In their editorial “Sharpen That Needle,”1 Herskovits and Growdon argue that the diagnostic criteria for Alzheimer disease (AD) should be redefined to incorporate lumbar punctures. I disagree with them regarding the incorporation of invasive tests when it does not affect the clinical management of AD. Without cost or risk to the patient, the sensitivity of the National Institute of Neurological and Communicative Disorders and Stroke–Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria compares favorably with the cerebrospinal fluid (CSF) β-amyloid (Aβ) and tau protein measurements (65%-96% vs 75%-100%). The specificity is also reasonable at around 70%.2,3 Although a singular study cited an extremely low specificity of 23% for the NINCDS-ADRDA criteria4; this was only seen when trying to differentiate early-onset AD (age <65 years) from the frontotemporal dementias. These rare dementias typically have a faster progression, tell-tale examination findings, and, most importantly, similar management as AD.
Kuhlmann D. Primum non nocere. Arch Neurol. 2011;68(3):395-399. doi:10.1001/archneurol.2011.15