Practice Nurse

Interpreting Biochemistry Tests

Biochemical investigations are crucial in the management of a vast array of disorders. They are some of the most commonly requested tests and much diagnostic information can be gleaned from them. Composed of 10 questions, this resource assesses the users knowledge on commonly requested biochemical tests and their relationship with the diagnosis. Complete the 10 questions to obtain a certificate for 1hr of continuous professional development to include in your annual portfolio.

On successful completion of this resource, the user should be able to:

Recognise the common abnormalities noted on biochemistry requests such as U+Es, liver function tests and calcium metabolism

Understand the reasons for these abnormalities and formulate potential diagnoses

Reference ranges from Scarborough Hospital

some of the most commonly requested tests and much diagnostic information can be gleaned fromtheir correct interpretation. Composed of 10 assessment questions, this resource assesses the userknowledge on commonly requested biochemical tests and their relationship with the diagnosis.Complete the 10 questions to obtain a certificate for 1hr of continuous professional development toinclude in your portfolio submission.

On successful completion of this module, the user should be able to:

A 72 year old female attends clinic with a degree of confusion and increased lethargy. Her results reveal:

Which of the following is the likely cause for these results?

This woman has a low sodium level, hyponatraemia, which is probably responsible for her symptoms. This is one of the most common electrolyte disturbance seen in clinical practice. Sodium is needed by the body for many functions, including the maintenance of fluid balance, regulation of blood pressure, and for the nervous system to function normally.
Hyponatraemia is defined as a serum sodium of
there are a number of different causes for hyponatraemia, these include hypothyroidism, addison's disease, but it can also be drug induced which is the most likely explanation here. SSRI's such as fluoxetine are a frequent cause of hyponatraemia.

http://www.patient.co.uk/doctor/Hyponatremia.htm

Question 1

A 65 year old man attends clinic as he has recently started some treatment for high blood pressure and has returned for a blood test. His results show:

Which of the following medications is likely to have caused this blood result?

This man has a low potassium - hypokalaemia. Potassium is needed for cells, especially nerve and muscle cells, to function properly. Hypokalaemia is associated with feeling of tired and weak, muscle spasms, and can even cause life threatening arrhythmias if there is severe hypokalaemia. The most likely cause of this in this case is bendrofluazide as this drug causes a loss of potassium as well as sodium. Bendrofluazide is a drug commonly used in the treatment of hypertension. Other causes of hypokalaemia include kidney disease, conn's syndrome and diarrhoea. Potassium can be replaced with supplements, and a potassium sparing diuretic can be used, such as spironolactone.

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001510/

Question 2

A 55 year old male attends clinic as he has been started on a treatment for high blood pressure and returns a fortnight later to get his blood checked. He has been feeling generally well. His results show:

Which of the following drugs is most likely to have caused this picture?

Ramipril is an ACE inhibitor and it's used in practice to reduce blood pressure. It does this by blocking the Angiotensin Converting Enzyme (ACE), which converts angiotensin I to angiotensin II. Therefore, ACE inhibitors such as ramipril reduce the angiotensin II concentration, which leads to a reduced aldosterone concentration. Aldosterone works on the kidney tubule to cause potassium excretion and sodium retention, so blocking this hormone can cause a retention of potassium, hence 

. Hyperkalaemia can also be caused by kidney failure, other drugs such as spironolactone and also dehydration.

http://www.patient.co.uk/doctor/Hyperkalaemia.htm

Question 3

A 30 year old woman has attended clinic because of frequent muscle cramps. She has a past history of hypothyroidism which is treated. Her investigations return as follows:

What is the most likely cause for this blood picture?

This patient already has hypothyroidism, an autoimmune condition, and now has developed a 

. The symptoms commonly seen with hypocalcaemia are paraesthesia, tetany, and muscle cramps. In this patient, it is likely to be due to hypoparathyroidism. This could also be due to an autoimmune cause. The diagnosis could be confirmed by measuring the PTH concentration. Other causes of low calcium include vitamin D deficiency (secondary hypoparathyroidism) and certain drugs such as bisphosphonates, phenytoin.

http://emedicine.medscape.com/article/241893-differential

Question 4

A 72 year old woman comes to clinic complaining of tiredness and constipation. She has a history of high blood pressure for which she takes atenolol and amlodipine. Her blood tests show:

What is the most likely cause for her presentation and results?

