Calcium oxalate supersaturation of the blood is associated with deposition of crystals in various tissues. We measured the serum levels of
oxalate,
citrate, calcium, and
magnesium to estimate their saturation in 112
hemodialysis patients without
primary hyperoxaluria and two boys with
primary hyperoxaluria. Serum levels of
oxalate and
citrate were determined by high-performance capillary electrophoresis, while
calcium and
magnesium were measured by ICP spectroscopy. The serum levels of
oxalate,
citrate, calcium, and
magnesium were 44.9+/-16.5, 138.1+/-54.9 micromol/l, 2.30+/-0.28, and 1.07+/-0.18 mmol/l, respectively, while the levels in patients with
primary hyperoxaluria were 83.9+/-34.3, 197.9+/-63.5 micromol/l, 2.53+/-0.15, and 1.14+/-0.34 mmol/l, respectively. Serum
calcium oxalate saturation (SS), as calculated by the Equil program, was significantly correlated with the serum
oxalate level. Most patients showed metastable supersaturation (1<SS<8.9), which was associated with a serum
oxalate level of more than 30 micromol/l. Serum saturation exceeded the formation product (SS=8.9) in some specimens from patients with type 1
primary hyperoxaluria. The serum
calcium oxalate saturation [SS(CaOx)] showed a significant positive correlation with the levels of
oxalate [Ox],
calcium [Ca], and
citrate [
Cit]: [SS(CaOx)]=-0.3562+34.634[Ox]+0.394[Ca]-0.483[Mg]+0.101[
Cit], (all mmol/l, r=0.9848, P<0.01). This formula is useful for estimating the saturation. In conclusion, the serum
oxalate level is a good
indicator of
calcium oxalate saturation and should be monitored accurately while keeping it lower in dialysis patients.