Diagnosis, pathology, disease, and symptoms
Is diagnosis decoupled from disease? This is the first question in the analytic framework, and it centres on the possible decoupling of diagnosis from disease. This decoupling can take place if diagnosis is understood to be discerning or learning that results in thorough knowledge. If this is the case, then that which is diagnosed need not be a disease. It can also be the “diagnosis of risk factors” and the “diagnosis of indicators” for a disease. As seen, this first decoupling can also be combined with a decoupling of pathology and disease, and the second question in the framework asks about this second decoupling. If pathology is decoupled from disease, it would mean that a person who has been identified as having a pathology does not necessarily also have a disease. Whether this is the case will depend on, among other things, how the notion of disease is understood.
If the decouplings of diagnosis from disease and pathology from disease are combined and applied to AD discussions, this opens up for a reasoning in which that which is diagnosed can
both be precursors for AD (based on an identified pathology)
and AD. This expanded use of the term “diagnosis” can be contrasted, as Hofmann (
2019, p. 1814) notes, with a narrower use in which the term is used solely for the diagnosis of “manifest disease and suffering”.
In the description of the analytic framework, I stated that the position one takes regarding decouplings between pathology and disease can depend partly on whether one adheres to biological-physiological conceptions or normative conceptions of disease. This can now be explained in some more detail, and applied to the discussion of the NIA-AA’s and the IWG’s conceptualisations of AD.
Biological-physiological conceptions of disease identify a state, ratio or level of an entity or biological/physiological function as statistically normal, and identify deviations from this normalcy as subnormal or abnormal functioning. The notion of disease, in such conceptions, refers to or is identical to the subnormal or abnormal functioning. Christopher Boorse’s oft-quoted conception of disease can be used as an example here (
1977,
2014). For Boorse, diseases are “internal states that interfere with functions in the species design” (
1977, p. 558). Disease is a matter of the subnormal functioning of an organ or some other part of the body, where the term “subnormal functioning” implies that the organ or part of the body functions at a level below that which is statistically normal for the species, in the specific reference group or class (specific to, for example, age or sex). Subnormal functioning is a functioning that is “below the mean of function” in “a typical environment” (Boorse
2014, p. 684).
The conceptualisation of AD as a physio-pathological entity put forward by the NIA-AA squares well with a biological-physiological conception such as that of Boorse, given its focus on abnormal functioning on the molecular level. AD, according to the NIA-AA conceptualisation, refers to specific neuropathological changes, and is “defined” by abnormal levels of the biomarkers pathological tau and Aβ (Jack et al.
2018, pp. 539, 541). The tau biomarker indicates a subnormal functioning of the tau protein.
From within the NIA-AA conceptualisation, that which is diagnosed is AD as the biological construct that refers to neuropathological changes. This construct refers to a certain pathology. This is to couple diagnosis with disease, disease with pathology, and to understand disease along the lines of biological-physiological conceptions of disease. That which is diagnosed in this reasoning is a disease—AD—where AD refers to neuropathological changes. According to the conceptualisation put forward by the NIA-AA in 2018, one cannot have AD without Alzheimer’s pathology, nor Alzheimer’s pathology without AD. However, another decoupling seems to take place: a decoupling between disease and symptoms. Symptoms become an optional extra that one may or may not have when one has been diagnosed with AD.
One more aspect of the biological-physiological conception of disease proposed by Boorse is relevant to my reasoning. Boorse considers diseases to be value-free on a basic level, and states that his conception requires “no value judgement about what forms of human life are admirable or desirable” (
1977, p. 571). He goes on to qualify this statement. While arguing that no value judgement is needed for the diagnosis of disease where the “abnormal”, in the sense of the pathological, has been identified, he acknowledges that evaluative dimensions are present in clinical practice (“Should this disease be treated or not?”). Such evaluation is also manifest when decisions are made about “
therapeutic normality”, as the “absence of a diagnostic abnormality worthy of treatment” (Boorse
2014, p. 685, italics in the original). For Boorse, the evaluation is part of what he terms “disease-plus” conceptions (
2011, p. 28). The evaluative part arises as an addition, typically at the clinic, in order to decide what to do, whether—and if so how—to treat the patient.
