diagnostic techniques

Question 1

individual laboratory medicine specialties:

Answer 1

Clinical Biochemistry
- study of changes in the chemical composition of body fluids in the diagnosis and monitoring of disease processes.

Immunology
- study of the body’s immune system and its disorders.

Microbiology
- study of infection caused by bacteria, fungi, parasites and viruses; identification of the best treatment options for infection; and the monitoring of antibiotic resistance
- includes testing for how well a patient is responding to treatment of infection.

Haematology
- study of blood cells.

Histopathology / Cytopathology
- study of diseased tissue/cells.

Genetics
- study of DNA and its relation to genetically transmitted disorders.

Question 2

List the reasons for requesting laboratory investigations:

Answer 2

Screening - Detection of sub-clinical disease
e.g.
(Neonatal Screening for PKU / Cervical Smear for cervical cancer)

Diagnosis - Confirmation or rejection of clinical diagnosis
e.g.
(Measurement of urea and creatinine for? renal failure / Biopsy for? lung cancer)

Monitoring - Natural history or response to treatment
e.g.
(Measurement of CRP to see if an infection is resolving / Measuring CD4 and viral load for HIV monitoring)

Prognosis - Prediction of course or outcome of the disease
e.g.
(Tumour markers)

Question 3

point of care testing:

Answer 3

laboratory testing performed in the clinical setting by non-laboratory healthcare professionals.

The lab oversees POCT.

Advantages:

Improved turnaround time
(you can access an instant Troponin in A+E versus the extended vein-to-brain time of sending to the lab)

Potential for better monitoring of certain conditions

Smaller sample volumes

Less clinically invasive

In some out-patient settings, POCT results can be used to adjust patients’ medication resulting in less frequent clinic appointments

Question 4

disadvantages of post:

Answer 4

• Can often be expensive.
• Faster turnaround time may not affect discharge time (either from A+E/AMIA to a ward, or home),
  which often depends on other investigations/referrals.
• The reliability of POCT results (especially those undertaken on unregulated equipment) is often an issue.

the idea of a single drop of blood that tells you everything is amazing – but who looks after the precision and accuracy of the tests that you are undertaking?
Learning to do this is a massive, incredibly complex process which is undertaken by highly specialist scientists

• Monitoring quality control is tricky
  → Monitoring and storage of POCT reagents and QC material
  esp. in remote areas
• Hard to control for operator variability
  i.e. ensuring that all operators are trained to a high standard

Question 5

Describe common pre-analytical errors that can contribute to erroneous electrolyte results

Answer 5

[1] Inaccurate Point of Care (POC) glucose test compared to lab glucose test
i.e. CASE STUDY 3 - slide 52

[2] EDTA contamination
→ EDTA is an anticoagulant, that inhibits clotting by chelating Calcium and Magnesium.
→ causes high sodium, low calcium, and potentially a low ALP

Question 6

Why is it important to adhere to the laboratory sample acceptance policy?

Answer 6

To maintain sample integrity and prevent errors

Question 6

lab test in patient pathway:

Answer 6

Prevention and screening:

• Lipid profile: Assesses cholesterol levels for cardiovascular disease risk
• Fecal occult blood test: Screens for colorectal cancer.
• HbA1c: Screens for prediabetes and diabetes.
  Genetic testing: Identifies predispositions for conditions like BRCA mutations in breast cancer.

Diagnosis:

• Complete blood count (CBC): Diagnoses anaemia, infections, or leukaemia
• Troponin levels: Detects myocardial infarction.
• Serum creatinine and blood urea nitrogen (BUN): Diagnoses kidney dysfunction.
• Throat swab and culture: Confirms bacterial causes of pharyngitis.

Treatment planning:

• Antibiotic sensitivity testing: Determines the most effective treatment for bacterial infections.
• HER2 testing in breast cancer: Guides the use of targeted therapy like trastuzumab.
• Liver function tests (LFTs): Checks for suitability of certain medications that might be hepatotoxic.

Monitor and management:

• INR (International Normalized Ratio): Monitors blood-thinning therapy (e.g., warfarin).
• Thyroid-stimulating hormone (TSH): Monitors thyroid hormone replacement therapy.
• Viral load in HIV: Monitors the effectiveness of antiretroviral therapy.

Prognosis and follow-up:

• Tumor markers (e.g., CA-125): Monitors for recurrence of ovarian cancer.
• Erythrocyte sedimentation rate (ESR): Tracks inflammation in chronic conditions like rheumatoid arthritis.
• Prostate-specific antigen (PSA): Monitors for recurrence of prostate cancer.

Rehabilitation and long-term management:

• Electrolyte panels: Monitors heart failure or diuretic therapy effects.
• Liver function tests: Tracks chronic liver disease progression.
• Blood glucose: Manages long-term diabetes control.