This patient has typical symptoms associated with 

. Other symptoms include depression, bone aches and pains as well as renal stones. In this older woman, the most probable cause for the high calcium is hyperparathyroidism. The parathyroid hormone causes a release of calcium from bones, leading to an increased concentration in the blood. A raised PTH concentration would confirm the diagnosis. Other causes of hypercalcaemia include cancer, hypervitaminosis D, sarcoidosis and certain drugs such as thiazide diuretics.

http://www.patient.co.uk/health/Thyroid-and-Parathyroid-Glands.htm

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002561/

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002195/

Question 5

A 45 year old woman attends clinic as she has been aware of weakness, muscle cramps and feeling down for the last few months. She feels that something is not quite right. She has a history of coeliac disease. Her blood results reveal:

What is the most likely explanation for her presentation?

This young woman has a low calcium which explains her presentation, but she also has a high PTH concentration. Here, the PTH is appropriately high as it is trying to correct the low calcium. This is secondary hyperparathyroidism. In this case the likely cause is 

 which is very common particularly in individuals with absorption problems such as coeliac disease. Vitamin D induces synthesis of a calcium-binding protein in the intestinal cells, which facilitates the efficient absorption of calcium into blood. Therefore with low vitamin D levels, the PTH secretion is increased to try to compensate for the low calcium. A prominent effect of secondary hyperparathyroidism is decalcification of bone, leading to pathologic fractures. Vitamin D supplements can be given to correct this.
In hypoparathyroidism, the PTH and Calcium would both be low. In primary hyperparathyroidism, both calcium and PTH would be high.

http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001361/

Question 6

A 72 year old female attends clinic complaining of aches and pains particularly in the shoulders and hips which have deteriorated over the last few months. She has also been aware of some weight loss. There are no specific abnormalities noted on examination. Her investigations show:

The clear abnormality here is the markedly elevated Erythrocyte Sedimentation Rate ? ESR ? which together with the symptoms point to a diagnosis of 

. This is an inflammatory condition of unknown aetiology which typically affects the elderly. It is treated with steroids which usually produce a good result. An important complication which affects around one in five people with polymyalgia rheumatica is a serious condition called giant cell arteritis. This causes inflammation in the body?s medium and large arteries, resulting in symptoms such as persistent headaches with scalp tenderness, pain in the jaw muscles when chewing (jaw claudication) and impaired vision. Giant cell arteritis is regarded as a medical emergency and without prompt treatment it can cause permanent blindness so it is important to recognise this condition early.

http://www.nhs.uk/conditions/Polymyalgia-rheumatica/Pages/Introduction.aspx

Question 7

A 25 year old female comes back to clinic anxious for the results of her blood tests. She has had a two week history of feeling unwell, has been down and has lost some weight. There was nothing to find on examination. Results reveal:

What can you conclude from these results?

We can't really conclude anything from these tests, as the results are entirely normal. The importance is to rely on clinical impression which is supported by the results that you request. In this case, the patient's history may suggest a potential diagnosis of anxiety/depression and this should be explored further with the patient. The latter would be a diagnosis of exclusion as it is important to exclude any occult pathology.

Question 8

A 43-year old man who is an accountant and has been under a lot of financial pressure,attends clinic as he has been feeling depressed and experiences pain in his upper right abdomen associated with nausea. Nothing is noted on clinical examination. His investigations show:

What is the most likely explanation for his presentation?

This man, who suggests a history of depression, has elevated Alkaline Phosphatase (ALP) and gamma GT concentrations on this liver function test. The ALT and AST are normal. Elevation of the seenzymes are associated with a hepatitis. In this case, this biochemical picture is most likely to be 

 and his history of upper abdominal pain and nausea is suggestive of a alcoholic hepatitis. Isolated raised gamma GT is an indicator of alcohol abuse (however, it can be normal even with heavy alcohol consumption) His consumption of alcohol should be explored at the next clinic visit and he should receive appropriate counseling.ALP can also be raised in bone disease, so in elderly patients it's important to consider fractures, or osteomalacia.

http://www.patient.co.uk/doctor/Abnormal-Liver-Function-Tests.htm

Question 9

A 55-year old man attends clinic feeling unwell with the flu. For reasons that do not seem clear in the notes the following blood tests have been performed with the results revealing the following:

What is the most likely cause for these results?

This patient has an isolated mild elevation of his bilirubin which is quite co-incidental to his presentation with the flu. This suggests a condition called 

 resulting in the abnormal handling of bilirubin higher levels in the blood. An enzyme called uridine-diphosphate glucuronosyltransferase (UGT) helps the liver cells to process the bilirubin. People with Gilbert's syndrome have a reduced level of this enzyme and so bilirubin can build up in the bloodstream. It is very common occurring in approximately 1 in 20 people and does not typically cause any problems with health. It is important to recognise this condition to avoid further, unnecessary investigation.

http://www.patient.co.uk/health/Gilbert%27s-Syndrome.htm

Interpreting Biochemistry Tests

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