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The NIA-AA 2018 suggestion is both similar and different in this regard. On the one hand, according to the terminology used, AD as a disease is not dependent on symptoms that makes it unwanted or undesired. The NIA-AA 2011 suggestion, as aptly noted by Schermer and Richard, “reflects the pathologist’s and [biomedical] researcher’s perspective”, as does Boorse’s theory (Schermer and Richard
2019, p. 141). On the other hand, however, the NIA-AA 2018 framework includes a severity stage-risk table that (while perhaps intended to be descriptive) implies some risk assessment, and risks, after all, are termed “risks” because the eventuality is understood to be negative.
The 2018 NIA-AA framework, in its systems for “staging severity,” includes grades of severity that are based on biomarkers and grades of severity of cognitive impairment (Jack et al.
2018, p. 540). The framework argues for a biological-pathological understanding of AD, but leaves room for the assessment of risks, and risks has connotations of something negative. The evaluative language is also present when the NIA-AA states, for example, that “the risk of short-term cognitive decline increases continuously with worsening (N) biomarkers” (where N stands for neurodegeneration/neuronal injury) (Dubois
2018, p. 542). Risk assessment, arguably, depends on values—that which is assessed is probability of some negative effects or future negative scenario. It can be discussed whether such risk assessments are examples of something akin to Boorse’s “disease-plus” idea. However, something partly different seems to be at stake in the NIA-AA 2018: the severity stages may not be defined in order to assess how to treat the patient, but to provide an independent assessment that helps to specify the severity of someone’s AD for classification purposes.
Further, the NIA-AA recommendations do not give room to a discussion of the role of experiences of possible symptoms—which I will come back to. The discussion omits also the question of whether receiving a diagnosis of AD, as specified by the NIA-AA recommendations, can result in felt harm or suffering. This may occur, for example, if the diagnosis results in severe and persistent worry about AD.
The IWG conception of AD, in contrast, has an evaluative and normative dimension, as have normative conceptions of disease. A normative conception understands disease in relation to human values, needs, and norms, and acknowledges that value judgements are made in the very conceptualisation of disease.
8 Disease, in this understanding, describes a state of affairs that is undesirable, unpleasant, or unwanted—and that calls for action. Various such conceptions exist, such as the conception offered by Lennart Nordenfelt (
1987,
2014). For Nordenfelt, disease is “defined as a state or process that tends to negatively affect its bearer’s health” (
2014, p. 25). Health is understood in holistic terms, as a function of a person’s abilities to achieve her or his vital goals and act intentionally (Nordenfelt
1987,
2014). Health is compatible with the presence of disease, in such a case there arises “the probability” of limitations to one’s agency or negative sensations. If one has a disease, according to Nordenfelt’s conceptualisation, “it is plausible to say that there is a high risk” of having some negative sensations or other negative consequences (Nordenfelt
2014, p. 27).
Further, in a normative conception of disease, symptoms must have negative or probable negative implications for what one can do, or they must be experienced as negative. “Negative” in this context implies, for example, (at least a basic level of) harm, suffering or limited capacities. As Nordenfelt stated: if “there is no risk of suffering or disability at all, it is legitimate to ask what reason there would be for calling the state a disease in the first place” (
2014, p. 27). A normative conception of disease requires at least a probability that symptoms negatively affect one’s abilities to achieve vital goals, and/or that such symptoms are experienced as negative. Symptoms without negative sensations or implications are not sufficient.
