For example, 30% of respondents from Japan reported testing for C9orf72 variants, despite this gene not contributing significantly to ALS in Japan,19 and 75% of Dutch respondents test for SOD1, which was not significantly different from the rate of testing in non-Dutch respondents (68%; p = 1.0, Fisher exact test), despite published evidence of low prevalence of SOD1 disease-causing variants in the Netherlands.9 Here, C9orf72 is linked to amyotrophic lateral sclerosis.