Sickle Cell Neurocognitive Screening Measures May Have Inherent Educational Bias

Stéphanie Forté, MD, MSc

Findings from a new study suggest there may be inherent educational biases in neurocognitive screening measures of adult patients with sickle cell disease.

The study, presented at the American Society of Hematology (ASH) 2020 Annual Meeting by Stéphanie Forté, MD, MSc, Department of Medicine, University Health Network, Canada, reported on the prevalence of suspected cognitive impairment in a sickle cell population using the Rowland Universal Dementia Assessment Scale (RUDAS) and Montreal Cognitive Assessment (MoCA).

The investigators also examined the presence of educational bias so that mitigation strategies may developed.

The Importance and Limitations of Neurocognitive Screening Tests

This year, ASH released strong recommendations that clinicians assess their sickle cell disease patients for cognitive impairment using simplified sampling questions.

"Cognitive impairment is a dreaded complication of sickle cell disease that impacts quality of life, school performance and employment," the investigators wrote.

Nonetheless, there yet remains guidance on which screening strategy is optimal. Furthermore, as noted by the investigators, several screening measurements are biased by language and education.

The Study: Methods and Screening

In this cross-sectional study, Forté and colleagues enrolled patients (n = 45) from the MGRR out-patient clinic at Henri Mondor Hospital, Créteil, France. All patients were ≥18 years old (median age, 39 years old) and represented all sickle cell disease phenotypes.

The investigators performed cognitive screening using the RUDAS, MoCA, as well as an additional visuospatial task that involved copying overlapping triangles.

Using criteria from previous studies, they considered RUDAS and MoCA scores <28 and <26, respectively, to be suggestive of cognitive impairment. Such patients were then to referred for definite neurophsychological evaluation.

Additionally, all participants completed surveys on demographics and screenings for depression and anxiety (using the Hospital Anxiety Depression Scale [HADS]).

The investigators then scored educational attainment according to the number of years of schooling for the highest completed diploma.

A linear regression was performed to identify any potential associations between RUDAS, MoCA, and social determinants of health.

The Findings: Assessing Educational Bias

Of the patients evaluated, 33 had RUDAS and 29 had MoCA scores that were suggestive of mild cognitive impairment. Furthermore, the investigators found a strong correlation between both tests (r = 0.48; P = .001).

The team noted that test scores increased significantly with increasing level of education (For RUDAS, r = 0.48 P = .015; For MoCA, r = 0.39; P = .007). 

However, there was no association between the tests and HADS score.

“RUDAS and MoCA test items most biased by education were visuoconstructional tasks,” Forté and colleagues wrote. “Tasks assessing executive functioning and language were also biased in MoCA.”

They observed that educational bias was reduced when the 3D visuospatial task of the RUDAS was substituted with a 2D task.

A proposed mitigation strategy was adding 1 point if the participant had ≤12 years of education following kindergarten. The mitigation effect was significant in the RUDAS (r = 0.13; P = 0.131) but was only partially observed in the MoCA (r = 0.30, P = 0.047).

“Overall, these results suggest there is an educational bias in the neurocognitive screening of adult sickle cell disease patients using available tools such as the RUDAS and MoCA,” the investigators concluded. “Although RUDAS was less biased overall, visuospatial assessment remained biased.”

Nonetheless, they acknowledged that prospective validation is ongoing.

The study, “Evidence of Educational Bias in Cognitive Screening of Adults with Sickle Cell Disease: Comparison of Available Tools and Possible Strategies for Mitigation,” was presented at ASH 2020.