Original Editor - John Mitchell
- 1 An Introduction To Pathology
- 2 Chemical Pathology
- 2.1 Water and sodium
- 2.2 Potassium
- 2.3 Renal Function Tests - Urea & creatinine
- 2.4 Enzymes
- 2.5 Thyroid diseases
- 2.6 Glucose:
- 2.7 Lactate
- 2.8 Albumin
- 2.9 C-reactive protein
- 2.10 Uric acid
- 2.11 Tumour Markers
- 3 Immunology
- 3.1 Anti-nuclear antibody (ANA)
- 3.2 Anti-mitochondrial antibodies (AMA)
- 3.3 Anti-smooth muscle antibodies (ASMA)
- 3.4 Rheumatoid factor (RF)
- 3.5 Anti-Reticulin Antibodies.
- 3.6 Anti-acetylcholine receptor antibody
- 3.7 Anti-cardiolipin antibody
- 3.8 Anti-dsDNA antibody
- 3.9 Anti-ENA (extractable nuclear antigen) Antibody
- 3.10 Anti-Intrinsic Factor antibody
- 3.11 Anti-neutrophil cytoplasmic antibody (ANCA)
- 3.12 Anti-thyroid antibody
- 4 Haematology
- 5 References
An Introduction To Pathology
Different clinical areas which can be tested:
- Haematology (blood bank)
Use of Pathology Tests
Differential Diagnosis: to confirm or refute
Prognosis: risk factors
Monitoring: progress & treatment
Screening: subclinical presence of pathology
Is it normal?
Is it different?
Is it consistent with clinical findings?
Factors affecting results
- Age and stage of development
- Nutritional state
- Other medical intervention
NB reference ranges apply to adults only and are laboratory-specific and not applicable to every lab result
Water and sodium
Na: 135-145 mmol/l
↓Na - Hyponatremia (from skin, kidneys, gut) – weakness, postural hypotension, syncope, wt loss, cv changes, decreased skin turgor.
↑Na - Hypernatremia (incr. intake, decr. Excretion) – oedema, pulmonary oedema, HT, effusions
K: 3.4-5.2 mmol/l
↓K- Hypokalemia (alkalosis, RF, D&V,diuretics) – Weakness, ileus, hypotonia, confusion, depression, arrhythmias, alkalosis.
↑K- Hyperkalemia (catabolism, acidosis, RF) – Cardiac arrest with VF.
Renal Function Tests - Urea & creatinine
U: 2.5-6.5 mmol/l Cr: 60-120μmol/l
Both should rise together in renal failure. Creat is the more accurate measurement, urea is affected more by diet and dehydration.
Creatinine Clearance Crcl: 100-120mls/min
Measures glomerular filtration rate and permeability
- Have a specific time window of elevation
- Temperature specific
alk: 30-120 IU/l
- ↑ - Pagets, osteomalacia, bone tumours, healing #, osteomyelitis.
Cholestasis, cirrhosis, hepatitis, liver tumour.
Alt/GPT: <40 IU/l
- ↑ - Acute and chronic hepatitis, liver necrosis, tissue hypoxaemia and crush injuries, cholestasis & other liver diseases.
Creatine kinase CK: ♂40-215 ♀40-185 IU/l
- ↑ - MI, rhabdomyolisis, Sk. Muscle trauma, MD, severe exercise
Enzymes and MIs
- -Troponin T (Trop T) rises within hours & remains elevated for days. Results reported as neg, pos or some myocardial damage.
- At 3hrs, 25% of MIs have raised CKs
- At 6hrs, 72% “ “ “ “ “
- At 9hrs, 97% “ “ “ “ “
Gamma glutamyl tranferase
γGT/GTP: ♂<65 ♀<55 IU/l
- ↑ Liver disease esp. Cholestasis, alcoholic liver disease, cirrhosis, hepatitis
Amy: <100 IU/l
- ↑ Acute pancreatitis
other abdo disorders, RF
Hyperthyroidism (Graves disease, multinodular goiter, adenoma) – weight loss, sweating, palpitation, angina, tremor, diarrhea, muscle weakness, goiter, eyelid retraction.
Hypothyroidism (Hashimotos disease, post surgery, congenital, secondary to pituitary/hypothalamic disease)
- lethargy, cold intolerance, dry coarse skin & hair, hoarseness, wt gain, slow reflexes & muscle relaxation. Others including: anaemia, psychosis, constipation bradycardia, CTS, infertility.
Thyroid Function Testing:
>15mU/l - 1° hypothyroidism
0.3-5mU/l - euthyroid (normal)
<0.3mU/l - Further investigations!
Interpretation complicated by:
-Many medications, hormones
-Any acute illness – “sick euthyroidism” all thyroid tests are low.
-Recovery – TSH raised.
Fasting 3-5.5 mmol/l
>7.8 – diagnostic of DM
5.5-7.8 – impaired glucose tolerance
Thirst, polyuria, dehydration, hypotension, tachycardia, drowsiness.
(and for IDDM, DKA) ketosis, hyperventilation, vomiting.
