Renal replacement therapy associated with lithium nephrotoxicity in Australia

To the Editor: Roxanas and colleagues1 overemphasise the relative risks of renal replacement therapy (RRT) with lithium treatment. Based on the most recent Australian defined daily dose statistics, about 1150 people per million population are taking lithium,2 and the incidence rate for RRT is ≤ 0.78 cases per million population per year.1 Therefore, in Australia, the risk of requiring RRT is < 1/1470, which is considerably lower than that in Sweden (1/187).1,3 The prevalence of patients taking lithium in Australia did not change from 1995 to 2010,2 meaning that the reported increase in patients requiring RRT over that period1 is more likely due to other factors, such as changes in diagnostic categorisations,1-3 or other medications.

Against this low risk of RRT, lithium, when compared with other pharmacological treatments, reduces the risk of suicide, self-harm and manic relapse in patients with major affective disorder.4 The number needed to treat to avoid one suicide is about 50.4 This means that for each person in whom RRT is avoided by cessation of lithium (< 1/1470 treated), up to 30 could be predicted to have committed suicide, and a larger number could be predicted to have a manic relapse or to self-harm.

The challenge is to predict the patients with lithium nephropathy who are likely to require RRT, given the lack of certainty of diagnosis or renal prognosis for such patients.1,3,4 Certainty about a progressive decline in renal function attributable to lithium may take some years in patients with substantial fluctuations in renal function over time,5 making informed consent to cease lithium particularly difficult because of the substantial psychiatric benefits.4