Gastro-Intestinal Function Testing and GI Disease Flashcards
What are Signs and Symptoms of GI disease?
- Altered bowel habits: Frequency, Watery/Diarrhoea, Blood, Mucous, Steatorrhea
- Abdominal/chest pain exacerbated by food intake
- Weight loss
- Nausea, Vomiting, Dysphagia
What are signs of Specific Nutritional Deficiencies?
- Anaemia: Fe/B12/Folate
- Osteomalacia/Rickets: Vit D
- Easy bruising/bleeding: Vit K
What are Inflammatory Bowel Disease?
- A chronic inflammatory condition of unknown aetiology affecting any part of the intestine.
- Split into Ulcerative Colitis and Crohns Disease
What are features of Ulcerative Colitis?
- 1-2/1000 UK
- Confined to colon
- Extends proximally from rectum
- Disease confined to mucosa
What are features of Crohns Disease?
- 0.5-1.0/1000 UK
- Affects any part of GI tract
- Inflammation through full thickness of bowel wall
- Fistulation, abscess formation, stricturing
How is IBD diagnosed?
- History & examination
- Bloods: Raised platelets/white cells, Raised CRP/ESR
- Colonoscopy or Sigmoidoscopy
- Histology
- Faecal calprotectin (36 kDa)
What is Faecal Calprotectin?
Calcium and zinc binding protein that present in cytosol in neutrophilic granulocytes. Faecal levels correlate well with neutrophilic infiltration of intestinal mucosa
- >2000 µg/g = Severe inflammation
- >1000 µg/g = Severe inflammation
- >100 µg/g = Active Inflammation
- 51-100 µg/g = Equivocal
- 0-50 µg/g = Normal
What is the Use of Faecal Calprotectin?
Differentiate IBD from IBS
- Primary Care
- Reduce number of patients referred for endoscopy
Assessment of disease activity in patients with known IBD
Monitoring response to treatment
What are the Faecal Protectin Assays?
- Semi quatitative POCT: Buhlmann Quantum Blue
- ELISA: Buhlman, CALPRO, Immunodiagnostik
- Stand-Alone Analyser: Thermo ELIA (Phadia)
What are features of Colorectal Cancer?
- Most common malignancy in Western world
- 2nd most common cause of cancer death. Improved prognosis if detected early
- Gold standard diagnosis and detection carcinoma and early adenomas/polyps = colonoscopy/sigmoidoscopy
What are tumour markers of Colorectal Cancer?
CEA
- Non-specific marker of colon cancer.
- Also elevated in other malignancies such as Pancreatic, Peritoneal, Ovarian
- Also elevated in benign conditions such as Ascites, Pancreatitis, Liver disease
CA19-9
- Non-specific marker of pancreatic cancer
- Also elevated in other malignancies such as Colon, Biliary tract
- Also elevated in benign conditions such as Pancreatitis, Hepatitis
Which tests are used for screening Colorectal Cancer?
- Guaiac faecal occult blood (FOB) test
- Faecal Immunochemical Test for Hb
- Tumour M2-PK
- Faecal tumour DNA
How is Guaiac faecal occult blood (FOB) test conducted?
- Patient collects and smear faeces on the card. Peroxide added to card.
- Peroxidase activity of Hb oxidises guaiac in presence of H2O2 inducing blue colour formation
What are Pitfalls of Guaiac faecal occult blood (FOB) test?
Dietary restriction required 3 days prior
- False +ve = Red meat, Turnips, Horseradish, Broccoli, Cauliflower
- False –ve = Vitamin C (counter the oxidation)
Non/intermittent bleeding lesions
Multiple sample collections
Poor sensitivity for detection of adenoma/carcinoma 15-50%
What are features of Faecal Immunochemical Test for Hb in Colorectal Cancer?
- Qualitative or quantitative assays available
- Recommended faecal test - European guidelines colorectal cancer screening & diagnosis
What are Advantages of FIT over Guaic FOB?
- Higher sensitivity to presence of blood
- Higher specificity – reduced false positives
- Fewer medication interferences
- Fewer dietary interferences
- Quantitative
- Dedicated automated analysers
What are disadvantages of FIT over Guaic FOB?
- More expensive
- Can still miss bleeding if intermittent bleeding or very low-level bleeding
What is Tumour M2-PK?
- M2 isoform of pyruvate kinase (PK) predominant isoform in rapidly proliferating cells eg fibroblasts, lung, bladder, kidney etc. M2-PK can exist in two forms
- Almost all PK in tumour cells is of dimeric form hence cell metabolism favours tumour growth = Tumour M2-PK
- Available as quantitative ELISA or rapid test for stool samples
What are the forms of Tumour M2-PK?