The IWG 2010 and 2014 approach, which requires symptoms to be present for a diagnosis of AD to be given, is compatible with this understanding, as also discussed by Schermer and Richard (
2019). Yet, however, it can be questioned whether it is a clear-cut example of a normative conception of disease. As will be unpacked below, the IWG’s way of talking about the diagnosis of preclinical AD opens up for discussions of the meaning of “probable” negative implications, of the threshold of when possible negative implications get to qualify as probable, and whether—if negative implications of preclinical AD cannot justifiably be assessed as probable—the IWG’s conceptualisation of preclinical AD exemplifies normative conceptions of disease. I will take this reasoning in some steps:
The IWG 2010 and 2014 conceptualisation requires that a patient has biomarkers for AD and symptoms, in order for a diagnosis of AD to be reached. Biomarkers alone can show whether someone has Alzheimer’s pathology or not, but this is not sufficient for a diagnosis of AD. As seen, under this IWG conceptualisation, Alzheimer’s pathology refers to biological, pathological changes that “can exist without the concomitant clinical manifestations of AD”, while a diagnosis of AD requires that someone also has clinical symptoms (Dubois et al.
2010, p. 1118). For the IWG, someone can have Alzheimer’s pathology and be at risk for AD, without receiving a diagnosis of AD. Instead, such a person would be diagnosed with preclinical states of AD (see Dubois et al.
2014, p. 620). In this way, “diagnosis” under the IWG conceptualisation may be used when that which is diagnosed is not AD (since AD is repeatedly described as a clinical-biological entity) but preclinical AD, based on Alzheimer’s pathology.
The IWG seems, then, to decouple
diagnosis from
disease and to differentiate between
pathology and
disease.
If symptoms are present, a diagnosis of AD may be reached, in the IWG terminology, but the term “diagnosis” is used not solely to denote the diagnosis of a disease (i.e. one with symptoms). Further, everyone diagnosed with AD has Alzheimer’s pathology, according to the IWG, but not everyone with Alzheimer’s pathology has AD, since (or as long as) AD is considered to be a clinical-biological entity, in contrast to preclinical AD.
9 While the last point is somewhat paradoxical (to be discussed below), the approach taken by the IWG to AD does mean that
symptoms and
disease are kept together. This makes sense, given a normative conception of disease. In such a conceptualisation, a disease is only present if negative effects are experienced or probable.
The IWG emphasises that symptoms do not need to reach a
specific severity for a diagnosis of AD to be made, only that symptoms need to be present. As formulated by the IWG: the diagnosis of AD is “uncoupled from a particular threshold of severity,” and there is “no longer a need to anchor the diagnosis of AD to a dementia syndrome” (Dubois et al.
2010, p. 1120).
10 This opens for different interpretations in relation to normative conceptions of disease.
If it is enough for normative conceptions of disease that the disease probably limits one’s agency or probably brings negative sensations, then a diagnosis of preclinical AD can be understood as exemplifying such a disease conception. However, the inclusion of “probability” (as in “probable negative effects”) brings new difficulties: what percentage of risk is needed to state that preclinical AD will
probably result in negative implications in terms of harm, suffering or limited capacities? This makes the terms “probable” or “risk” central, as can also be seen in Dubois et al.’s discussion (
2016) of AD, when they discuss an “arbitrary dichotomy” between “an already developed AD pathology” and “a situation at risk of AD mainly in asymptomatic individuals” (who exhibit “an isolated brain amyloidopathy […] or tauopathy” (Ibid.).
Here, I contend, it needs to be asked whether preclinical AD can and should be understood as complying with a normative conception of disease if it: (i) is not perceived as a disease (because of the lack of clinical symptoms), and (ii) if “probable negative effects” (in the sense of developing symptoms) may be long delayed or, indeed, never arise because this person dies, for other reasons, before this happens? Further, if one follows the IWG 2010 and 2014 understanding of AD as a clinical-biological entity, then “preclinical AD” is an oxymoron: “preclinical Alzheimer’s disease”, to spell out the abbreviation, does not qualify as a disease. A disease, as defined by the IWG, requires clinical symptoms. A possible way to understand this conundrum is this: if one adheres to a normative disease conception and at the same time wants to acknowledge a preclinical stage of AD, identified on the basis of AD biomarkers only, established terms such as “disease” become slippery. This slipperiness has found its way into the IWG formulations.
