IgA nephritic patients of Pacific Asian origin with increased risk of progression to end-stage renal disease
Authors: Keng-Thye Woo, Marjorie W.Y. Foo, H.Lina Choong, Han Khim Tan, Kok-Seng Wong, Choong-Meng Chan
Journal: Kidney International (2014)

To the Editor: We read with great interest the above article1.Barbour S.J. Cattran D.C. Kim S.J. et al.Individuals of Pacific Asian origin with IgA nephropathy have an increased risk of progression to end-stage renal disease.Kidney Int. 2013; 84: 1017-1024Abstract Full Text Full Text PDF PubMed Scopus (93) Google Scholar in which the authors compared two groups of patients, a group of 202 Canadian patients of Pacific Asian origin and a group of 467 Canadian patients (mainly Caucasians), over a follow-up period of 46 months. These patients were recruited through the Toronto GN Registry and were registered from 1974 to 2012. The authors found that by univariate analysis the risk of end-stage renal disease (ESRD) was similar in the two groups, but that by multivariate analysis the risk of ESRD was significantly higher in the Pacific Asian group. This was supported by a significant 1.62ml/min/year of faster estimated glomerular filtration rate (eGFR) decline in the Pacific Asian group. However, we note that in Table 1, 73.3% of Pacific Asian patients versus 45.3% of Caucasian patients were on angiotensin-converting enzyme inhibitors/angiotensin receptor blockers (ACEI/ARB) (P<0.001). Similarly, there were more Pacific Asian patients on steroids compared with Caucasians (23.8% versus 15.9%, P<0.02). Also, more Pacific Asian patients were on immunosuppressants compared with Caucasians (25.7% versus 19.3%, P<0.07). These two groups of patients in Canada would presumably have received standard medical care, and their medication would have been prescribed on the basis of clinical indications, such as proteinuria and eGFR. Considering the larger number of patients in the Pacific Asian group who required treatment, it would suggest that this group probably had more severe disease. Hence, it would not be surprising that the Pacific Asian group would have a more rapid decline of renal function and progression to ESRD. We believe that these two groups are not comparable on the basis of patient numbers and on the proportion of patients who are on treatment in the two groups. It may therefore be premature to attribute the more rapid decline in eGFR in the Asian patients to a ‘racial effect’. D’Amico,2.D’Amico G. Natural history of idiopathic IgA nephropathy and factors predictive of disease outcome.Seminars Nephrol. 2004; 24: 179-196Abstract Full Text Full Text PDF PubMed Scopus (372) Google Scholar in a worldwide review of the actual renal survival at 10 years for patients with IgA nephritis, reported 87% patient survival in Australia, 85% in Europe, 81% in Germany, 85% in Italy, 80% in Japan, 83% in the United Kingdom, 78% in the United States of America, and 82% in Singapore. Li et al.3.Li P.K.T. Kai K.L.H. Szeto C.C. et al.Prognostic indicators of IgA nephropathy in the Chinese—clinical and pathological perspectives.Nephrol Dialysis Transpl. 2001; 17: 64-67Crossref Scopus (144) Google Scholar reported a 10-year survival of 82% among the Chinese in Hong Kong. There was not much variation in renal survival for IgA nephritics worldwide. With regard to the rate of eGFR decline, Prakesh et al.4.Prakash S. Kanjanabuch T. Austin P.C. et al.Continental vatiations in IgA nephropathy among Asians.Clin Nephrol. 2008; 70: 377-384Crossref PubMed Google Scholar compared two cohorts of Asian patients with IgA nephritis from two continents in a retrospective study. A cohort of 76 patients from Thailand (1994–2005) was compared with a cohort of 152 Asian Canadian patients (1975–2006) who were also from the Toronto GN Registry. The adjusted rate of eGFR decline in the Thai patients was -0.8ml/min/year compared with -3.35ml/min/year in the Asian Canadian patients. The Asian Canadian patients were not treated with ACEI/ARB as their study period predated the introduction of ACEI/ARB in Canada. However, the Thai patients received ACEI/ARB and steroids, which may explain the slower rate of eGFR decline, although the authors attribute this difference to what they consider the ‘continental effect’ causing the variation in the rate of eGFR decline in these two groups of Asian patients. This study demonstrates that not all Asians with IgA nephritis have an increased risk of progression to ESRD. It may be a ‘continental effect’, as suggested by the authors, but the ‘racial effect’ appears nonexistent.