The suitability of the DTVP-2 as a measurement instrument for 5 years and 6 months to 5 years and 11 months English-speaking children in South Africa

Abstract

English: As there is limited comprehensive visual perceptual skills test that has been standardised on a representative South African population, occupational therapists in South Africa make use of measurement instruments standardised in other countries to measure children’s visual perceptual skills. A measurement instrument frequently used by SA OTs, the DTVP-2, is a reliable and valid test for the population on which the test was standardised. However, the DTVP-2’s suitability is questioned in a crosscultural setting, specifically the SA population. The aim of the study was to investigate the suitability of the Developmental Test of Visual Perception – 2nd edition (DTVP-2) as a measurement instrument for 5 years and 6 months to 5 years and 11 month English-speaking boys and girls from the City of Tshwane, South Africa. A quantitative, descriptive, observational study was conducted. One-hundred and thirty four (134) study participants were recruited by means of stratified random sampling from English Language of Learning and Teaching schools located within the four educational districts in the urban-suburbs of the City of Tshwane. A selfadministered screening questionnaire was used as a screening method to establish children’s eligibility for inclusion in the study, as well as for parents/caregiver to provide informed consent. Children of parents/caregivers who returned the questionnaires were assessed with the DTVP-2. The DTVP-2’s motor-enhanced subtests were administered according to the prescribed method, while each of the motor-reduced subtests of the DTVP-2 was administered with an adapted method of not implementing the ceiling rule. Results of the study yielded that the SA study sample’s scores differed to the American normative sample. The position in space- and visual closure subtests yielded more accurate results when the ceiling rule was not implemented. It was established that the DTVP-2 was unbiased for gender, with the exception of figureground, when scored according to the prescribed method. The DTVP-2 displayed overall acceptable reliability, however the individual subtests of visual closure, visualmotor speed and form constancy was found to be unreliable. A Rasch analysis revealed that figure-ground and form constancy of the motor-reduced subtests measured a single construct and the four motor-reduced subtests of the DTVP-2 exhibited distorted item difficulty and –linearity resulting in misapplication of the ceiling rule. It is concluded that the DTVP-2 should be used with caution to measure 5 years and 6 months to 5 years and 11 months English-speaking children’s visual perceptual skills and care must be taken when interpreting and conveying scores to parents and other health care professionals. It is recommended that South African occupational therapists adjust and/or be sensitive in their assessment procedures in order to inform evidence-based practice.

Afrikaans: Aangesien daar beperkte omvattende visuele perseptuele vaardigheidsmeetinstrument, wat op ‘n gestandardiseerde verteenwoordigende Suid- Afrikaanse populasie beskikbaar is, maak arbeidsterapeute in Suid-Afrika van meetinstrumente gebruik wat in ander lande gestandaardiseerd is om kinders se visuele perseptuele vaardighede te meet. ‘n Meetinstrument wat dikwels deur Suid- Afrikaanse arbeidsterapeute gebruik word, die DTVP-2, is ‘n betroubare en geldige meetinstrument vir die populasie waarop die toets gestandardiseerd is. Die geskiktheid van die DTVP-2 word egter in ‘n kruis-kulturele omgewing, spesifiek in die Suid-Afrikaanse populasie, bevraagteken. Die doel van die studie was om die geskiktheid van die Developmental Test of Visual Perception – 2nd edition (DTVP-2) as meetinstrument vir 5 jaar en 6 maande tot 5 jaar en 11 maande Engels-sprekende seuns en dogters van die stad van Tshwane, Suid-Afrika te ondersoek. ‘n Kwantitatiewe, beskrywende, obserwerende studieontwerp was gevolg. Een honderd vier en dertig (134) studiedeelnemers is deur middel van ‘n gestratifiseerde steekproeftrekking van uit Engelse taal van leer en onderrigskole, geleë in die vier opvoedkundige distrikte in die stedelike-voorstede van die stad van Tshwane, gewerf. ‘n Self-geadministreerde vraelys was as siftingsmetode gebruik om kinders se moontlikheid vir insluiting in die studie te bepaal, asook vir ouers/versorgers om ingeligte toestemming te gee. Kinders van ouers/versorgers wat die vraelyste teruggestuur het, is met die DTVP-2 ge-evalueer. Die DTVP-2 se motories-verhoogde subtoetse was geadministreer volgens die voorgeskrewe metode, terwyl elkeen van die motories-verlaagde subtoetse geadministreer was deur middel van ‘n aangepasde metode deur nie die plafon-reël te implementeer nie. Resultate van die studie dui daarop dat die Suid-Afrikaanse studie steekproef se tellings verskil van die Amerikaanse normatiewe steekproef. Die posisie in ruimte- en visuele sluiting subtoetse lewer meer akkurate resultate wanneer die plafon-reël nie geïmplementeer word nie. Daar is vasgestel dat die DTVP-2 onbevooroordeeld vir geslag was, met die uitsondering van voorgrond-agtergrond, volgens die voorgeskrewe merk metode. Die DTVP-2 vertoon algehele aanvaarbare betroubaarheid, maar visuele sluiting, visuele-motoriese spoed en vormkonstantheid was onbetroubaar bevind. ‘n Rasch ontleding het getoon dat voorgrond-agtergrond en vormkonstantheid, van die motories-verlaagde subtoetse, 'n enkel eienskap meet en dat al vier die motories-verlaagde subtoetse van die DTVP-2 verwronge item volgorde en –moeilikheidsgraad het met gevolglike wantoepassing van die stop reël. Daar is tot die gevolgtrekking gekom dat die DTVP-2 moet met omsigtigheid gebruik word om 5 jaar en 6 maande tot 5 jaar en 11 maande Engels-sprekende Suid- Afrikaanse kinders se visuele perseptuele vaardighede te meet. Interpretasie- en die oordrag van tellings moet met sorg aan ouers en/of gesondheidsorgverskaffers gedoen word. Daar word aanbeveel dat die Suid-Afrikaanse arbeidsterapeut sensitief is en/of evalueringsmetodes moet aan pas deur bewysgebaseerde praktyk te implementeer.