The Effectiveness of the Serum IgA Level in Diagnosing IgA Nephropathy

Kim, Myeong Sung; Shin, Gyu Tae; Yim, Hyun Ee; Kim, Seung Jung; Sheen, Seung Soo; Ma, Kyoung Ai; Cho, Nam Han; Choi, Young Il; Kim, Heung Soo; Kim, Do Hun

Abstract

BACKGROUND: Immunoglogulin A(IgA) nephropathy is the most common primary glomerular disease throughout the world. 30-50% of patients with IgA nephropathy(IgAN) have high serum IgA concentrations. However, we do not know if the degree of elevation in IgA level increases the likelihood of having IgAN. Neither do we know if the IgA level has any association with pathological findings of IgAN.
METHODS
We analyzed the relationships between IgAN and the levels of serum IgA which has been a routine part of the study in all patients with glomerulonephritis in our institution for the last 4 years. We reviewed 270 patients in whom the pathological diagnosis and the results of their IgA levels were both available.
RESULTS
Of 80 patients who were IgA nephropathy, 26 patients(32.5%) had higher than normal cut- off value of serum IgA(385 mg/dL). In contrast, 8.9 % of patients with other types of glomerulonephropathies showed the values above normal(p<0.0001). The risk ratio for an increase of one unit of the IgA level was 1.0025(logistic regression, p=0.0043), which was increased to 1.0079 when patients with low complement levels were excluded from the analysis. The data were also analyzed according to the immunofluorescence microscopic findings of IgAN, which were found to have no significant correlation with IgA concentrations.
CONCLUSION
The IgA level is a risk factor for IgAN throughout the whole range. However, it does not correlate with the IgA deposition in the renal tissue. We believe that this study will help understanding the interpretation of IgA levels in patients with IgAN.