Clinical significance of fractional magnesium excretion (FEMg) as a predictor of interstitial nephropathy and its correlation with conventional parameters.
BACKGROUND
Elevated urine Mg excretion and its correlation with histological damage in tubulo-interstitial nephropathy (TIN) were reported. Here we investigated the clinical significance of the fractional excretion of Mg (FEMg) for the prediction of TIN.


METHODS
We enrolled and assessed 94 adult patients with various renal diseases diagnosed principally by renal biopsy.


RESULTS
Our stratified analysis based on the value of the conventional TIN parameter N-acetylglucosaminidase (NAG) excretion showed that the high-NAG index group (more than median value of NAG-to-Cr ratio, n = 47) demonstrated significantly high FEMg values (p = 0.017). A univariate analysis revealed a significant correlation between the FEMg and the NAG index (R = 0.60) but not for other parameters. A multivariate regression analysis confirmed the significance of the FEMg as an effective predictor of the NAG index. The FEMg showed a significant correlation with the estimated glomerular filtration rate (eGFR) in the patients with eGFR ≤ 30 mL/min. The correlation of FEMg with the NAG index was not observed in the primary glomerulonephritis patients but was apparent in the patients with hypertensive nephrosclerosis or interstitial nephritis.


CONCLUSIONS
Our findings may indicate that the combination of the FEMg and the NAG index can provide a specific, sensitive assessment for TIN in patients without renal insufficiency.
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Chie
C
Noiri
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Taisuke
T
Shimizu
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.|Ishikawa Kinenkai Kawagoe Ekimae Clinic, Wakita-honmachi16-23, Kawagoe, Saitama, 350-1123, Japan.
Kaori
K
Takayanagi
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Yosuke
Y
Tayama
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Takatsugu
T
Iwashita
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Shimpei
S
Okazaki
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Minoru
M
Hatano
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Osamu
O
Matsumura
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Hitoshi
H
Kato
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Akihiko
A
Matsuda
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan.
Tetsuya
T
Mitarai
Department of Nephrology and Hypertension, Saitama Medical Center, Saitama Medical University, Kamoda 1981, Kawagoe, Saitama, 350-8550, Japan. hase2126@saitama-med.ac.jp.
Hajime
H
Hasegawa
D000118:Acetylglucosaminidase / Q000652:urine; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008274:Magnesium / Q000652:urine*; D008297:Male; D008875:Middle Aged; D009395:Nephritis, Interstitial / Q000473:pathology / Q000652:urine*; D011237:Predictive Value of Tests; D055815:Young Adult; D001613:beta 2-Microglobulin / Q000652:urine
D001613:beta 2-Microglobulin; D000118:Acetylglucosaminidase; D008274:Magnesium
FEMg; Hypermagnesiuria; N-acetylglucosaminidase; Tubulo-interstitial nephropathy; β2-microglobulin