Usefulness of routine blood tests in dementia work-up

Recent government reports and strategies have placed the diagnosis and treatment of dementia as a major priority within the NHS. ¹ Guidelines issued from the Royal College of Psychiatrists and the National Institute for Health and Clinical Excellence on the assessment of suspected dementia suggested that all patients being referred to an old age service should receive blood tests. These include a full blood count (FBC), renal profile, liver profile, calcium, erythrocyte sedimentation rate (ESR), C-reactive protein, thyroid function tests, folate and vitamin B12. ^2,3 In contrast, the Scottish Intercollegiate Guidance Network suggested that blood tests should be ordered on clinical grounds. ⁴

An audit by our old age psychiatry service reviewed the laboratory and radiological results of 120 consecutively referred individuals with suspected dementia, all of whom received the blood tests suggested by the Royal College of Psychiatrists guidelines. None had reversible conditions diagnosed on computed tomography; 8.5% had low haemoglobin, 5.7% had a raised ESR, 19% had urea and electrolyte abnormalities and 14% had abnormal liver function tests. Just one patient had thyroid abnormalities and they were already on treatment for this; two had vitamin B12 and folate deficiencies and both individuals had nutritional problems due to advanced dementia.

Previous meta-analyses have shown that less than 0.6% of so-called potentially reversible dementias were reversible. ⁵ Our results suggest that laboratory investigations in dementia work-up are useful in the identification of medical problems that may worsen the patient's overall health or effect suitability to potential treatments. A third way should be taken between the guidelines incorporating their most useful recommendations. Simple tests like FBC, ESR, renal and liver function tests are useful in dementia work-up and should be routinely checked in all individuals with dementia. Less routine tests such as vitamin B12 and folate and thyroid function should only be completed based on clinical grounds.