Further, given the IWG’s terminology, we can ask about the consequences of being diagnosed with preclinical AD. Does this diagnosis result in patients being more self-aware? Will they interpret memory lapses as subjective symptoms? Research on the lived experience of being at risk for Huntington’s disease (while not knowing whether one has inherited the gene for this disease) has shown that an awareness of the risk can “take over and transform” everyday life. Everyday events, such as dropping a mug or stumbling, are interpreted as symptoms, by some persons (Hagen
2018, p. 78). In the context of the IWG conceptualisation of AD, how would memory lapses be perceived? If they are carefully noted due to the preclinical AD diagnosis and interpreted as very early symptoms of AD by the patient and the doctor, could the very process of diagnosing someone with preclinical AD contribute to this person qualifying for the diagnosis of AD? Whether this occurs may depend on how symptoms are understood and evaluated when determining a diagnosis of AD. (Do they need to be of a certain severity and frequency to qualify as symptoms that are deemed relevant for the diagnosis?). However, even if subjectively experienced memory lapses are not symptoms in the sense required for the diagnosis of AD, the existential dimensions of being diagnosed with preclinical AD must be taken seriously.
The links and decouplings that one makes can be informed by one’s stand in the debate between biological-physiological conceptions and normative conceptions of disease: the links and decouplings may make more or less sense, depending on this stand. However, the links and decoulings can also make more or less sense depending on how one perceives the purpose of a certain conception of disease. For example, if the purpose is to use the conception as a basis in a clinical setting, when diagnosing patients with manifest AD, it can make less sense to decouple symptoms from disease than if the purpose is to use the conception in a research project that seeks to identify AD biomarkers and cluster research participants into different groups based on the presence of different AD biomarkers.
Further, certain decouplings open or close discursive spaces. If it is considered that that which is diagnosed should always be a disease, and if diseases are understood along the lines of the normative conceptions of disease, then it can make more sense to talk about the identification of biomarkers that are characteristic for AD than about the diagnosis of a preclinical disease. If diseases are understood along the lines of biological-physiological conceptions, then it can indeed make sense to diagnose someone with AD based on the identification of biomarkers characteristic for AD. In any case, the choice of decouplings and links between diagnosis and disease, and disease and pathology are not neutral in the light of the way in which the formulation “I have been diagnosed with…” can carry connotations of stability and severity, and function as a powerful social and medical tool (cf. Jutel
2009).
Further, how one understands diagnosis and whether diagnosis is decoupled from disease are also relevant in discussions of overdiagnosis. If overdiagnosis is understood to be “unwarrantedly giving a person the label of disease”, which occurs when “we connect information about an identified entity to disease without knowing whether it will result in manifest disease and suffering” (Hofmann
2019, pp. 1812, 1813), then the analysis also plays out differently in relation to the recommendations of the IWG and the NIA-AA. The risk for overdiagnosis may seem to be high when the NIA-AA conceptualisation is applied. Overdiagnosis typically means that individuals who would otherwise
not have been given a diagnosis of a particular disease because they would never experience any symptoms of the disease are, nevertheless, given this diagnosis. It is difficult to see how this can be avoided with the NIA-AA conceptualisation. On the basis of the IWG 2014’s conceptualisation, in contrast, the NIA-AA conceptualisation can be criticised precisely on the topic of overdiagnosis: from within this IWG conceptualisation, it may be argued, the NIA-AA identifies precursors of AD (where someone is “at risk” for AD), not AD. This means that overdiagnosis will occur in the cases in which Alzheimer’s disease (according to the NIA-AA’s use of the term) that has been detected from the presence of biomarkers does not result in clinical symptoms and manifest disease and suffering.
Screening and diagnosis
What is the relationship between testing for AD biomarkers, screening and the diagnosis of AD under the NIA-AA and the IWG reasoning, and if a certain testing, under a specific disease conceptualisation, constitutes screening, what does that help achieve? This is the sixth question within the framework, applied to these conceptualisations of AD.
