The present study was undertaken among school children from Zimbabwe to validate the culturally modified short form of the Kaufmann MSCA as a screening tool for cognitive impairment. Cognitive development is not routinely assessed in clinical practice due to unavailability of culturally appropriate tools and trained psychometric assessors. Previous validation studies differ on the definition of developmental impairment making direct comparison difficult . When the set cut off point is -1SD, children with both mild to severe impairment are captured, leading to early referral for those with mild impairment .
Researchers concur that a satisfactory screening tool should have both sensitivity and specificity of at least 70% [21, 22]. Previous research emphasizes the importance of the selected cut-off point in assessing the validity of a screening instrument [22, 23]. We compared how the short MSCA was performing at -2SD, -1.5 SD and -1SD below the mean. The sensitivity rates for the MSCA were low (50%, 38% and 17%) compared to the specificity rates which were high (95%, 100% and 100%) when using the more stringent cut-off for the standardized assessment of -2SD. It is plausible that the short form MSCA does not contain enough items to capture the diverse cognitive problems with equivalent precision. A low sensitivity in a developmental screening tool may provide a false assertion to parents and guardians who would otherwise benefit from referral. With such low sensitivity, the universal use of the translated MSCA among Shona speaking children should be applied with caution.
In the context of this study, we found that agreement between the two definitions of cognitive impairment was moderate (using kappa) at -2SD. In clinical practice, it is prudent to link the screening tool to the disease pathophysiology. In the contests of a myriad of biological and environmental factors that potentially negate cognitive development in school children such as infective, environmental, nutritional causes, a simple screening tool will estimate the burden of cognitive impairment and inform policy makers. A study from Pakistan reported prevalence of mild mental retardation among 6–10 year olds of 6.1%  whilst a study from Yemen reported prevalence of 15.7%. A report from a population based survey in Metropolitan Atlanta estimated the prevalence of mental retardation at 10.3 per 1000 in 10-year-old children . It is plausible that the disruption of schools’ educational curriculum that occurred as a result of the economic challenges the country was going through at the time of the study might have indirectly contributed to the high prevalence of cognitive impairment among study participants.
The identification of children with severe cognitive impairment facilitates referral to schools that have a special education curriculum. In developed communities, referred children benefit from individualized cognitive stimulation programmes especially designed to promote student success and achievement. In Zimbabwe although a special education curriculum exists for visual , hearing or cognitive impairment; the classes are congested, are available in private expensive institutions and characterized by a high special education trained teacher shortage . Community based strategies employed elsewhere include integration of children with mild cognitive impairment into normal schools. Detection of intellectual disability is stigmatizing in developing communities . It is essential to guard against stigma by increasing the public awareness of the condition , making screening routinely available to all children at scheduled periods and explaining the benefits of such programs such as the promotion of literacy. Parental compliance with screening protocols is enhanced if stigma is minimised.
In the context of a developing community, screening with MSCA would identify 3/18 7/18 and 9/18 using 2SD 1.5 SD and 1 SD respectively of children with mild to severe impairment who might not have been identified and would serve as an entry point towards a comprehensive primary prevention strategy that seeks to promote early childhood development.
We acknowledge our sample was small compared to the standardization population; however the study generated baseline data on the use of an adapted developmental tool in Shona speaking school children and may supplement existing information on the cognitive development.
When the MSCA validated in South Africa by Ritcher et al., they reported on the predictability validity of MSCA with school achievement and good discrimination between learning disabled children and normal children. We found high positive predictive values (probability that a child who screens positive actually has a cognitive impairment) ranging from 69 to 100%. The negative predictive values reported in this paper support the ability of the tool to discriminate normal children from those with impairment. Since both positive and negative predictive values are impacted by the prevalence of cognitive impairment in the population under study, this may suggests high prevalence of developmental impairment in the sample studied. Population screening may prove to be cost effective for this community.
For most clinicians in resource restricted settings the ability of a tool to over or under refer has a direct bearing on the already stretched resources. The under referral rate was high (proportion of all children who screen negative when they actually have a developmental delay) and ranged from 9 to 15% in this study.
We had the following limitations in this study. A single criterion measure was used. We did not evaluate motor, emotional development, or activities of daily living. We did not administer a supplemental parental or guardian completed screening might have painted a more complete picture. The unavailability of a culturally appropriate developmental instrument to compare as a standard was a limiting factor in this study. Adaptation we made to the short form of MSCA might have influenced the reliability of the test score as some cultural bias in the MSCA might have remained. We did not study the inter-rater reliability using Intra-class Correlation.
From our experience in this study, we learnt that it is possible to adapt components of an established psychometric tool such as MSCA to suit local culture and practice. We were able to conduct a study among children from a general population. The strength of our findings was in the estimation of the prevalence rates of learning disabilities among rural and urban 6–8 year old children after the translation of a commonly used psychometric tool into Shona language.