Assessment of a patient's nutrition — methods, advantages and disadvantages

Assessment of a patient's nutrition — methods, advantages and disadvantages

Nutritional assessment in older adults is a two-step process: screening to identify those at risk, followed by assessment for diagnosis and severity grading.

Essentials of Clinical Geriatrics states plainly that anthropometric variables cannot provide a complete description of nutritional status and are not highly correlated with biochemical or haematological indicators — so no single method suffices, and a combination is always required.

The critical questions to answer are: is there reason to suspect malnutrition; of which nutrient and to what extent; what is the pathophysiological mechanism (intake, digestion and absorption, metabolism, excretion or requirement); and what aetiology underlies it.

Distinguish starvation from cachexia: the hallmark of starvation is a rapid response to refeeding, whereas cachexia is remarkably resistant to hypercaloric feeding. In cachexia, appetite is suppressed early, BMI predicts mortality, albumin and transthyretin fall early, CRP is elevated and inflammatory disease is present.

Content: dietary history and 24-hour recall, unintentional weight loss, appetite, chewing and swallowing difficulty, dentition, gastrointestinal symptoms, functional ability to shop and cook, social isolation, alcohol, depression, and a full drug review.

Advantages: free, universally available, identifies the reversible cause, and detects the social and functional determinants that no laboratory test can.

Disadvantages: subjective, time-consuming, and unreliable in dementia or delirium where recall is impaired.

The methods and what each measures: weight — global; body mass index — total body fat; skin folds — percentage fat; waist:hip ratio — central adiposity; upper arm circumference — lean body mass.

Weight is easily obtained and useful, but only in the absence of oedema. Serial weights are more informative than a single value.

Upper arm circumference correlates with lean body mass and is particularly helpful in oedematous patients in whom weight is misleading — but the effect of ageing on lean mass is so great that it remains a poor reflection of nutritional status in older adults.

Calf circumference is an accepted surrogate for muscle mass and is used in the MNA when BMI is unavailable.

Height substitutes: where standing height cannot be measured, use knee-heel height equations — Men = (2.02 × knee height in cm) × (0.04 × age) + 64.19; Women = (1.83 × knee height in cm) × (0.24 × age) + 84.88. For amputees, add the stated percentage for the missing part (single below knee 6.0%, at knee 9.0%, above knee 15.0%, single arm 6.5%, arm below elbow 3.6%).

Advantages: cheap, bedside, repeatable, no laboratory needed — ideal for Indian community and long-term care practice.

Disadvantages: confounded by oedema, ascites, dehydration, kyphosis and vertebral collapse; BMI is unreliable when height cannot be measured; observer variability with skin folds.

Serum albumin is described as a practical indicator of malnutrition in older adults, but liver disease, proteinuria and protein-losing enteropathy must be excluded. A low albumin may indicate malnutrition; a normal or raised albumin does not exclude it.

Thyroxine-binding prealbumin (transthyretin) and retinol-binding protein are more sensitive than albumin and transferrin, because of their shorter half-lives.

Anaemia is one of the earliest manifestations of protein-energy malnutrition and should alert the physician to its possibility; total lymphocyte count may be a very good marker of nutritional problems.

Advantages: objective, numerical, prognostically useful.

Disadvantages — the critical caveat: all these proteins are negative acute-phase reactants and fall with inflammation regardless of nutrition. They therefore reflect disease severity as much as nutritional state, and must be interpreted alongside CRP. Method 4 — Validated Screening and Assessment Tools

Mini Nutritional Assessment (MNA): developed specifically for elderly populations; the full MNA is multidimensional and a short form (MNA-SF) has similar performance. It assesses body mass by either BMI or calf circumference. It was 96% sensitive and 60% specific for body weight loss; a normal baseline score carried a mortality risk of 0.35 (95% CI 0.18–0.66) relative to an abnormal score. It is a powerful prognostic factor, particularly in cancer, and can assess cancer cachexia.

Subjective Global Assessment (SGA): combines history and physical signs. Both MNA and SGA predict mortality in geriatric patients; the MNA classified fewer patients as well-nourished than the SGA, and those it called well-nourished had better 3-year survival — making the MNA the more discriminating tool in older adults.

Other tools: SNAQ (Simplified Nutrition Assessment Questionnaire — a score below 14 signals significant risk of weight loss), MUST, and NRS-2002 for hospital screening.

Advantages: validated, quick, reproducible, usable by nurses, and prognostically powerful.

Disadvantages: screening tools identify risk but do not diagnose the cause; the MNA requires cognitive cooperation and its specificity is modest at 60%.

Pathy's positions comprehensive gerontological assessment as the framework for complex cases with multimorbidity or frailty. It links nutrition to cognition (MMSE, MoCA), mood (GDS), delirium (CAM), falls risk (TUG, SPPB), function (Katz, Barthel, Lawton–Brody), morbidity, medication review, oral and swallowing assessment, constipation screening, and social and socioeconomic support.

The value of this approach is that it converts a measurement into an action plan — dental treatment, meal texture adaptation, help with shopping and meal preparation, meals-on-wheels, treatment optimisation and caregiver support.