The term screening isn’t used in the NIA-AA recommendations, with the exception to Jack et al. (
2018, p. 555), where AD biomarker tests are described as likely to have a “screening role” in the future (see next section). However, through its specific decouplings and linkages, the NIA-AA conceptualisation opens up for a diagnosis of AD to be made very early—years before any symptoms are present. Indeed, one may ask, could anything be earlier than the early testing of AD based on biomarkers and neuropathology, i.e. earlier than a test that some persons take at a stage when they have no symptoms and for this reason do not “necessarily perceive they are at risk” of AD (as in the UK screening formulation)? To say the least: such a testing is a very early testing, and the NIA-AA conceptualisation
opens up for such very early testing. This leads to questions of the role of screening under the conceptualisation of the NIA-AA, as a practice that typically takes place early and targets groups within a population that have no symptoms.
If this very early test is offered to everyone above a certain age, when they visit primary care for other reasons, it is a candidate for the label of opportunistic screening. Or, with another example, if AD biomarker testing is offered to people above a certain age interval who have had no symptoms of AD dementia and take part in research projects on AD biomarkers for other reasons, also this practice may qualify as a case of opportunistic screening (though limited to the participants in the research project). In these cases, and under the NIA-AA conception, a positive test result for AD biomarkers would be the basis for AD diagnosis, and it would not be based on symptoms but offered to people within a certain group who do not perceive themselves at risk, necessarily.
In this way, conceptualisations of AD can open up for early testing practices for AD that qualify as screening, and whether they open up for this partly hinges on decouplings and linkages discussed within the framework: through the decoulings and links that positions early testing of AD based on biomarkers and neuropathology as central to the diagnosis of AD. The development of fast and easy to use AD biomarker tests can help open up for opportunistic AD screening of asymptomatic persons—even if this is not the NIA-AA’s intention.
In the IWG case, Dubois et al. describe a conceptual shift that has led to a “disease model that begins with risk factor assessment (directed at the potential for primary prevention), advances to screening (for early detection and early intervention of disease—secondary prevention), and leads to treatments and monitoring of treatment effects” (Dubois et al.
2016, p. 294). This approach, they add, includes “screening with tests with high sensitivity, lower specificity, and low costs, to those with higher specificity and value with potential for longitudinal quantification” (ibid). The IWG does not discuss screening any further, and two interpretations are possible. Either screening is temporally inserted between the diagnosis of preclinical AD and the diagnosis of clinical AD, as a screening for early symptoms of clinical AD; or (arguably a more stretched interpretation) that AD biomarkers are screened for, which makes screening for preclinical AD (where screening could mean that a biomarker test is offered to a part of a population who do not perceive themselves as affected by AD) that which result in the diagnosis of preclinical AD (where this diagnosis is given based on the result of the same biomarker test).
Irrespective of when screening takes place under the IWG reasoning, the conceptualisations of AD, in the IWG and in the NIA-AA, have implications for how to understand the temporal relationship between screening, testing for AD biomarkers and the diagnosis of AD. Further, much screening ethics have examined population-based screening practices. National committees that assess such screening practices including ethical aspects of them are established in many countries, while ethical guidelines for opportunistic screening are much more rare. If some AD conceptualisations encourages practices of early testing for AD, which may then be performed in ways that qualify as opportunistic screening, then it is high time that ethical guidelines also for opportunistic screening practices are developed—akin to those applied to population-based screening practices.
Spaces of possibilities and other implications
Question seven and eight require reflection about what the decouplings and linkages makes possible, together. They ask how the decouplings or linkages can help enact some “spaces of possibilities” (Hacking
1985, p. 165) more than others, and what the decouplings or linkages can help achieve, more broadly, for people as individuals, for society, for our understanding of human life, and for clinics.
