Lists

Question 1

Causes of an increased CK

Answer 1

Analytical - macro CK
Non-exertional (STEEMi)
- Statins and other drugs
- Traumatic/ compressive
- Electrolyte disturbance (hypokalaemia, hypophosphataemia)
- Endocrine (hypothyroidism, acromegaly, thyrotoxic periodic paralysis etc)
- Myopathies (inflammatory- dermatomyositis, polymyositis etc)
Exertional
- Normal muscle: seizures, extreme exercise, environmental heat illness, sickle cell trait, hyperkinetic states
- Abnormal muscle: metabolic and mitochondrial myopathies, malignant hyperthermia/neuroleptic malignant syndrome, dystrophinopathies (muscular dystrophies)

Question 2

Causes of a hepatitic pattern of abnormal LFTs

Answer 2

Viral (HBV, HCV, EBV, CMV)
Alcohol
NAFLD
Medications (NSAIDs, paracetamol, AEDs)
Haemochromatosis
Alpha-1-antitrypsin deficiency
Autoimmune hepatitis
PBC
PSC
Ischaemic

Question 3

Causes of a falsely low HbA1c

Answer 3

Pathological:
Increased red cell turnover eg haemolytic anaemia, recent red cell transfusion, recent iron infusion
Chronic liver disease
Pharmacological:
Dapsone
Hydroxyurea
Antivirals (ribavirin, HAART)
Preanalytical/analytical:
Hb variant interference (HPLC/CZE)
Hypertriglyceridaemia (immunoassay)
Short EDTA sample (excessive calcium chelation) (Vitros)

Question 4

Causes of a falsely increased HbA1c

Answer 4

Pathological:
Iron deficiency with or without anaemia
CKD
B12 deficiency
Alcohol
Pharmacological:
Aspirin
Opiates
Preanalytic/analytical:
Hb variant (HPLC/CZE)
Heterophile antibody

Question 5

Causes of hypophosphataemia

Answer 5

Intracellular shift: refeeding, IV glucose/insulin, DKA, respiratory alkalosis (complex mech involving glycolysis and increased phosphorylation), burns, hungry bones
Lowered renal phosphate threshold: hyperparathyroidism, iron infusion, renal tubular defects (familial hypophosphataemia, Fanconi syndrome), oncogenic osteomalacia, alcoholism, burns
Decreased intestinal phosphate absorption: vomiting, diarrhoea, phosphate-binding antacids, malabsorption syndrome, vitamin D deficiency, alcoholism
Genetic: X-linked hypophosphataemic rickets, Dent disease
Drugs: Acetazolamide, bisphosphonates, diuretics, oestrogens, HIV therapy, salicylates, TKIs

Question 6

Causes of cholestatic LFTs

Answer 6

1. Intrahepatic - neoplastic (primary or metastatic), infiltrative (amyloidosis, leukaemias, lymphomas), PBC, granulomatous, post-transplant cholangiopathy, AIDS, TPN
2. Extrahepatic - gallstones, head of pancreas tumours, cholangiocarcinomas, biliary stricture (congenital biliary atresia), PSC
3. Cholestatic hepatitis - drugs eg oestrogens and anabolic steroids, viruses

Question 7

Metabolic myopathies associated with rhabdomyolysis

Answer 7

Disorders of lipid metabolism and glycogen storage disorders including McArdle’s disease.

Question 8

DDx methaemoglobinaemia

Answer 8

1. Drugs (most common cause) - dapsone, sulfamethoxazole, nitrates
2. Hereditary - types I, II, IV, HbM, unstable Hb, G6PD deficiency

Question 9

Causes of a low anion gap

Answer 9

1. High chloride, iodide, bromide
2. Decreased albumin
3. Increased cations (calcium, magnesium, lithium, proteins)