Biochemistry in the elderly
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.
Disease in old age
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 |
