“The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening for cognitive impairment in older adults.” (link)
Blunt questions: Is screening in this arena just futile, given the same expert conclusion twice in this decade? Is screening even worthy of more investigation? And why bother in the first place? After all, current practice is able to identify millions of patients without a consensus screen or designated diagnostic pathway. Why not focus on a different approach and service issues? Perhaps cognitive impairments don’t fit disease paradigms that find screening useful.
Reviewing the results from over 80,000 subjects, in dozens of studies, using 49 different screening instruments, done by hundreds of investigators, the US Preventive Services Task Force expert panel updated their findings from six years ago: despite all the work, there is not enough good data to recommend a valid way to screen older folks for cognitive problems. Furthermore, they state (to paraphrase) that current interventions may not make much of a difference anyway. [The same group does find enough evidence to make pronouncements about screening for various cancers].
This isn’t surprising news, of course. The panel does describe current practice: to pursue diagnosis when symptoms arise. In the accompanying editorial, those authors also acknowledge that there is no disease-modifying therapy to be had. In other words, medications like donepezil and memantine are interventions that might help some symptoms, but the condition will progress anyway. And a recent BMJ review finds that those meds used off-label aren’t that helpful in mild cognitive impairment.
The theory of screening is to catch something early to do something about it. So what would be the point of cognitive screening, even if we had a good screening tool? We have newborn screening for metabolic diseases, screening for breast cancer, and depression screening in primary care, each of which have proven medical interventions. But screening is complicated: the noble idea of infant cancer screening for neuroblastoma failed in Canada, Germany and Japan, may have led to some unnecessary surgeries and harms, and made no difference in mortality, therefore screening was discontinued.
CMS (Medicare) wants clinicians to consider dementia by direct observation and history, and to use a screening instrument if appropriate [CMS does want documentation of Activities of Daily Living, too, which can be affected by dementia]. So why not “screen” by asking the single question: “Are you worried about your memory or how you function, or are other people worried about you?” [aka “subjective cognitive complaints” by some]. If yes, the usual primary care pathway is then straightforward: refer to a friendly local geriatrician, neuropsychologist, neurologist or psychiatrist, which ever seems best for the patient, and let them do the diagnostic workup.
The editorial, by Peterson (Mayo) and Yaffe (UCSF) mentions the “inevitable availability” of biomarkers to screen or diagnose various dementias. Yes, the prodigious NIA-AA Research Framework might be able to do away with cognitive tests, to redefine dementia based on imaging, blood or CSF biomarkers. Yet the Mayo group reported that the performance of biomarkers in a cohort from Olmstead county was marginal: the study “resulted in a small but statistically significant improvement in predicting memory decline over a model with more readily available clinical and genetic variables. The clinical importance of this difference is uncertain.”
Peterson and Yaffe seem to miss the point that the USPSTF review is about screening, and blur screening with diagnostic testing. They state that concerned patients and families might be helped by knowing about specific problems, or conversely reassured if the problems cannot be confirmed. That sounds like they are discussing sophisticated and validated neuropsychological tests, not primary care brief screening tools, which may have a positive predictive value as low as 20% from age 65-74 (USPSTF Table).
Biomarker model studies are usually correlated with cognitive testing data, anyway, for validation. Although the editorial discusses the problems of under-diagnosis in general, the authors don’t take the opportunity to discuss possible improvements while we wait on biomarkers. The authors don’t take the opportunity to discuss issues with over-diagnosis or mis-diagnosis. One might also ask: does a “delay in diagnosis” really make any substantial difference to the patient or to the course of the disease?
They then state: “The absence of evidence for benefit [the USPSTF report] may lead to inaction….It would be a mistake if clinicians did not consider the value of screening for cognitive impairment on a case-by-case basis.” The USPSTF recommendation does not extol inaction, it’s assessing how good the current screening tools are, since not all screening is of medical value: urinalysis in healthy kids, annual ECGs, or commercial CT scanning for various ailments.
Is there a bigger picture point? Well, basically, how can we help folks who are having cognitive issues, or worried about that problem? Dementias are real, and the concern is real. The Task Force implies that the cognitive screening literature is just too untidy. They enumerate a lot of issues: lack of consensus definitions in studies, lack of consistency in outcome measures, and the need for better assessments of the impacts of the process on patients, caregivers, families and society. These aren’t likely to improve without applied leadership, so why pursue more studies?
As for interventions, one does not even need a screen to educate every age 65+ patient about the WHO Dementia Risk Reduction guidelines, even if asymptomatic. Wouldn’t that be a better service model? For symptom management, along with a referral for diagnosis, how about a referral to “palliative care,” as described in the Lancet Commissions review of dementia? In Canada, that might be a referral to a “primary care memory clinic.” The UK has a similar concept for dementia care and pathways, in some places. [BTW, the Lancet review does not recommend cognitive screening, but some “innovative” UK GPs use various screening instruments, valid or not, as described in that last link].
As far as one knows, there isn’t a screening instrument for happiness, life satisfaction, or love. So the screening paradigm may not applicable to everything. In a positive world, of course, there’s no need to intervene. Screening is for poorly detected negative things, to help one decide on an intervention. But does one need a screen to detect unhappiness, life dissatisfaction, or a lack of love, before taking action? So, screening issues aside, let’s go get some disease-modifying therapy already!