Interaction of neutrophil counts and folic acid treatment on new-onset proteinuria in hypertensive patients

We aimed to examine whether baseline neutrophil counts affected the risk of new-onset proteinuria in hypertensive patients, and, if so, whether folic acid treatment is particularly effective in proteinuria prevention in such a setting. A total of 8208 eligible participants without proteinuria at baseline were analysed from the renal substudy of the China Stroke Primary Prevention Trial. Participants were randomised to receive a double-blind daily treatment of 10 mg of enalapril and 0.8 mg of folic acid (n 4101) or 10 mg of enalapril only (n 4107). The primary outcome was new-onset proteinuria, defined as a urine dipstick reading of ≥1+ at the exit visit. The mean age of the participants was 59.5 (sd, 7.4) years, 3088 (37.6 %) of the participants were male. The median treatment duration was 4.4 years. In the enalapril-only group, a significantly higher risk of new-onset proteinuria was found among participants with higher neutrophil counts (quintile 5; ≥4.8 × 109/l, OR 1.44; 95 % CI 1.00, 2.06), compared with those in quintiles 1-4. For those with enalapril and folic acid treatment, compared with the enalapril-only group, the new-onset proteinuria risk was reduced from 5.2 to 2.8 % (OR 0.49; 95 % CI 0.29, 0.82) among participants with higher neutrophil counts (≥4.8 × 109/l), whereas there was no significant effect among those with neutrophil counts <4.8 × 109/l. In summary, among hypertensive patients, those with higher neutrophil counts had increased risk of new-onset proteinuria, and this risk was reduced by 51 % with folic acid treatment.