Clinical Biochemistry - Clinical Questions - Laboratory Tests in Diabetes Flashcards
Why Use Laboratory Tests ?
Diagnosis - Confirmation or rejection of clinical diagnosis
Monitoring - Natural history or response to treatment
Prognosis - Prediction of course or outcome of the disease
Screening - Detection of sub-clinical disease
What are 2 important analytical factors to consider?
Accuracy - can the method produce the correct result
Precision - can it do this consistently
Pruple - Precise means same answer if you test multiple times but not accurate
Green is not precise
Yellow is precise and accurate
what is the reference range?
Reference range = range between which the result can be in
Calculate and add 2 SD on each end
Can be out with the reference interval and be well or you can be in it and ill
what 95% of the normal population is in
What is the use of biochemistry tests in diabetes?
diagnosis
monitoring - acute and chronic
how do you diagnose diabetes?
- 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
HbA1c - What are we monitoring?
Do not use HbA1c for diagnosing diabetes in what?
Children and young people (Not in children and young people as often have type 1 diabetes and glucose comes on rapidly and you may miss it and get a false negative)
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 (RBC turn over more rapid in pregnancy so it will come in lower than it should)
Presence of genetic, haematological or illness-related factors that affect HbA1c and its measurement
How is point of care testing carried out in diabetes?
URINE TESTING:
- GLYCOSURIA
- KETONURIA
GLUCOSE METER- MEASUREMENT OF CAPILLARY BLOOD GLUCOSE
Not used for diagnosis
Case 1 – 13 year old female with known type 1 diabetes mellitus admitted to A&E because of drowsiness and vomiting
POCT Testing - A Point of Care finger prick test in A&E showed blood glucose of 20 mmol/L
The FY2 was going to give her some more insulin but decided to confirm the result by sending a blood sample to the lab
The Lab result was returned at 1.8 mmol/L
Why are the results different?
A) Laboratory error
B) Contamination when checking POC glucose
C) Blood sample mislabelled
D) POC glucose meter malfunction
B
The girls fingers had been contaminated with vomit after she had been given some orange squash to drink; this led to the seriously high blood glucose concentration result by POCT
Case 2 - 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
What is the most likely diagnosis?
A) Acute pancreatitis
B) Diabetic ketoacidosis
C) Hyperosmolar hyperglycaemic state
D) Addison’s Disease
B
Can present with abdomen pain aswell
Biochemistry results:
Ref = 95% of normal population to have
Glucose so high so water moves down osmotic gradient out of cells
High potassium can cause arrhythmias – high as acidosis as cells have lots of hydrogen ions so potassium moves out of cells
Urea and creatinine tells us about kidney function
Bicarbonate gets used up to buffer the acid
Case 3
A 21 year old woman with diabetes mellitus was admitted to the medical ward for the investigation of recurrent hypoglycaemic episodes despite her insulin dose being reduced
Routine biochemistry results attached
ALT a bit high
Do cortisol to make sure she doesn’t have Addison’s disease as that will present with hypoglycaemia and if type 1 diabetes more likely to have other autoimmune conditions
729 is high - anything above 505 is high so its fine - body producing cortisol to counteract hypoglycaemic
Factitious hypoglycaemia - high insulin levels in absence of elevated C-peptide concentrations
Insulinoma - elevated C-peptide level indicative of insulin-secreting tumour
Insulin - 165 mU/L (<13)
C-Peptide - undetectable
What is the most likely diagnosis?
A) Insulinoma
B) Sulfonylurea ingestion
C) Metformin ingestion
D) Insulin administration
D
What are some chronic complications of diabetes?
What are some biochemical measurements in diabetes: chronic?
Glucose (self-monitoring of blood glucose)
HbA1c (Glycaemic control)
Urine Albumin/creatinine ratio (Diabetic renal disease - Microvascular screening)
Lipids (Macrovascular screening)
What does HbA1c glycaemic control tell us?
HbA1c tells us about the risk of complications
Higher the HbA1c the higher the risk of complications
Case 4
64 year old lady with Type 2 Diabetes Mellitus
HbA1c 30mmol/mol (pretty low) (37mmol/mol five months previously)
Home blood glucose monitoring – glucose results consistently 17-18mmol/L
LFTs –
ALT 65 IU/L (<45)
BILIRUBIN 45umol/L (<22)
ALK PHOS 72 IU/L (25-110)
What is the most likely explanation?
A) Glucose meter malfunction
B) Haemolytic anaemia
C) Laboratory error
D) Poor glucose meter technique
B
HbA1c is lower as haemolytic anaemia means RBC have a shortened life time
This women actually had poorly controlled diabetes
Bilirubin high as it is a breakdown product of haemoglobin
Could have been any of the others
Case 5
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
D
ACE inhibitors are used to treat diabetic problems
UTI can cause a raised ACR
Orotstatic proteinuria – when stand get some leakage in the kidney
Diabetic kidney disease does put it right up
