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Dr Johan Conradie
Western Diagnostic Pathology, Perth, Western Australia
A GP requested a home visit for some “follow up 1. What pre-analytical factors may alter the bloods” on a 68 year-old female patient being treated for a urinary tract infection. Urea, electrolytes and 2. What clinical factors may cause raised creatinine were requested with clinical notes stating ‘Follow-up’. You are shown the following results for 3. What would your approach be with these results? Reference Interval
Question 2
There are various drugs and medical conditions that
Question 1
may result in a raised potassium concentration: Various factors influence potassium during blood Potassium-sparing diuretics: Spironolactone, collection, handling and processing (pre-analytical Prostaglandin inhibitors (NSAIDS): ibuprofen, 1) “Fist pumping” usually employed to make veins ACE-inhibitors, AG II blockers, Digoxin.
more pronounced, this technique may increase Clinical conditions leading to hyperkalaemia include: 2) Incorrect order of draw: EDTA tubes contain Haemolysis, leucocytosis and thrombocytosis enough potassium to grossly distort potassium levels due to carryover. The usual correct order of draw (according to standard tube stopper colour) Renal failure (acute/chronic), diabetes mellitus is: white (sterile), blue (citrate), Red/yellow (syndrome of hyporeninaemic hypoaldosteronism (serum), Green (heparin), Purple (EDTA) and or due to insulin deficiency/diabetic ketoacidosis, Grey (Potassium Oxalate and Sodium Fluoride/ mineralocorticoid deficient syndromes (including Addison’s disease or adrenal C21-hydroxylase 3) Haemolysis may cause a significant increase as RBCs contain on average 160mmol/L vs. 4.2 Question 3
4) Delayed separation of serum from RBC or a) Is this result real (i.e. clinically relevant) or is it 5) Inadequate/incorrect centrifugation: Spinning for too long or too short or incorrect spinning speed; gravitational-forces may be inadequate to separate the platelets from serum, causing potassium leaking from them. Red cell ‘streaking’ Are there any previous results to compare to through the gel may cause potassium leaking into the serum compartment if serum is stored on the gel. Inappropriate high G-force may cause check haemolysis index if available, the date and time of collection, were there any 6) Re-centrifugation of SST (gel separator) has been delays in separation, is there any clinical found to increase potassium levels by up to 47%.
information on the request form that may 7) IV contamination: drawing from the same arm indicate a clinical reason, check for EDTA The Clinical Biochemist Newsletter June 2010 Was the gel integrity maintained? (i.e. any Pre-analytically: The sample was collected and
analysed within an acceptable time period. On inspection the serum appeared clear with no signs of transported? Was it collected by a trained haemolysis. EDTA contamination was excluded. On close examination it appeared the gel plug failed to completely seal, leaving a small corridor open between After going through this process one should have a clear the tube and gel-edge. As this patient had previous idea of whether this result is real or not. If uncertainty evidence of borderline raised potassium levels as still prevails, this should be a good time to discuss the well as a recent (confirmed) critical hyperkalaemia concentration (see 20/01) the attending GP was contacted and it was decided to hospitalise the patient for further This particular case was interesting, as this was a mixed assessment and treatment if needed. The hyperkalaemia was confirmed (6.1mmol/L); it is thought that some of the potassium from the original result of 7.5mmol/L might have been due to potassium leakage.
(mmol/L) (mmol/L)
(mmol/L) (µmol/L)
After reviewing and adjusting the patient’s treatment regime, the hyperkalaemia resolved with some References
1. Effects of Preanalytical Variables on Clinical Laboratory Tests, (3rd ed) Donald S. Young, 2. Clinical Disorders of Fluid and Electrolyte Metabolism, (5th ed). Robert G. Narins; ed. Clinically: According to the GP the patient had Stage 3
renal impairment and was being treated for hypertension (loop diuretics and ACE-inhibitor), chronic back pain Complicating the Treatment of Hypertension. Dr Damon Bell
Royal Perth Hospital, Western Australia
A 79 year-old previously very well woman was Reference Interval
admitted to hospital with increasing confusion and inability to mobilise. She underwent a minor surgical procedure four days before this presentation and has had severe nausea since. She had not vomited, but could not even look at food. She had been very diligent with maintaining her water intake as instructed by the surgical staff after the procedure. She was taking bendrofluazide 2.5 mg daily, started 10 days before admission by her GP for mild hypertension noted on the 1. What causes of the hyponatraemia would you pre-surgery visit. She suffered a seizure in the ED and was subsequently admitted to the ICU where she was 2. What further investigations would be helpful? 3. What is the likely cause of the severe Reference Interval
4. What are the complications of hyponatraemia? The Clinical Biochemist Newsletter June 2010

Source: http://oldsite.aacb.asn.au/files/File/omniscience/June%20CBN%202010%20Case%204.pdf