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
Eva Nilsson a,), Henrik von Euler b, Jaak Berendson a, Anders Thorne cIngemar Naslund d, Anne-Sofie Lagerstedt b, Kristina Narfstrom b, Jerker M. Olsson ea Department of Chemical Engineering and Technology, Applied Electrochemistry, Royal Institute of Technology ( b Department of Small Animal Clinical Sciences, Swedish Uni Õ ersity of Agricultural Sciences ( c Department of Surgery, Hu
Hike Description Possum Gorge Overview: This section lies between the Soddy Creek Gorge Section and the Rock Creek Gorge Section of the Cumberland Trail. Beginning at its southern terminus off Heiss Mountain Road, the trail descends into the gorge of Big Possum Creek, climbs out of the gorge to the top of Hughes Ridge, and descends into the gorge of Little Possum Creek, then climbs again t
Dr Johan Conradie