Tetrameric form
- Highly active
- Favours glycolytic flux, converting phospoenolpyruvate to pyruvate
Dimeric form
- Virtually inactive
- Favours build up and channelling of early glycolytic pathway intermediates into synthetic processes eg nucleic acid, amino acid and fatty acid synthesis
- Dimerisation induced by oncoproteins
What are appplications of Tumour M2-PK?
CRC Stool Screening
- Improved sensitivity and specificity compared to gFOBT
- Single stool sample
- No dietary interferences
- No false positives due to other causes of GI bleeding
- Detection not dependent on tumour/adenoma bleeding
- Quantitative ELISA or qualitative POCT available
Serum tumour marker
- GI, pancreatic, breast, melanoma, thyroid, lung, renal, oesophageal, ovarian, cervical
- Early detection of relapse
- Monitoring / Response to therapy
- Staging
What is the Pathophysiology of Pancreatitis & Pancreatic Insufficiency?
- Pancreatic over stimulation / injury
- Co-localisation of lysosomal enzymes with pancreatic exocrine enzymes
- Accumulation of activated intracellular trypsin
- Pancreatic tissue destruction and release of further enzymes from damaged cells
- Profound acute inflammatory response, pancreatic tissue necrosis and ischaemia
What is the Aetiology of Acute Pancreatitis?
- G = Gallstones
- E = Ethanol
- T = Trauma
- S = Steroids
- M = Mumps
- A = Autoimmune (SLE, Sjogrens)
- S = Scorpion Sting
- H = Hypertriglyceridemia, Hypercalcaemia
- E = Endoscopic retrograde cholangiopancreatography (ERCP)
- D = Drugs (steroids, opiates, estrogens, azathioprine)
What is the aetiology of Chronic Pancreatitis?
All causes of acute pancreatitis if prolonged, plus:
- Cystic fibrosis
- Hereditary haemochromatosis
- Schwachman-Diamond syndrome
- SBDS gene
- 2nd most common cause pancreatic insufficiency in children
What are Historical Tests for Pancreatitis?
Faecal fat
- 72 hr faeces collection and measurement of fat content
- No longer used other than situations where malabsorption is strongly suspected and standard investigations proven negative
Direct pancreatic exocrine tests
- Intubation of duodenum or pancreatic duct
- Collection of secretions for analysis of bicarbonate and pancreatic enzyme activity following stimulation with a test meal or hormones
Indirect pancreatic exocrine test
- Administration of test substance from which a measurable marker is released following pancreatic enzymatic cleavage. Marker subsequently excreted and measured in the urine
- NT-PABA
- Fluorescein dilaurate
What are biochemical tests for Pancreatitis
- Amylase
- Lipase
- Faecal Elastase
What are features of Amylase measurement in Panceatitis?
- Serum amylase >3x upper limit of normal (ULN) strongly suggestive of pancreatitis, cut-off most often used in biochemistry labs
- Concentrations begin to rise within hrs onset of pancreatic injury, and falls after 3-5 days
- Urine amylase remains elevated several days after serum concentrations fall to normal, hence good test for late presentation
- Serum amylase within ref range in up to 30% cases acute pancreatitis
What can lead to false positives in Amylase measurements of Pancreatitis?
- Peptic ulcer disease
- Cholecystitis
- Intestinal obstruction
- Salivary gland disease
- Pneumonia
- Head injury
- Renal failure
- Diabetic ketoacidosis (DKA)
- Anorexia nervosa
What is Macroamylase?
Benign cause of elevated serum amylase. Low urine amylase as large macro complex not filtered at glomerulus
Amylase-creatinine clearance:
- <1% consistent with macroamylasaemia
- >5% consistent with AP
What are features of Lipase measurements for Pancreatitis?
- Longer half life than amylase and higher activity hence better than amylase for late presentation patients
- Similar sensitivity and specificity to amylase, but slightly more expensive
- If elevated serum amylase but ?acute pancreatitis, can measure concurrent lipase
What other diseases can lead to elevated Lipase?
- Peptic ulcer disease
- Mesenteric ischaemia
- Renal failure
- Bone fractures
What are features of Faecal Elastase?
Pancreatic Elastase-1
- Pancreas specific protease that passes unchanged through the intestine
- Excellent test of severe pancreatic insufficiency but less sensitive in mild and moderate disease
- Potential for false positives in watery stool samples
- Also useful for monitoring CF patients
- Non-invasive
What are features of Cystic Fibrosis?
- Autosomal recessive ~1/2500 N.European
- Mutation in Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. CFTR protein regulates movement of Cl- and Na+/H2O across epithelial membranes – present in cells lining entire GI tract
- Leads to multi organ dysfunction affecting Lungs, Pancreas, Liver, GI Tract
- Most common mutation = ∆F508, ~1/30 heterozygous carriers
What are signs and symptoms of CF?