What spaces of possibilities do the NIA-AA and the IWG make possible? As already discussed, the decouplings and linkages of the NIA-AA help to enact spaces of possibilities in which the detection of biomarkers can be given priority. This becomes particularly possible thanks to the specific linkage of pathology and disease and the decoupling of disease and symptoms in the NIA-AA’s recommendations. If the NIA-AA conceptualisation were to become the conceptualisation that is used in research and at clinics, and if clinics were to align their work with these recommended conceptualisations and categories of different stages of AD, this would help to give priority to biomarkers, and put preclinical AD into a category of its own. This is also a possible outcome if the IWG conceptualisation were to become the established conceptualisation, even though the IWG’s focus on a dual clinical-biological understanding of AD leads to a less intense focus on biomarkers. From within the IWG conceptualisation, the enacted spaces of possibilities include spaces in which symptoms are still regarded as central to the diagnosis of AD (though not to that of preclinical AD).
It is important to note, as shown by Boenink, that the NIA-AA’s guideline can function both as “gatekeepers and trailblazers” (
2017, p. 224). The NIA-AA has been cautious towards the introduction of AD biomarkers tests into clinical practice, yet their guidelines “can create a world which is prepared to include certain technologies in the future, even while advising against introducing the same technologies into current clinical practice” (Boenink
2017, p. 225). The NIA-AA does discuss AD biomarkers as part of future practices, as when stating that “in the future, less-invasive/less-expensive blood-based biomarker tests along with genetics, clinical, and demographic information will likely play an important screening role in selecting individuals for more-expensive/more-invasive biomarker testing” (Jack et al.
2018, p. 555). In this way, and as put by Boenink, “these guidelines pave the way for a smooth introduction of biomarker tests later on. They act as trailblazers, even when they are also gatekeepers” (
2017, p. 224).
If preclinical AD is made a category of its own, this have specific effects. For example, both the NIA-AA and the IWG use the term “preclinical AD” and suggest that preclinical AD can be diagnosed based on biomarkers only. Such a recommendation for a diagnostic procedure mobilise biomarkers as central in the discourse, and as offering conditions for the phenomenon that Hacking termed the “make up” of new people (Hacking
1985). New conceptualisations and categories, Hacking argued, could help to enact new “spaces of possibilities”, people can be placed into new categories, understand themselves in new ways through them, mobilise themselves into new social groups, and help to modify the initial categories (Hacking
1985, p. 165). In the present discussion, new categories of people, such as those with preclinical AD, come to exist, which can feed into the ways people make use of and understand AD conceptualizations. The new categorisation can affect behaviour, such as calls for AD biomarker testing and further follow-ups. At stake, to use Hacking’s formulation, are “looping effects”: new categories, new “modes of description come into being, new possibilities for action come into being in consequence” (
1985, p. 166).
With the availability of categories of preclinical AD, more people can come to ask for tests for preclinical AD, use this category as part of their self-understanding, which can further promote calls for such testing—and promote a shift in the understanding of AD towards an understanding that sees preclinical AD as a disease for which treatment should be developed and given. Indeed, the availability of biomarker-based diagnosis for AD has already helped to create a new category of people: people with preclinical AD (see, for example, the Waters’ Biomedical Website which asks “Do you have Preclinical Alzheimer's Disease?”, followed by the statement: “47 Million of us [in the USA] do!” (Waters
2018).
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Conceptualisations of preclinical AD and the looping effects can also contribute to a
pathologising and a
diseasisation of human life. A pathologising of human life occurs if it comes to be perceived as normal that people are identified as having a pathology before they have any symptoms. A pathologising of human life can be understood as part of a larger tendency of biomedicalisation. As suggested by Clarke et al. (
2003, p. 162), biomedicalisation refers to “the increasingly complex, multisited, multidirectional processes of medicalisation that today are being both extended and reconstituted through the emergence of social forms and practices of a highly and increasingly technoscientific biomedicine.” Clarke and colleagues suggest that, in contrast to medicalisation and its focus on “control over medical phenomena” that were previously not seen as medical, biomedicalisation practices “emphasize
transformations of such medical phenomena and of bodies, largely through sooner-than-later technoscientific interventions” (Clarke et al.
