Blood Test for Life Expectancy: A Useful Decision-making Tool?

Michael van den Heuvel

August 28, 2019

Mortality can be predicted with 14 biochemical markers, according to researchers in the Netherlands.

A team led by Dr Joris Deelen from the department of biomedical data sciences at Leiden University has determined the risk of death precisely within 5 and 10 years.

The biomarkers are different lipids and amino acids. The authors writing in Nature Communications said that better clinical decisions could be made using these markers.

"As gerontologists, we want to determine biological age, because calendar age does not say much about the general state of health for older people," explains co-author Dr Eline Slagboom.

You can have one 70-year-old who is very healthy, while another is already suffering from multiple diseases, she said. "We now have a number of biomarkers available to us with which we can identify at-risk older people and then treat them accordingly."

Many Perspectives, Many Risks

"First of all, it has to be noted that the authors currently do not attest the marketability of applying their risk scores for either research purposes or clinical use," comments Dr Annette Rogge from Germany's Science Media Centre. She is the chairwoman and director of the Clinical Ethics Committee at the University Hospital of Schleswig-Holstein, and acting head of the medical ethics unit at the Institute for Experimental Medicine at the Christian Albrechts University of Kiel.

Dr Deelen and colleagues, however, did discuss how in order to determine whether an elderly patient is too fragile for an invasive operation, it could be significant if he or she belongs to a group with a disease-independent increased risk of dying within the next 5 or even 10 years, adds Dr Rogge.

She points out that many factors play an important role, such as aspects of evidence-based medicine or patient wishes. "To be able to reliably forecast the individual outcome of the patient would be very helpful for the decision," she notes.

"However, the method described provides only one probability that this patient belongs to a group of people who carry a certain risk of dying independent of disease within the next 5 or 10 years." Also, the benefit of the test for prevention is "very abstract", she said.

According to Dr Rogge, there are some dangers:

  • How can we prevent statistical risk assessments from being given too much importance in terms of defining treatment goals?

  • How can we avoid discrimination against patients belonging to statistically-analysed high-risk groups?

  • Who reports this risk and its significance to the patient?

  • How should physicians support patients in dealing with this knowledge?

  • How should physicians safeguard the patient's right not to know?

Dr Rogge concludes: "The use of the biomarker-based test on mortality risks presented here must be evaluated very critically in terms of treatment decisions in individual patients, both for today and as a vision of the future."

Better Choices?

Nonetheless, as Dr Rogge acknowledges, doctors have been wanting to make better choices for many years as to whether an intervention would be worthwhile in older patients. Surgery or chemotherapy is not always the best solution – and also not always in the interest of the patient.

Model organisms such as roundworms or mice have been the focus of research so far in the search for suitable markers of 'biological age'.

Dr Deelen's team worked with blood samples from 44,168 individuals from 12 cohorts (Alpha-Omega cohort, ERF study, FINRISK 1997 cohort, DILGOM study, LLS nonagenarians, LLS Offspring and Partners, PROSPER, Rotterdam study, ALSPAC, EGCUT, KORA F4 and TwinsUK). At the beginning, the participants were 18 to 109 years old.  Of these, a total of 5512 people died during the follow-up from 2.76 to 16.7 years, depending on the study.

Researchers initially identified 159 biomarkers via a standardised platform. Their number decreased to 14 molecules according to biomathematical analyses which were associated with overall mortality, irrespective of other factors.

These include the total lipids in chylomicrons and in very low density lipoprotein (VLDL), the total lipids in high density lipoprotein (HDL), the mean diameter of VLDL particles, the ratio of multiple unsaturated fatty acids to the total amount of fatty acids, glucose, lactate, histidine, isoleucine, leucine, valine, phenylalanine, acetoacetate, albumin, and acetylated glycoproteins.

Strengths and Weaknesses

These biomarkers are involved in various processes such as lipoprotein and fatty acid metabolism, glycolysis, fluid balance and inflammatory processes. "Although many of these have already been connected to mortality in the past, this is the first study that shows their independent effect when combined in a model," the study authors write.

With regard to further strengths, they note the large numbers of study subjects and the established study of metabolites. They do however place constraints, as 14 parameters only "represent a fraction of the metabolism". Nevertheless, Dr Deelen and his colleagues want to integrate their score into ongoing clinical trials to gather more data.

Deelen J, et al: Nat Commun (online) 20th August 2019. 

Translated and adapted from Medscape's German Edition

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