Data collection process
Data were extracted independently by one author (RJM) using a standard form. This included: author, year of publication, class of diuretic(s) and dose used, protocol (including presence of background therapy and whether placebo controlled), sample size, average age, sex distribution, ethnicity (if available) and prevalence of diabetes (if available). For the outcome measurements, mean (± standard deviation/standard error) of values for BP and aldosterone before and during diuretic (and before and during placebo treatment in placebo-controlled studies) and the difference between values on and before treatment. Where available, the difference in renin, serum potassium and systolic blood pressure (SBP) were extracted. If standard deviations were not reported these were calculated from standard errors, P-values or from confidence intervals. The duration of diuretic treatment at the time of measurement was also recorded. Where only graphical reports of measurements were available, an estimation from the graph was taken if it was judged to be accurate to within 10%. Units of aldosterone were converted to pmol/L for analysis if other units were used.