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APOE ɛ4 Allele Testing and Risk of Alzheimer Disease

Author/s: 
Choudhury, Parichita, Boeve, Bradley F., Ramanan, Vijay K

A 64-year-old man presented with concern about an abnormal genetic test result for apolipoprotein E (APOE) obtained through his primary care physician. He reported forgetfulness and word-finding difficulties for 3 years but performed all activities of daily living independently and was generally healthy. His father and maternal great aunt developed dementia in their 70s. Physical (including neurologic) examination, basic laboratory studies, and brain magnetic resonance imaging results were normal. The Short Test of Mental Status (STMS) score was 33 (maximal attainable score of 38 indicates best performance). Neuropsychological assessment showed average to above-average performance in all cognitive domains, accounting for age and education. Results of his genetic testing for APOE were reported as follows: “This individual possesses an apolipoprotein E genotype (3 and 4) that indicates, with high specificity, that Alzheimer’s disease is the cause of or a contributor to the observed dementia.

Keywords 
dementia Alzheimer Disease Genetic testing

Consistency of Direct to Consumer Genetic Testing Results Among Identical Twins

Author/s: 
Huml, A.M., Sullivan C., Figueroa, M., Scott, K., Sehgal, A.R.

Abstract

Purpose

To evaluate the consistency of 3 commonly used direct to consumer genetic testing kits.

Background

Genetic testing kits are widely marketed by several companies but the consistency of their results is unclear. Since identical twins share the same DNA, their genetic testing results should provide insight into test consistency.

Methods

42 identical twins (21 pairs) provided samples for three testing companies. Outcomes were concordance of ancestry results when i) twin pairs were tested by the same company and ii) the same participant was tested by different companies. Concordance of 8 self-reported traits with 23andMe genetic analyses were also examined.

Results

Concordance of ancestry results when twin pairs were tested by the same company was high, with mean percent agreement ranging from 94.5%–99.2%. Concordance of ancestry results when participants were tested by two different companies was lower, with mean percent agreement ranging from 52.7%–84.1%. Concordance of trait results was variable, ranging from 34.1% for deep sleep and detached earlobes to 90.2% for cleft chin.

Conclusion

The consistency of consumer genetic testing is high for ancestry results within companies but lower and more variable for ancestry results across companies and for specific traits. These results raise questions about the usefulness of such testing.

Keywords 
consistency Genetic testing identical twins
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