Serum concentrations of ionized calcium reflect renal function in patients with sarcoidosis.
OBJECTIVE
Decrease in renal function was investigated in relation to altered metabolism of calcium in patients with sarcoidosis.


METHODS
Fifty consecutive patients with pulmonary sarcoidosis (23 men and 27 women, 47 +/- 15 years as mean +/- SD) were studied on a daily diet consisting of 500 mg of calcium and 1000 mg of phosphorus. Renal functions were evaluated with Z scores of creatinine clearance (Ccr).


RESULTS
Decreased renal function (Ccr Z score < -1) was detected in 13 out of 50 sarcoidosis patients (26.0%). In seven patients (14.0%) Ccr Z scores were less than -2; relative risk (RR) and 95% confidence interval (95% CI) were 13.9 and 2.97 to 64.7, respectively. Ccr Z score correlated most significantly with serum concentration of ionized calcium (sCa2+) (r = -0.574, 95% CI, -0.735 to -0.352, p < 0.0001). A stepwise regression analysis adjusting for observation time, serum concentration of calcium and 1,25-Dihydroxyvitamin D, urinary excretion of calcium, and urinary calcium crystals showed that sCa2+, together with angiotensin-converting enzyme activity in serum, was the most contributory variable to decrease in renal function in sarcoidosis patients (R2 = 0.391, p < 0.0001). A cutoff value of sCa2, 1.30 mmol/L obtained with a discriminant analysis showed 69.2% of sensitivity and 89.2% of specificity for decreased renal function.


CONCLUSIONS
We reported increased prevalence of decreased renal function among sarcoidosis patients. sCa2+ was a significant index that reflected the alteration of renal function.
Hamada
Kunio
K
Department of Respiratory Medicine, Graduate School of Medicine, Kyoto University, Japan. hamachan@kuhp.kyoto-u.ac.jp
Nagai
Sonoko
S
Shigematsu
Michio
M
Nagao
Taishi
T
Hayaschi
Michio
M
Tsutsumi
Takeo
T
Izumi
Takateru
T
D002117:Calcitriol / Q000097:blood; D002118:Calcium / Q000097:blood*; D005260:Female; D006801:Humans; D007668:Kidney / Q000503:physiopathology*; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012307:Risk Factors; D017565:Sarcoidosis, Pulmonary / Q000097:blood / Q000503:physiopathology*; D012680:Sensitivity and Specificity
D002117:Calcitriol; D002118:Calcium