Biochemistry in the elderly

Published on 01/03/2015 by admin

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Biochemistry in the elderly

By the year 2050 more than 20% of the world’s population will be over 65 years of age. As the population ages, more clinical biochemical resources will need to be directed towards the problems of the elderly population.

There is considerable variation in the onset of functional changes in body systems because of age. Many organs show a gradual decline in function even in the absence of diseases; but since there is often considerable functional reserve, there are no clinical consequences. The problem facing the clinical biochemist is how to differentiate between the biochemical and physiological changes that are the consequences of ageing, and those factors that indicate disease is present. Just because the result of a biochemistry test in an elderly patient is different from that in a young person does not mean some pathology is present. Serum creatinine is an example. Renal function deteriorates with age (Fig 74.1) but finding a serum creatinine of 140 µmol/L in an 80-year-old woman should not be cause for alarm. Indeed, this creatinine result may represent a remarkably good glomerular filtration rate considering the age of the patient.

The interpretation of biochemical measurements in the elderly requires that laboratories establish age-related reference ranges for many of the tests undertaken.

Disease in old age

Some diseases are more commonly encountered in the elderly than in the young. In addition, common diseases may present in a different way to that in the young. Elderly patients may have more than one disease or may take several medications that mimic or mask the usual disease presentation.

The admission of a patient for geriatric assessment involves a degree of ‘screening’ biochemistry that may point towards the presence of disorders that may not be suspected (Table 74.1).

Table 74.1

Biochemical assessment in a geriatric patient

Test Associated conditions
Potassium Hypokalaemia
Urea and creatinine Renal disease
Calcium, phosphate and alkaline phosphatase Bone disease
Total protein, albumin Nutritional state
Glucose Diabetes mellitus
Thyroid function tests Hypothyroidism
Haematological investigation and faecal occult blood Blood and bleeding disorders

The metabolic diseases that occur most commonly in the elderly and may present in unusual ways include:

Thyroid disease

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