGU were also given psychological tests, mainly SB (Finnish), WISC-R and WPPSI, but also Merrill-Palmer, Bayley, Leiter and WAIS tests. The data also include for the reliability assessment a sample of 30 normal pre-school children. The internal consistency reliability was calculated for the areas of socialization 0.80, language 0.81, self-help 0.73, cognitive 0.70, motor 0.75 and for the whole scale 0.80. The factor analysis produced one very strong factor. The results of the Portage assessment were compared to the developmental levels provided by the tests. Both methods gave almost identical cross-sectional descriptions of the skills of patients with AGU, which was interpreted as providing a cross-validation for Portage in clinical use and to mean that Portage can be used as a reasonable assessment method. The advantages of Portage include easy use by non-psychologists, concrete descriptions of the skills, the 5 areas, and the close relation to rehabilitation.