Urinary excretion of β2-microglobulin as a prognostic marker in immunoglobulin A nephropathy.
OBJECTIVE
β2-microglobulin (β2-MG) is freely filtered at the glomerulus and subsequently reabsorbed and catabolized by proximal renal tubular cells. Urinary β2-MG is an early and sensitive biomarker of acute kidney injury; however, its utility as a biomarker of immunoglobulin A nephropathy (IgAN) is unclear.


METHODS
We included urinary β2-MG levels in the routine laboratory examination of all inpatients with biopsy-proven IgAN at our hospital from 2006 to 2010. We retrospectively analyzed the correlation between β2-MG levels and clinical parameters as a prognostic biomarker of IgAN.


RESULTS
A total of 51 patients (30 males, 21 females; mean age, 33.01 ± 12.73 years) with IgAN were included in this study. Initial demographic, clinical, and laboratory data for all patients are listed. The mean initial estimated glomerular filtration rate and 24-hour urine protein levels were 94.69 ± 34.78 mL/min/1.73 m(2) and 1.28 ± 1.75 g/day, respectively. The mean level of urinary β2-MG was 1.92 ± 7.38 µg/mg creatinine. There was a significant correlation between initial serum creatinine (iSCr), urine protein creatinine ratio (UPCR), and the level of β2-MG (r = 0.744, r = 0.667, p < 0.01). There was also a significant correlation between renal function tests and the level of urinary β2-MG (p < 0.01). Cox regression analysis showed that albumin, β2-MG, iSCr, and UPCR were significant predictors of disease progression in IgAN.


CONCLUSIONS
Urinary β2-MG levels showed a significant correlation with renal function and proteinuria in IgAN. Thus, we propose that urinary β2-MG may be an additional prognostic factor in patients with IgAN.
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Jae Ryung
JR
Shin
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Seung Min
SM
Kim
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Jung Sun
JS
Yoo
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Ji Yoon
JY
Park
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Seul Ki
SK
Kim
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Joo Hee
JH
Cho
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Kyung Hwan
KH
Jeong
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Tae Won
TW
Lee
Division of Nephrology, Department of Internal Medicine, Kyung Hee University School of Medicine, Seoul, Korea.
Chun Gyoo
CG
Ihm
D000328:Adult; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001706:Biopsy; D003404:Creatinine / Q000097:blood / Q000652:urine; D018450:Disease Progression; D005260:Female; D005919:Glomerular Filtration Rate; D005922:Glomerulonephritis, IGA / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology / Q000652:urine*; D006801:Humans; D007297:Inpatients; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011237:Predictive Value of Tests; D011379:Prognosis; D016016:Proportional Hazards Models; D011507:Proteinuria / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology / Q000652:urine*; D012307:Risk Factors; D055815:Young Adult; D001613:beta 2-Microglobulin / Q000652:urine*
D015415:Biomarkers; D001613:beta 2-Microglobulin; D003404:Creatinine
Glomerulonephritis, IGA; Prognostic factor; Urinary β2-microglobulin