- Pancreas: Pancreatitis, Steatorrhea, Diabetes, Fat soluble vitamin deficiencies
- Lungs: Bronchiectesis, Pneumonia , Respiratory failure, Hemoptypsis
- GI: Meconium Ileus, Volvulus, Steatosis, Splenomegaly, Biliary cirrhosis
- Other: Growth failure, Infertility, Delayed puberty, Osteoporosis
how is Newborn Screening for CF conducted?
- Day 5-8 heelprick bloodspot
- CF screening test = Immunoreactive Trypsinogen (IRT)
- Screening test only, not 100% sensitive or specific hence will be false positives and false negatives
- Confirmation by repeat IRT and DNA analysis of common CFTR mutation panel. Quality of bloodspot important
How can blood quality for CF screening be preserved?
- No overlaying
- Must fill collection circle
- Minimise ‘milking’
What is the gold standard for CF diagnosis?
Sweat Test is the gold standard. It is performed after 2 weeks of age and has requirements such as:
- >3Kg
- Normally hydrated
- No systemic illness
- No eczema at sweat collection site
- Not on corticosteroids
How Sweat Test analysis conducted?
Sweat collection = Pilocarpine Iontophoresis
- Measure sweat Cl- concentration on ISE, also measure Na+ concentration to ensure no discrepancy
What are the cutoffs used for Sweat Tests?
Guidelines, sweat Cl- concentration cut-offs:
- >60 mmol/L = supports diagnosis of CF
- 40-60 mmol/L = equivocal, requires repeat (or 20-60 mmol/L if <6 months age)
- <40 mmol/L = low probability for CF (or <30 mmol/L if <6 months age)
2 positive results on 2 separate days essentially diagnostic for CF, should be confirmed with DNA analysis
What are GI disorders leading to Chronic Diarrhoea?
- GI malignancy
- GI inflammation
- Small bowel malabsorption
- Pancreatic insufficiency
- Motility disorders
What is the definition of Chronic Diarrhoea?
- Passage of ≥3 loose or liquid stools per day for >4 weeks, and/or daily stool weight >200 g/day
What is the Clinical History for Chronic Diarrhoea?
Organic vs Functional disease
- History <3 months, Nocturnal/Continuous, Weight loss
Signs of Malabsorption
- Steatorrhea, Signs and symptoms of specific nutritional deficiencies
Signs of Inflammatory Disease
- Liquid stools, Blood/mucous, Abdominal pain
What are causes of Chronic Diarrhoea?
- GI Inflammation: Crohn’s, Ulcerative Colitis, Coeliac Disease, Malignancy
- Pancreatic Disease: Pancreatitis, Malignancy, Cystic Fibrosis
- Endocrine: Hyperthyroidism, Hypoparathyroidism, Diabetes Mellitus, Addison’s, VIPoma, Gastrinoma, Carcinoid
- Others: Lactose Intolerance, Drugs, Alcohol, Laxative Abuse
What are tests for the causes of Chronic Diarrhoea?
- GI Inflammation: Test with Faecal Calprotectin, Anti-tTG/Endomysial Ab, Tumour Marks FOB/FIT
- Pancreatic Disease: Test with Amylase, Lipase, Faecal Elastase, Tumour Markers IRT/Sweat Test
- Endocrine: Test with TFTs, Bone/PTH, OGTT/HbA1c, Cortisol/SST, Gut hormones, 5HIAA
- Others: Test with Faecal Reducing Substances, Urine Laxative Screen, GGT/CDT
What is the Biochemical Tests for Liver Fibrosis?
- Enhanced Liver Fibrosis (ELF) Test
- Used a screening test in primary care population to reduce patients referred for needle biopsy of liver
What are Biochemical Markers measured in the Enhanced Liver Fibrosis?
- Hyaluronic acid (HA)
- Procollagen III amino terminal peptide (PIIINP)
- Tissue inhibitor of metalloproteinase 1 (TIMP-1)
What are disadvanatges of Liver Biopsy?
- Morbidity & mortality
- Samples very small portion of liver
- Costly & time consuming
- Operator variability / error rate
- Cannot perform repeat biopsy at short intervals
What are advanatages of ELF test?
- Identify patients at early stages liver fibrosis before progressing to cirrhosis
- Cost effective and safer compared to biopsy
- Single blood test no patient preparation required
- As good as Fibroscan
What are Disadvantages of ELF test?
- Screening test, therefore, not 100% sensitive or specific
- False positives and false negatives
- Currently only available on Siemens analysers
What are other GI disease investigations?
- Radiology: Ultrasound, CT, MRI
- Microbiology/Virology
- Immunology: PBC/PSC
- Histology
- Breath test: Bacterial overgrowth
