Early detection of Alzheimer's disease (AD) is a primary objective in order to develop strategies to mitigate or reduce the clinical burden of the disease. For this early detection to be effective, specific biomarkers are required to identify individuals who may develop the disease as early as possible. Until now, the biomarkers most commonly used in clinical practice to aid diagnosis have been obtained primarily from the cerebrospinal fluid of those with the disease. In recent years, however, the focus has shifted to biomarkers that can be of equivalent diagnostic value and that are easier to obtain without losing any information. To this end, the presence in blood of various molecules that appear to be useful for diagnosing AD is being studied.

The work of Palmqvist and colleagues builds on this type of study and focuses on identifying a biomarker in blood, a phosphorylated form at position 217 of the Tau protein, as sufficient for the diagnosis of AD. This same form of modified tau protein has been proposed before as an important biomarker in AD. What makes this study particularly relevant? For one thing, it combines populations from Sweden, Italy and Spain, which is often necessary to be able to establish to what extent the findings can be extrapolated to other groups. And, more importantly, because the analysis does not only focus on individuals studied in tertiary clinical services, but also includes individuals followed in primary care. In the latter group, the results are also in the same direction as in the case of more specialised services, although they are somewhat lower, but this may be related to less disease progression in these individuals.

On the other hand, another interesting feature of the study is the use of an automated system that would allow population screening on a larger scale and implementable in the various participating hospitals. That said, the system is not as effective as others, with higher operational costs, currently in use, albeit less widely.

Finally, it should be noted that some of the authors of the paper report that they have obtained funding or participated in conferences funded, in part, by the manufacturer of the automated equipment used in the study.

This is a very well conducted study, of high scientific quality and which studies the performance of the plasma marker p-tau217 in primary and secondary care settings, using an automated platform that is already present in many centres (Lumipulse).

The usefulness of this technique has already been explored in various clinical populations in reference units (both in Spain and abroad, including our recently published series). What this article contributes is the simultaneous study of several cohorts from different centres and the inclusion of a Primary Care cohort. The results are very good, even in these more demanding scenarios, using a two-point cut-off approach that classifies patients as high (positive), low (negative) and intermediate (borderline).

The results point to the clinical usefulness of this marker and the capacity to extend its use from specialised consultations (where it is beginning to be used, and is already recommended by the SEN Dementia Group) to less specialised consultations. This will contribute to ‘democratising’ the precision biological diagnosis of Alzheimer's disease, avoiding in many cases the need for more invasive (lumbar puncture) or expensive and less available (PET) marker determinations.