Clinical background:
Patients in end-stage renal failure lose the ability to clear aluminium and are susceptible to aluminium toxicity. Aluminium present in dialysis water can expose dialysis patients to aluminium. If it is not removed by renal filtration, aluminium accumulates in the blood, where it binds to proteins such as albumin and is rapidly distributed throughout the body. Aluminium overload leads to accumulation in the brain and bones. Brain deposition has been implicated as a cause of dialysis dementia. In bone, aluminium replaces calcium at the mineralization front, disrupting normal osteoid formation.
It is mandatory that water used in haemodialysis is initially purified by reverse osmosis. The Renal Association has published guidelines recommending limits of various trace elements and pathogens in reverse osmosis water. It is suggested that aluminium content of purified water should be carried out every 3 months.
Specimen container paediatric:
Plastic Z10 tube
Navy blue-top serum trace element tube (available on request from Blood Sciences reception at both Freeman and RVI sites)
Specimen container adult:
Plastic Z10 tube
Navy blue-top serum trace element tube (available on request from Blood Sciences reception at both Freeman and RVI sites)
Minimum volume paediatric:
1 mL blood
1 mL water
Minimum volume adult:
1 mL blood
1 mL water
Special requirements:
Blood
Collect via cannula or dialysis line as 2nd or 3rd sample. Avoid dust (source of contamination).
Water
Allow water to run from source for 30 seconds prior to collecting sample. Avoid dust (source of contamination).
Sample stability:
Samples are stable for 6 weeks at 4°C or indefinitely when frozen.
Transport requirements:
Ambient temperature.
Interpretation:
Patients with renal insufficiency are susceptible to aluminium toxicity. There are several factors associated with dialysis procedures that may potentiate aluminium toxicity, including:
- aluminium in dialysis water
- dialysis processes that may not be efficient at eliminating aluminium
- use of oral phosphate-binder gels containing aluminium that is absorbed by the gut.
Reference ranges:
Serum:
(Supra-regional Assay Service cut-offs for serum aluminium in dialysis patients)
Aluminium (µmol/L)
No history of chronic renal failure (CRF)
Little risk of toxicity in CRF patients
Excessive accumulation; risk of toxicity in children
Cause for concern; risk of toxicity in children
High risk of toxicity in all patients
<0.4
<2.2
>2.2
>3.7
>7.4
Water:
(European Guidelines for Water / Dialysis fluid aluminium)
Aluminium (µmol/L)
Reverse osmosis water
Dialysis water/fluid
Drinking (tap) water
<0.4
<1.1
<7.4
Factors affecting result:
Failure to adhere to correct specimen collection procedures can cause abnormal results due to specimen (dust) contamination, which can lead to misinterpretation and misdiagnosis.
Other info:
Referral Laboratory: SAS Trace Element Laboratory, Surrey Research Park, 15 Frederick Sanger Road, Guildford, Surrey, GU2 7YD.