Analytes Flashcards
What is prolactin?
A single-chain polypeptide hormone secreted by the anterior pituitary. MW 23kDa
Causes of hypernatraemia
Dehydration
Diabetes insipidus
Iatrogenic - saline infusion in renal failure
Salt ingestion
Sea water drowning
Causes of low IGF-1
Growth hormone deficiency
Malnutrition
GH insensitivity
Hypothyroidism
Diabetes mellitus
Renal failure
Cancer
DDx distal RTA
Autoimmune eg Sjogren syndrome, SLE< PBC
Drugs - amphotericin, lithium, toluene, analgesic nephropathy
Hereditary
Myeloma
DDx hyperchloraemic NAGMA
RTA
ureteric sigmoid anastomosis
carbonic anhydrase inhibitor
diarrhoea (with alkali loss)
Increased creatinine:urea on UEC
Obstructive uropathy
Low protein intake
In vitro artefacts causing hyperkalaemia
Haemolysis
Spherocytosis
Familial pseudohyperkalaemia
Severe thrombocytosis/leucocytosis
Delayed separation
EDTA contamination
Do slow spin sample/whole blood direct K
Causes of increased CSF bilirubin?
- SAH
- Meningitis
- Spontaneous intracranial hypotension
- High serum bilirubin (>20umol/L)
- Sample taken after previous traumatic tap
- High CSF total protein
- Increased WCC increases conversion of oxyhb to bili
- Hypercarotenaemia, iodine contamination, rifampicin may give the appearance of xanthochromia
Max absorbance of CSF oxyhaemoglobin and bilirubin?
Oxyhb - 410-418nm
Bili - 450-460nm (net bilirubin absorbance measured at 476nm to enable separation from oxyhb peak
Causes of false -ve CSF bilirubin for SAH
- Sample taken before 12 hours (oxyhb has not been converted to bilirubin yet)
- Sample taken after 10 days (pigments cleared from CSF)
- Sample exposed to light (bilirubin degraded)
- High oxyhb concentration (obscures bili peak by spectrophotometry)
- Turbidity of sample may obscure bili peak
Define methaemoglobin
Hemoglobin in which Ferrous (Fe2+) iron has been oxidized to Ferric (Fe 3+) iron. Methb is unable to carry oxygen.
Enzyme responsible for reducing metHb back to Hb?
Methaemoglobin reductase
Treatment for methaemoglobinaemia
Provide alternative reducing agent - methylene blue or ascorbic acid.
What are the 2 cardiac isozymes of LD?
1 and 2
What are the 2 skeletal muscle isozymes of LD?
4 and 5
What percentage of serum copper is bound to ceruloplasmin?
95%
Which enzyme is responsible for adding copper to the ceruloplasmin peptide chain? What is the clinical significance?
ATP7B. Mutations in this enzyme cause Wilson’s disease
True or false: most apoCp is released into the circulation
False. Most ceruloplasmin which is unbound to copper is degraded intracellularly. Although some makes it into the circulation, it has a short half life. Hence there are low concentrations of ceruloplasmin in Wilson’s disease
Ceruloplasmin method in your lab and interferences
Immunoturbidimetry
IgM monoclonal gammopathy (Waldenstrom’s)
What is immunoreactive trypsinogen?
A pancreatic enzyme that is increased in patients with CF
Causes of hypokalaemia
- Redistribution
- insulin
- alkalosis
- catecholamine/beta adrenergic excess
- pseudohypokalaemia
- hypothermia
- hypokalaemic periodic paralysis - Decreased intake eg starvation
- Loss of potassium rich body fluid
a) Renal
i) Acidosis- RTA 1 or 2
ii) Alkalosis - Mineralocorticoid excess
- Glucocorticoid excess
- Penicillins
- Diuretics
iii) Other - ATN, diuretic phase
- Amphotericin B toxicity
- Hypomagnesaemia
b) Extrarenal
i) GI - diarrhoea, fistula
- Vomiting/NG suction
ii) Skin - excessive sweating
- RTA 1 or 2
How to differentiate hypokalaemia due to renal vs GI loss?
Transtubular potassium gradient
24 hour urine K
Transtubular potassium gradient calculation?
(urine [K] x serum osm) / (serum [K] x urine osm)
Transtubular potassium gradient utility?
Indicator of mineralocorticoid effect on kidney
