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Assessment of nutritional status: what does it mean?

Cynober, Luca,b

Current Opinion in Clinical Nutrition & Metabolic Care: September 2018 - Volume 21 - Issue 5 - p 319–320
doi: 10.1097/MCO.0000000000000501
ASSESSMENT OF NUTRITIONAL AND METABOLIC STATUS: Edited by Dwight E. Matthews and Kristina Norman
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aClinical Chemistry Department, Cochin Hospital, AP-HP

bLaboratory of Biological Nutrition, EA4466, Faculty of Pharmacy, Paris Descartes University, Paris, France

Correspondence to Prof. Luc Cynober, Clinical Chemistry Department, Cochin Hospital, AP-HP; Laboratory of Biological Nutrition, EA4466, Faculty of Pharmacy, Paris Descartes University, Paris, France. E-mail: luc.cynober@aphp.fr

Modern clinical nutrition emerged at the end of the Second World War, that is more than 70 years ago. However, desperately, we are still discussing how to define malnutrition (undernutrition) [1,2,3▪] and what is the best way to assess it [1,2,3▪]. Clearly, failure to define the former has left few chances to accurately define the latter.

In addition, the exploration of nutritional status does not pose a single question but several ones which require different tools. The different questions that I have identified are the following:

  1. Is a given patient at risk of malnutrition? It is just a risk but it is important to answer this question because prevention is certainly the most cost-effective action. There are a great many factors which pose a risk of malnutrition: environmental, psychological, physiological or pathological. Nevertheless, a risk is just a risk. For example, an elderly person who is losing his/her spouse after 60 years of married life will be depressed, will eat less, will lose weight, and will be malnourished. However, there are exceptions (as described in the book ‘Die unwürdige Greisin’ by Berthold Brecht).
  2. Next, when preventive action failed or did not take place, the question is as follows: Is the patient malnourished and what is the severity? For the diagnosis, please return to the beginning of this editorial, for the severity; a decrease in BMI is far from perfect [4▪], but it makes sense to believe that the lower the BMI, the more severe the state of malnutrition. Transthyretin (formerly called prealbumin) is certainly pertinent providing that C-reactive Protein (CRP) (i.e. to assess inflammation) is measured in parallel [5▪]. Importantly, a number of questionnaires (Mini nutritional assessment test, NRS 2002, subjective global assessment (SGA), patient-generated SGA) mix items which assess the risk of malnutrition and the severity of malnutrition [6▪].
  3. Malnutrition leads to complications. That is a fact. Therefore, a forthcoming question is ‘how to evaluate the risk of complications associated with malnutrition?’ The nutritional risk index (NRI) and the geriatric NRI have been designed for this purpose. Currently, the NRI is very often used as a marker of malnutrition, but to the best of my knowledge, no article has validated the NRI in this setting. In fact, the term ‘nutritional risk’, which is very frequently used, is totally confusing because we do not know whether this term refers to the risk of malnutrition or to the risk of complication associated with malnutrition. The majority of patients undergoing large digestive surgery become malnourished, but hopefully only a minority develop severe complications. Therefore, the term ‘nutritional risk’ must be prohibited.
  4. We have malnourished patients evidently at risk of complication. The arising question is how to select the patients who would benefit most from renutrition? Tools have been designed to answer this question (i.e. Malnutrition Universal Screening Tool, Nutrition Risk in Intensive Care (NUTRIC) [7▪]) and should certainly be used more frequently in a medicoeconomic context.
  5. The efficacy of any therapy must be assessed and the renutrition of malnutrition should be no exception to this rule, in particular because we have many therapeutic options in the field of nutrition of which the choice, beside efficacy, is conditioned by the iatrogenicity, the compliancy and the cost. To be pertinent, a parameter suitable to assess the efficacy of renutrition must be very sensitive. The most sensitive parameters are plasma proteins with short half-life such as transthyretin and retinol binding protein providing a simultaneous measurement of CRP [5▪].

To interrogate these various questions and items in pursuit of an answer is, in my opinion, the key issue. In fact, a number of articles are still comparing various items (parameters and or questionnaires). These articles attempt to describe the prevalence of malnutrition in a given population, yet they are never able to achieve any reliable conclusion due to the varying prevalence of malnutrition according to the parameters, and simply because the different items under study explore different things.

There are three difficulties that require improvement in this field:

  1. to have an established gold standard which permits an answer to each specific question formulated above.
  2. it is extremely difficult to have a pure marker because patients who display nutrition-related complications are among those who are malnourished, and the latter were obviously at risk of malnutrition before becoming malnourished. This is why the mini nutritional assessment, which basically indicates the risk of malnutrition and its severity, has been found to be an independent predictor of the risk of mortality [8▪].
  3. Investigators should think to what they are doing. For example, BMI is sometimes used longitudinally. This is meaningless because height has very little (no) chance of changing over a 1 or 2-month observation period!
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Acknowledgements

None.

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Financial support and sponsorship

None.

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Conflicts of interest

There are no conflicts of interest.

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REFERENCES AND RECOMMENDED READING

Papers of particular interest, published within the annual period of review, have been highlighted as:

  • ▪ of special interest
  • ▪▪ of outstanding interest
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REFERENCES

1. Cederholm T, Bosaeus I, Barazzoni R, et al. Diagnostic criteria for malnutrition – an ESPEN Consensus Statement. Clin Nutr 2015; 34:335–340.
2. Matarese LE, Charney P. Capturing the elusive diagnosis of malnutrition. Nutr Clin Pract 2017; 32:11–14.
3▪. Soeters PM, Bozzetti F, Cynober L, et al. Defining malnutrition: a plea to rethink. Clin Nutr 2017; 36:896–901.

Several experts in the field formulate good remarks in response to Ref. [1].

4▪. Gonzalez MC, Correia MITD, Heymsfield SB. A requiem for BMI in the clinical setting. Curr Opin Clin Nutr Metab Care 2017; 20:314–321.

The title of this article may be too much but has the merit to clearly claim what the experts think.

5▪. Delliere S, Cynober L. Is transthyretin a good marker of nutritional status? Clin Nutr 2017; 36:364–370.

A comprehensive review about the interest and the limitations of the use of transthyretin in the exploration of nutritional status.

6▪. Jager-Wittenaar H, Ottery FD. Assessing nutritional status in cancer: role of the Patient-Generated Subjective Global Assessment. Curr Opin Clin Nutr Metab Care 2017; 20:322–329.

Patient-generated SGA is interesting because it favors the interaction between the clinician and the patient.

7▪. Rahman A, Hasan RM, Agarwala R, et al. Identifying critically-ill patients who will benefit most from nutritional therapy: further validation of the ‘modified NUTRIC’ nutritional risk assessment tool. Clin Nutr 2016; 35:158–162.

NUTRIC is specific to ICU. I preferred the initial version which included serum IL-6. IL-6 has been deleted because it is difficult to obtain the result rapidly. In fact, several modern analyzers are able to get a result in few minutes.

8▪. Caillet P, Liuu E, Raynaud Simon A, et al. Association between cachexia, chemotherapy and outcomes in older cancer patients: a systematic review. Clin Nutr 2017; 36:1473–1482.

An excellent systematic review which illustrates how exploring nutritional status is puzzling.

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