Clinical biochemistry - Clinical questions

Question 1

What are the 4 main aims a laboratory test could help with?

Answer 1

Diagnosis
Monitoring
Prognosis
Screening

Question 2

What can cause sample variation prior to sampling?

Answer 2

o Posture
o Timing
o Diet
o Drugs

Question 3

What can cause variation during sampling?

Answer 3

o	Sample Type
o	Sample Tube
o	Tourniquet
o	Centrifugation
o	Requesting errors

Question 4

What random glucose concentration indicates diabetes?

Answer 4

Random venous plasma glucose >11.1mmol/L

Question 5

What fasting glucose concentration indicates diabetes?

Answer 5

Fasting plasma glucose >7.0mmol/L

Question 6

What plasma glucose concentration 2 hrs after a oral glucose tolerance test indicates diabetes?

Answer 6

2 hour plasma glucose >11.1mmol/L in OGTT

Question 7

What HbA1c concentration indicates diabetes?

Answer 7

HbA1c >48mmol/mol (Type 2 Diabetes only)

Question 8

When should HbA1c not be used to indicate diabetes?

Answer 8

• Children and young people
• Suspected Type 1 diabetes
• Symptoms <2 months
• High risk patients who are acutely ill
• Patients taking medication that may cause rapid glucose rise (e.g. steroids)
• Acute pancreatic damage
• Pregnancy/haemolytic anaemia
• Presence of genetic, haematological or illness-related factors that affect HbA1c and its measurement

Question 9

Describe factitious hypoglycaemia

Answer 9

Factitious hypoglycaemia – high insulin levels in absence of elevated C-peptide concentrations, meaning they are injecting too much insulin rather than the body producing more insulin that expected. Can be linked to mental health issues with diabetic patients (particularly young adults with type 1 DM)

Question 10

Describe insulinoma

Answer 10

Insulinoma – elevated C-peptide level indicative of insulin-secreting tumour.

Question 11

What is used to screen for diabetic kidney disease/microvascular disease?

Answer 11

Urine Albumin/creatinine ratio – screening for diabetic renal disease - Microvascular screening

Question 12

What biochemical measurements are monitored in diabetes patients?

Answer 12

• Glucose - self-monitoring of blood glucose
• HbA1c - Glycaemic control
• Urine Albumin/creatinine ratio – screening for diabetic renal disease - Microvascular screening
• Lipids - Macrovascular screening for CV disease

Question 13

What can cause an increased albumin/creatinine ratio?

Answer 13

o UTI
o Orthostatic proteinuria – benign condition, why you should use first urination in the morning to exclude this
o Diabetic kidney disease – ACR is screened for in young type 1 DM patients annually from the age of 12 years

Question 14

What treatment is given to those with diabetic kidney disease?

Answer 14

ACE inhibitors are used to treat and slow progression of albuminuria and diabetic kidney disease

Question 15

What is microalbuminuria an indicator of?

Answer 15

o Marker of vascular endothelial dysfunction
o An important prognostic marker for kidney disease
o In diabetes mellitus
o In hypertension
o In post-streptococcal glomerulonephritis
o Increasing microalbuminuria during the first 48 hours after admission to an intensive care unit predicts elevated risk for acute respiratory failure, multiple organ failure, and overall mortality
o A risk factor for venous thromboembolism

Question 16

What are some metabolic causes of hypertension?

Think 3 S’s

Answer 16

Symptoms - “episodic” intermittent symptoms, phaeochromocytoma

Signs - “appearance”, cushings

Simple - biochemistry: renal disease (urea, creatinine) or primary hyperparathyroidism (calcium and phosphate)