Estimated glomerular filtration rate and daily amount of urinary protein predict the clinical remission rate of tonsillectomy plus steroid pulse therapy for IgA nephropathy

BACKGROUND: This retrospective study was designed to estimate the clinical remission (CR) rate of tonsillectomy plus steroid pulse (TSP) therapy in patients with IgA nephropathy. METHODS: Based on 292 of 302 patients with IgA nephropathy treated at 11 Japanese hospitals, we constructed heat maps of the CR rate at 1 year after TSP with the estimated glomerular filtration rate (eGFR), grade of hematuria, pathological grade, number of years from diagnosis until TSP, and age at diagnosis on the vertical axis and the daily amount of urinary protein (urinary protein) on the horizontal axis. We compared subgroups usinge Student’s t test, the chi-square test with Yates correction, or Fisher’s exact probability test. RESULTS: The first heat map of eGFR and urinary protein showed that the CR rate was 71 % (CR vs. non-CR, 96 vs. 40) in patients with eGFR greater than 30 ml/min/1.73 m(2) and 0.3–1.09 g/day of urinary protein. However, the CR rate in patients with more than 1.50 g/day of urinary protein was approximately 30 %. The second heat map of grade of hematuria and urinary protein revealed that the CR rate is 72 % (CR vs. non-CR, 93 vs. 37) in patients with more than 1+ hematuria and 0.3–1.09 g/day of urinary protein; however, it was 28.6 % in patients with no hematuria. The third heat map of pathological grade and urinary protein demonstrated that the highest CR rate was 83 % (CR vs. non-CR, 52 vs. 11) in patients with pathological grade I or II disease and less than 1.09 g/day of urinary protein, as opposed to 22 % (CR vs. non-CR, 9 vs. 32) in patients with pathological grade III or IV disease and more than 2.0 g/day of urinary protein. The fourth heat map of the number of years from diagnosis until TSP and urinary protein revealed that the former did not influence the CR rate in patients with less than 1.09 g/day of urinary protein. However, in patients with more than 1.10 g/day of urinary protein, the CR rate of the subgroup with less than 6 years was 43 % (CR vs. non-CR; 23 vs. 54) compared to 23 % (CR vs. non-CR, 11 vs. 48; P = 0.01) in the subgroup with more than 6 years. The fifth heat map of age at diagnosis and urinary protein showed that the CR rate is approximately 72 % (CR vs. non-CR, 73 vs. 28) in patients older than 19 years at diagnosis with 0.3–1.09 g/day of urinary protein. CONCLUSIONS: The daily amount of urinary protein is an important predictor of the CR rate after TSP in IgA nephropathy patients. Heat maps are useful tools for predicting the CR rate associated with TSP.