Missing scores cannot make a memory-concern question detect most low processing-speed performers

Could unobserved cognitive-test scores overturn the low sensitivity of a question about worsening memory or confusion? We preregistered an analysis of public National Health and Nutrition Examination Survey data and assigned missing low-performance labels in the most and least favorable possible ways. Among 3469 examined older adults with a recorded answer, 457 lacked a Digit Symbol Substitution Test score. Observed-score sensitivity was 24.15%. Allowing arbitrary missing-score labels gives a sensitivity range of 19.27% to 33.78%; the upper endpoint has a confidence interval from 30.75% to 36.82%. Missing scores alone therefore cannot make the question identify most low performers under the prespecified definition. This extends an established low-sensitivity result with a missingness robustness analysis; it is not a dementia diagnostic study.