pegasus health gp small group education diagnostic dilemmas
TRANSCRIPT
PEGASUS HEALTHGP SMALL GROUP EDUCATION
DIAGNOSTIC DILEMMAS
Diagnostic Dilemmas
Tests covered in this session:
Faecal calprotectin HLA DQ2/DQ8 Homocysteine BNP Vitamin D (a quick look at data)
Case One
Samantha, 34 year old woman: 6/12 diarrhoea Abdo cramps Occasional PR bleeding No weight loss
What else would you like to know?What are the differential
diagnoses?
Case One – Differential Dx
Irritable Bowel Syndrome Coeliac Disease Inflammatory Bowel Disease Lactose Intolerance Infective Diarrhoea Endometriosis Pelvic Inflammatory Disease Cancer in older patient – Colorectal or
Ovarian
What tests (if any) would you order for Samantha?
Faecal Calprotectin Testing
Pros: Helps rule out inflammatory causes of diarrhoea High negative predictive value
Cons: Can be raised in all causes of GI inflammation
(including irritation from NSAID use) Many false positives occur Also increases with age, inactivity, and obesity
Samantha – 6 Months Later
Sister just diagnosed with coeliac disease
Samantha on gluten free diet last 4/52 with only slight improvement in symptoms
Requesting blood test for coeliac disease
What do you do now?Is HLA gene testing appropriate?
Human Leucocyte Antigens & Coeliac Disease
>99% coeliac patients are HLA DQ2/DQ8 positive HLA testing has >99% negative predictive value
20-30% general population HLA DQ2/DQ8 positive• only 3% of these will develop coeliac disease
HLA genes necessary but not sufficient
for development of coeliac disease
Human Leucocyte Antigens & Coeliac Disease
Entire NZ Population
30% of Caucasian population will test positive for HLA DQ2/8
3% of those with a positive HLA will develop coeliac disease
0.1% of those with negative HLA will develop coeliac disease
Illustration for Patients
What Role Does HLA Typing Play?
Not diagnostic for coeliac disease (high rate false +ve)
Negative test rules out coeliac disease
IgA tTG is first-line test for Dx coeliac disease
If positive, go back on gluten for 4wks then test IgA tTG and total IgA
HLA testing not indicated if family history coeliac disease
(~10% prevalence in 1st degree relatives)
Vitamin D Testing
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21-30
31-40
41-50
51-99
100+
92
50
41
3128
14 149 10
611
4 3 4 2 2 2 1 0 1
7 6 4 6 6
GP count by number of tests(9 month period from July 09 – Mar
10)
Total number tests = 2911Number unique patients = 2780
Number of GPs
Number of tests/GP
Indications for Testing Vitamin D
Atypical osteoporosis
Unexplained raised serum alkaline phosphatase or low calcium or phosphate
Unexplained proximal limb pain in older people
Unexplained bone pain, unusual fractures or other evidence suggesting metabolic bone disease
Malabsorption disorders
Long-term anticonvulsant therapy
High risk for deficiency
Consider supplementation for: Institutionalised or house-bound elderly People who are veiled Very dark skin and little sunlight Infants exclusively breastfed by mothers at
risk of deficiency Cholecalciferol 1.25mg 2 stat then 1
monthly No requirement for prior testing or
monitoring
Case 2 - Homocysteine
Bill, 55yrs, long-term patient, few visits
Recent NSTEMI
Committed to changing his lifestyle to reduce his risk of another “heart attack”
Wants his homocysteine level tested
What do you know about homocysteine?
Hyperhomocysteinaemia
Has been linked to: MI, acute coronary syndrome, recurrent coronary
events Premature coronary heart disease Cardiovascular and total mortality Adverse outcomes after angioplasty Carotid artery stenosis Stroke, recurrent stroke, silent brain infarct Venous thromboembolic disease (PE/DVT)
What factors can cause ↑ homocysteine levels?
Is Knowledge of Homocysteine Level Useful in Improving Outcome?
There is evidence that reducing homocysteine levels is of no benefit
There is no evidence to support screening
Routine homocysteine testing is not justified
So… Would you Test Bill?
No. What would you tell Bill?
Knowing Bill’s homocysteine level will not alter his management or risk
Modification of risk factors such as DM, smoking, hypertension, and
hypercholesterolemia shown to be beneficial
Case 3
John, 73y, 1mth history increasing SOB
NSTEMI 18 mth ago
Mild hypertension, hypercholesterolaemia
On Examination• Temp 37.6, P 88 reg, BP 150/95• HS dual and nil• Chest dull at bases, some coarse creps• Trace pedal oedema
What else do you want to know?What are the differential diagnoses?What investigations would you do?
BNP (Brain Natriuretic Peptide) Secreted in response to ventricular
distension
High negative predictive value useful for ruling out HF
Diagnosing HF is difficult in Primary Care:- Early symptoms often mild and non-
specific- Clinical findings neither specific nor
sensitive- Echo not readily available
Back to John…
BNP = 52 pmol/L What does this mean?
A normal BNP in an untreated patient effectively rules-out heart failure
An intermediate BNP does not rule out heart failure
A high BNP indicates heart failure but does not exclude other chest/heart problems
< 30 Low – HF unlikely (2%)30 – 80 Indeterminate – HF still possible>80 High – HF likely (95%)
Alternative Scenario
What if John’s BNP was 217 pmol/L? (High)
What would this mean?
How would you manage him?
Can you use BNP testing to guide optimal drug treatment of John’s
HF?
When is BNP Useful in General Practice?
High BNP supports diagnosis of HF o but does not exclude other conditions
Low BNP can rule out HF in an untreated patient
May have role in known HF patientso for helping diagnose cause of acute dyspnoea
When is BNP not Useful in General Practice?
No role in screening for asymptomatic LV
dysfunction monitoring well patients who have
HF excluding CHF in those already on
therapy
Not recommended for guiding drug titration in HF patients with obvious clinical
diagnosis of HF
BNP Data
1 to 5 6 to 10 11 to 15
16 to 20
21 to 25
26 to 30
31 to 35
36 to 40
41 to 45
46 to 50
51 to 100
> 1000
20
40
60
80
100
120
140
160
180
200
175
85
57
22 20 169
4 7 38
2
GP count by number of BNP tests(9 month period from July 09 – Mar
10)Total number tests = 4563Number unique patients = 3728
Number of GPs
Number of tests/GP
Summary - Diagnostic Dilemmas
‘Off-schedule’ tests were developed in 2° care - Place in 1° care not yet established
Only test if it will influence management
Most of these tests have significant limitations
Test results may be misleading
Paramount to use clinical judgment
Take Home Messages
Faecal Calprotectin • second line test • may help rule out Inflammatory Bowel Disease
in young patient with chronic diarrhoea
HLA DQ2/DQ8• Not recommended to diagnose Coeliac Disease• 30% of Caucasians express these markers
Vitamin D• Don’t test, just treat
Take Home Messages Cont’d
Homocysteine • Reducing levels does not improve patient
outcomes• No role for testing
BNP• If normal, useful to rule out HF• If high, may support diagnosis of HF• May be raised by other conditions that strain the
heart
Sometimes it is best not to do a test!