Clinical biochemistry in diabetes

Question 1

why are lab tests used

Answer 1

diagnosis
monitoring
prognosis
screening

Question 2

what 2 characteristics do good tests have

Answer 2

accuracy - can the method produce the correct result

precision - can it do this repeatedly

Question 3

why are lab tests used in diabetes

Answer 3

diagnosis

monitoring - acute, chronic

Question 4

what lab tests can help diagnose diabetes

Answer 4

Random venous plasma glucose >11.1mmol/L

Fasting plasma glucose >7.0mmol/L

2 hour plasma glucose >11.1mmol/L in OGTT

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

If asymptomatic, requires confirmation by repeat testing on another day

Question 5

what is monitored in HbA1c

Answer 5

HbA1c - intracellular within RBCs

high blood glucose levels

• glucose not taken into cells due to lack of insulin (absolute or relative)
• glucose moves freely into RBCs

Question 6

when would you not use HbA1c to aid diagnosis

Answer 6

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

Presence of genetic, haematological or illness-related factors that affect HbA1c and its measurement

Question 7

what lab tests can aid in acute monitoring

Answer 7

urine testing (dipstix):
glycosuria
ketonuria

glucose meter:
measurement of capillary blood glucose

Question 8

CASE: 21 year old student

• thirst, polyuria and weight loss over the last two months; - became unwell with flu-like symptoms and began vomiting.

Urinalysis-
Glucose ++++
Ketones ++

Dehydrated, tachypnoeic and generalised abdominal tenderness, admitted to the surgical ward on 40% O2

diagnosis?

Answer 8

diabetic ketoacidosis

Question 9

what is factitious hypoglycaemia

Answer 9

high insulin levels in absence of elevated C-peptide concentrations

Question 10

what is insulinoma

Answer 10

elevated C-peptide level indicative of insulin-secreting tumour

Question 11

what are some of the chronic complications of diabetes

Answer 11

macrovascualr disease

• TIA, stroke
• angina, MI, cardiac failure

microvascular disease

• diabetic retinopathy
• nephropathy
• erectile dysfunction
• foot problems

Question 12

what lab tests are involved in chronic diabetes monitoring

Answer 12

Glucose (self-monitoring of blood glucose)

HbA1c (Glycaemic control)

Urine Albumin/creatinine ratio (Diabetic renal disease - Microvascular screening)

Lipids (Macrovascular screening)

Question 13

what is ACR (albumin/creatinine ratio) used to screen for

Answer 13

diabetic kidney disease