Aim: To document the numbers and characteristics of New Zealand patients commencing renal replacement therapy because of end-stage kidney disease attributed to lithium treatment, and to calculate incidence rates.
Method: Data on such patients were provided by the Australia and New Zealand Dialysis and Transplant Registry from the start of the Registry in 1977 until 2013. Numbers of patients prescribed lithium in the community were provided by the Ministry of Health for 2009-2013; earlier years had fewer than 96% of prescriptions for lithium linked to individuals by their unique National Health Index number. Time trends were analysed by linear, logistic and Poisson regression. Incidence rates were also calculated for five-year periods.
Results: Thirty-five new patients were located with 'lithium toxicity' as their primary renal disease, starting the year after 'lithium toxicity' was included in the standard list (1995). A broader search for lithium within 'other' causes and 'other' comorbidities did not yield further patients. The mean age at the start of renal replacement therapy was 61.1 years (SD 9.2). Twenty-five patients were female. For 1996 onwards, new patient numbers increased on average by 8% per year (95% CI 1 to 15%) and incidence rates increased by 7% per year (95% CI 0 to 14%), an approximate doubling per decade. Form 2007-2011, the average annual incidence per million population was 0.74 (95% CI 0.43 to 1.21) for New Zealand, similar to that reported elsewhere: 0.78 (95% CI 0.67 to 0.90) for Australia and 0.91 (95% CI 0.50 to 1.52) for southern Sweden. Prescription rates across the three countries were also similar. In New Zealand between 2009 and 2013, over 7,500 patients were prescribed lithium each year.
Conclusion: Dosing and monitoring of patients prescribed lithium should follow guidelines, not only to avoid future psychiatric episodes and acute toxicity but also because such adherence may reduce uncommon but serious outcomes of long-term treatment such as end-stage kidney disease.