Tiredness, confusion, detachment, ataxia, blurred vision, dizziness, paraesthesia, hemiparesis, convulsions, coma
↑ mainly due to tissue hypoxia (decreased perfusion or decr. PO2)
alb: 36-50 g/l
- Maintains oncotic pressure (keeps fluid in vessels)
- Transports small drugs, calcium & hormones
- ↓ (Many causes incl. malnutrition, liver disease, overhydration, incr. cap. Permeability, protein-losing states, burns, haemorrhage, general catabolism-sepsis, fever, malignancy, trauma)
- Symptoms – edema! (Unresponsive to diuretics or elevation)
An ‘acute phase’ protein
-Monitoring infections (>100, more likely to be bacterial)
-Distinguishing between AI diseases and active infection
-Monitoring RA Rx
-Checking for post-op infection
More sensitive than ESR
Incr. production/decr. Excretion → gout (exquisite pain and inflammation often in 1st MTP joint)
>0.54 mM → 50% chance of developing gout
- Chemicals related to the presence/progress of a tumour
- Either secreted by tumours or cell surface antigens
- Of greater prognostic than diagnostic use, should always be interpreted in the light of clinical and other diagnostic findings.
- Monitoring/detection of colorectal, gastric, breast, bronchial, bronchial and some ovarian cancers.
- Modestly elevated levels in a variety of non-malignancies
AFP <9 KU/l
- Monitoring/detecting liver cancers, testicular cancer.
- Also raised in pregnancy, hepatic regeneration.
Human Chorionic Gonadotrophin
- Diagnosis and monitoring of choriocarcinoma, also testicular tumours.
- Also used to detect ectopic pregnancies.
Prosate Specific Antigen (PSA)
- Monitoring/detecting prostate cancer
- Maybe raised in benign prostatic hypertrophy
- 96% of patients with ovarian cancer have raised levels
- Elevated in patients with pancreatic tumours
- Elevated in 70% of patients with metastatic breast cancer. A good marker for monitoring Rx.
- Elevated in 98% of patients with myeloma (and other malignancies of B-cells.
- Myeloma is a haematological malignancy the symptoms of which are anaemia, bone pain (esp LBP) and pathological #s.
Anti-nuclear antibody (ANA)
Associated with “connective tissue disease” positive in 95% of SLE, also found in JCA, Sjogren’s syndrome, fibrosing alveolitis
Anti-mitochondrial antibodies (AMA)
positive in >95% of primary biliary cirrhosis.
Anti-smooth muscle antibodies (ASMA)
Positive in 50-70% of autoimmune “lupoid” hepatitis.
Rheumatoid factor (RF)
(anti-IgG antibodies) Positive in 70% of RA (but lots of false positives). Should only be used to screen, NOT monitor, (use C-RP instead)
-Present in Coeliac disease. Also Crohn's and UC.
Anti-acetylcholine receptor antibody
Positive in 80-95% MG
Anti-phospholipid syndrome (recurrent abortion, thromboses, thrombocytopaenia)
Strongly suggestive of SLE
Anti-ENA (extractable nuclear antigen) Antibody
Used to classify connective tissue diseases
Anti-Intrinsic Factor antibody
Positive in 70% of pernicious anaemia
Anti-neutrophil cytoplasmic antibody (ANCA)
Granulomatosis with Polyangiitis, Microscopic polyangiitis
95% positive in Hashimotos thyroiditis
90% positive in primary myxoedema
18% positive in Graves disease
Coagulation studies -Measure the clotting mechanisms, for diagnosis and extent of disorder.
- DVT, PE
- MI, Unstable Angina
- >30 mins GA with post-op bed rest.
- High risk patients.
Pregnancy - Relevant side effects
Monitoring of Heparin
Low dose subcut. –
no laboratory control required
Continuous iv infusion or full dose subcut. –
APTT (activated partial thromboplastin time) should
be between 50-75 seconds. Caution with high values
(>100) re spontaneous bleeding.
- Patients require close monitoring of INR (International Normalized Ratio).
- Target INR ranges are 2-3 for moderate anticoagulation and 3-4.5 for more intensive therapy.
- These doses may fluctuate with no clinical significance.
Warfarin requirements may be dramatically changed by:
- Change in diet
- Change in other medication
International normalized ratio (INR)
>10 Life threatening haemorrhage can occur.
>4.5 Caution re spontaneous bleeding
-Always be wary of patients with mild haemorrhage such as haematuria or epistaxis (nosebleed).
Full Blood Count (FBC)
Red blood cell count (RBC)
↓anaemias, Hodgkins disease, myeloma, leukaemia, haemorrhage, SLE, rheumatic fever and chronic infection.
↑polycythaemia, renal disorders, decr. plasma vol: (severe burns, shock, vomiting)
↓anaemia, hyperthyroidism, liver/kidney disease, many CAs (especially haematological) SLE
↑haemoconcentration disorders: burns, polycythaemia, COPD, CCF.
<5 can lead to MI
>20 can lead to clogging of capillaries.
White blood cell count (WBC)
A useful guide to the severity of a disease process
Neutrophilia(↑) bacterial infections, gout, uraemia, poisoning, haemorrhage, haemolysis, necrosis.
Neutropaenia(↓) bacterial infections (poor prognosis) viral infections, certain anaemias, blood cancers, anaphylactic shock.
Eosinophilia(↑) Allergic reactions, parasitic diseases, certain blood cancers, skin infections, immunodeficiency disorders.
-Other variations occur in the specific white blood cell differential count with conditions such as: anaemias, blood cancers, infections, and certain inflammatory disorders.
Thrombocytosis(↑) malignancies, polycythaemia, RA & other inflammatory diseases, acute infections,
Thrombocytopaenia(↓) toxic affects of drugs, esp. chemotherapy, allergies, anaemias, viral infections, post transfusion, ITP.
Caution with low values re spontaneous bleeding, and bruising.