Investigations for the older person

If you decide that your management requires further investigation. The following are worth thinking about;

Interpretation of blood results

Urea

The middle range can represent severe dehydration in older patients.

Creatinine

Low muscle bulk can mask poor renal function and that there are limitations of the Cockcroft-Gault equation for calculating eGFR in older patients when diagnosing and staging kidney disease. CKD is often overdiagnosed.

Electrolytes

sodium <125mM/L can cause confusion and tiredness; sodium <115mM/L can cause seizure, coma, death. The rate of change is important also. Some people run a chronically low sodium of around 125 which is unlikely to be causing symptoms.

Glucose

Higher risk of hypoglycaemia in older patients, due to the age-associated decrease in the autonomic
response to hypoglycaemia.


Liver Function Tests

Paget’s disease should only be considered if elevated alkaline phosphatase in otherwise normal liver
function tests. It could also be elevated for weeks after a sustained fracture.


Calcium, C Reactive Protein (CRP), Thyroid Function Tests

Sick euthyroid syndrome can occurr during acute illness. If a hypothyroid older patient is successfully
treated, but clinically not feeling better, consider further tests for concomitant autoimmune conditions like pernicious anaemia, Addison’s disease.

Urinalysis

Asymptomatic bacteria does not necessarily indicate urinary infection but new onset incontinence should be investigated with urine culture.


Full Blood Count

Haemoglobin (Hb) levels gradually decline from the age of 60. Around 20 per cent of older patients are anaemic due to disease, and they may also suffer from marrow suppression (myelodysplasia).

Fluid overload can a cause fall of Hb level as can fluids in a previously dry patient

Erythrocyte Sedimentation Rate (ESR)

Can be useful for monitoring/screening some conditions in older people. It is usually very
high (>90mm/hr) in giant cell arteritis, metastatic cancer, chronic infection.

In patients older than 70 years, values of up to 35mm/hr for female and 30 mm/hr for male
patients can be normal.