Plasma aluminium: a redundant test for patients on dialysis?

Aluminium toxicity as a cause of dementia, osteodystrophy and anaemia in patients receiving renal dialysis was first described in the 1970s and led to the regular monitoring of aluminium in plasma and dialysate water. However, aluminium phosphate binders have now been replaced by calcium-based binders or sevelamer and reverse osmosis (RO) water is used in the preparation of dialysate fluid. This has reduced the exposure of dialysis patients to aluminium and it is therefore opportune to review aluminium monitoring in patients undergoing regular renal dialysis.

Plasma and water aluminium results were audited over the period January 2000-January 2004, with results obtained from nine renal dialysis units in the UK. Patients with a plasma aluminium concentration in the toxic range (>3.7 micromol/L) were followed up by contacting the relevant consultant.

Plasma aluminium results were collected on 1626 patients over the four-year period (mean=0.47 micromol/L, median=0.3 micromol/L, range 0.07-30.26 micromol/L, n=5918). Forty-six patients had an aluminium concentration >3.7 micromol/L and nine were not retested. Only three patients had a repeat aluminium concentration >2.2 micromol/L, one being a result of desferrioxamine treatment, with no further clinical information available on the other two. All renal units are using RO water to prepare dialysate and aluminium-based phosphate binders are no longer prescribed. Only one of 212 RO water aluminium concentrations measured was >10 microg/L. Patients with clinical symptoms of overt aluminium toxicity were not identified in this population.

The role of aluminium monitoring in long-term renal dialysis patients needs re-evaluation. Regular monitoring of plasma aluminium may not be required, but should be considered in any patient showing signs or symptoms of aluminium toxicity or exposed to a contaminated water supply. It is more important that RO water supplies are maintained and monitored. Environmental aluminium as a source of sample contamination should be considered and eliminated during blood collection and sample processing.