Laboratory Tests in Diabetes

Question 1

Name four reasons to order lab tests

Answer 1

• Diagnosis - confirm/reject clinical diagnosis
• Monitoring - natural history or response to treatment
• Prognosis - prediction of course
• Screening - detection of sub-clinical disease

Question 2

What are the analytical factors that are required when producing a result for a lab test?

Answer 2

Results are:
• Accurate
• Precise

Question 3

Describe the typicaly shape of a normal distribution curve

Answer 3

Bell shaped

Question 4

What is the reference interval for healthy individuals?

Answer 4

Means +/- 2 standard deviation

Question 5

How do you diagnose diabetes and what are the ranges?

Answer 5

• 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 6

Why is HbA1c measured in diabetes diagnosis?

Answer 6

1. Due to lack of insulin, Glc is not taken up by cells
2. High BG
3. Glc move freely in red cells
4. HbA1c is intracellular (withing RBC)

Question 7

In what situations would you not diagnose diabetes with HbA1c?

Answer 7

• 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 8

What are two different types of tests used for point of care testings in chronic situations?

Answer 8

Urine testing and glucose meter-measurement of capillary blood Glc

Question 9

What can be measured in urine testing?

Answer 9

Glycosuria and ketonuria

Question 10

What are possible faults in the point of care testing which can lead to false results?

Answer 10

• Laboratory error
• Contamination when checking POC glucose
• Blood sample mislabelled
• POC glucose meter malfunction

Question 11

Patient with 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

What is the likely diagnosis?
A) Acute pancreatitis
B) Diabetic ketoacidosis
C) Hyperosmolar hyperglycaemic state
D) Addison’s Disease

Answer 11

B) Diabetic ketoacidosis

• Need insulin to take K+ up

Question 12

Why would Na lower in ketoacidosis?

Answer 12

Fluid is pushed out of plasma as it has high [Glc] which will also dilute other concentrations

Question 13

What is factitious hypoglycaemia?

Answer 13

High insulin levels in absense of elevated C-peptide concentrations

Question 14

What is insulinoma?

Answer 14

Elevated C-peptide level indicative of inuslin secreting tumour

Question 15

Why do you measure for C peptide when looking at insulin levels?

Answer 15

Insulin is initially formed as proinsulin with a C-peptide (which is cleaved off to form insulin)

Question 16

In a patient with high inuslin levels but normal C peptide levels what is the likely diagnosis?

A) Insulinoma
B) Sulfonylurea ingestion
C) Metformin ingestion
D) Insulin administration

Answer 16

D) Insulin administration

Question 17

Name some complications of chronic diabetes?

Answer 17

Macrovascular:
• TIA 
• Stroke 
• Angina 
• MI 
• Cardiac failure 

Microvascular:
• Diabetic retinopathy

• Nephropathy
• Erectile dysfunction
• Foot problems

Question 18

Name biochemical measurment used for diabetes and what they can show

Answer 18

• Glucose - self-monitor BG
• HbA1c - glycaemic control
• Urine albumin/creatinine ratio (ACR) - diabetic renal disease - microvascular screening)
• Lipids - macrovascular screening

Question 19

Why is it important to monitor HbA1c-glycaemic control?

Answer 19

More poorly controlled diabetes -> high HbA1c -> higher risk of complication

Question 20

• Type 2 diabetes 
• HbA1c 30mmol/mol
• LFTs:
       ALT - 65 IU/L (<45)
       BILIRUBIN - 45umol/L (<22)
       ALK PHOS - 72 IU/L (25-110)

What is the likely diagnosis?
A) Glucose meter malfunction
B) Haemolytic anaemia
C) Laboratory error
D) Poor glucose meter technique

Answer 20

B) Haemolytic anaemia
• RBC life span was shortened, so HbA1c was not indicative of diabetic control
• High bilirubin which is a breakdown product of RBCs

Question 21

A 56 year old female with a 12 year history of Type 2 Diabetes was found to have a urine albumin/creatinine ratio of 32 mg/mmol (female reference interval <3.5 mg/mmol)

Which one of the following is not a potential cause of raised ACR?

A) Urinary tract infection
B) Orthostatic proteinuria
C) Diabetic kidney disease
D) Angiotensin converting enzyme inhibitors

Answer 21

D) Angiotensin converting enzyme inhibitors

This is a treatment of raised ACR, not a diagnosis.