2010, p. 2).
The IWG’s understanding of preclinical AD—through its decoupling of diagnosis from disease and differentiation between pathology and disease—may open up for such a pathologising, without this being the intention of the IWG. Under the IWG, it is possible to be identified as having a pathology before one has any symptoms. In this way, the new conceptualisations of AD underscore concerns over biomedicalisation. If the category of preclinical AD becomes established, parts of life that have not been perceived as falling within the domain of medicine can start to do so.
Further, however, if the NIA-AA conceptualisation and categories come to be used, it will not be necessary to manifest clinical symptoms of AD to be given a diagnosis of AD—and this can help transform people’s understanding of the role of symptoms for disease, though a technoscientific process of biomarker-based diagnosis. Symptoms, following the NIA-AA, are not needed for the diagnosis of AD. Indeed, because the NIA-AA holds together pathology and disease, more is at stake than a pathologisation in which having pathologies—at a genetic, molecular, or cellular level—may become normal. The NIA-AA conceptualisation, if accepted, may lead to what can be called a
diseasisation, in which preclinical non-symptomatic conditions are understood to be diseases. Given the NIA-AA’s vocabulary, if I test myself for AD biomarkers, I will not only learn about underlying pathology that may or may not manifest in symptoms: I will learn that I have, already, the disease of AD.
12 This, then, is different from the already common situation where someone takes pills in order to minimize the risk for a disease (as when someone takes a drug to decrease blood pressure, as a preventive measure, to lower the risk for a heart attack). Such a shift in conceptualisation, and the diseasisation, is of no small consequence: it can become a powerful tool for people diagnosed with preclinical AD to put pressure on different social and medical actors to prioritize the development of treatment and for proponents of technoscientific interventions of AD to put pressure on politicians to fund more research for the development of drugs or other interventions—arguing that they have now been diagnosed with this disease. Such development can of course be beneficial and central to future treatments of AD, and I am by no means arguing against the value of such treatment. However, the new conceptualisations can also contribute to a shift in shared understandings of what it means to have a disease, and to a diseasisation of human existence where to be diagnosed with diseases without having any symptoms comes to be perceived as a responsible way of acting, by patients and doctors. This can also help open up for screening practices: in such a future scenario, to screen for preclinical AD might be one route to a later diagnosis of preclinical AD. Indeed, a number of trials are already on-going with the aim of developing tests for AD biomarkers in blood samples, and such blood-based “screening biomarkers for AD can meet the scalability needs required for primary care settings and even for the broad population-based screening approach that may evolve with the advancing innovative precision medicine framework”, suggests Hampel et al. (
2018, p. 641).
Possible implications of the category of preclinical AD, should it become established, has been discussed also elsewhere (cf. Boenink
2017). The analytic framework, however, helps clarify how implications such as that which I have labelled as diseasisation hang together with specific decouplings and linkages between—in this case—pathology and disease.
Further, the current situation in which there is no cure and only modest treatment for AD sharpens ethical concerns if or when preclinical AD were to become an established category. Such an establishment could help create an existentially-temporally condensed situation in which patients, when diagnosed with preclinical AD, are made to consider their possible future(s), should the preclinical AD develop into AD dementia—and make sense of the uncertainties involved (since not everyone with preclinical AD develops AD dementia). If the NIA-AA conceptualisation becomes the established one, we must ask how we are to live with the implications of diseasisation, should one’s biomarker test be positive. For healthcare professionals, the choice of whether to offer detection of AD biomarkers when no cure and little treatment for AD is available is intertwined with the question of what existential issues and decisions healthcare systems help to make central for patients and potential patients. The support available for those who test positive is also a consideration, though not a new challenge. What is partly new in dementia settings, however, and a question to address for healthcare professionals who offer biomarker testing, is whether their way of talking about, framing and explaining such testing contributes to diseasisation, and whether this should be seen as troubling or not—for patients, the healthcare system, and society.