Plasma citrate levels as a potential biomarker for glaucoma.

PURPOSE: To determine the possibility of plasma citrate as a biomarker in patients with glaucoma. METHODS: Twenty-one consecutive Caucasian patients with glaucoma and 21 sex- and age-matched controls were investigated. Plasma citrate, plasma creatinine, urine citrate, and urine creatinine were analyzed by ion chromatography. Mean (±standard deviation) concentrations and the calculated fractional citrate excretions were compared using the Mann-Whitney test. Sensitivity and specificity to detect glaucoma using plasma citrate levels were calculated. RESULTS: The mean plasma citrate (104.8±23.2 vs. 128.2±31.1 µmol/L; P=0.01) concentrations were significantly lower among the patients with glaucoma, whereas the mean urine citrate concentrations (1.7±0.9 vs. 2.8±1.9 µmol/L; P=0.07) were slightly lower. Mean plasma and mean urine creatinine concentrations showed no significant differences (plasma creatinine: 63.0±16.7 vs. 63.4±15.5 µmol/L; P=0.72; urine creatinine: 9.6±5.1 vs. 11.5±8.4 µmol/L; P=0.67). The calculated fractional citrate excretions were also not different with 12.1% versus 13.6% (P=0.37). Setting the cut-off limit at 110 µmol/L, the plasma citrate level evaluation would have a sensitivity of 66.7% and a specificity of 71.4% to detect glaucoma. CONCLUSION: In this masked study, plasma citrate levels were significantly decreased in Caucasian patients with glaucoma giving the possibility to use them eventually as a biomarker. The kidney function was normal in both groups, leaving the etiology of this hypocitraemia yet unexplained.

Retinal vascular diameter in young subjects with a vasospastic propensity.

PURPOSE: Retinal vascular diameters have recently been shown not to be related to an increased risk of open-angle glaucoma. Because vasospastic propensity has been suggested to represent a risk factor for various ocular diseases, especially glaucoma, the steady-state retinal vascular diameter in subjects with a propensity for systemic vascular dysregulation was compared with a group of age-matched gender-matched controls. METHODS: Thirty healthy non-smoking individuals [female/male 26/4; mean +/- SD age 22.8+/-3.4 (range 18-31) years] were enrolled into the study. Subjects were classified as having vasospasm (15 subjects) if they related a clear history of frequently cold hands and as healthy subjects (15 subjects) if they denied such a history. Vasospastic propensity or the absence of it had to be confirmed by nail-fold capillaroscopy. Vascular diameter of retinal vessels was measured repeatedly on two days with the retinal vessel analyser and corrected for perfusion pressure, age, and refraction. RESULTS: Neither retinal arteriole diameter (P=0.30) or retinal venule diameter (P=0.49), nor retinal arteriole-to-venule ratio (P=0.96), differed between the two experimental groups. CONCLUSIONS: Although vasospastic propensity has been suggested to represent a risk factor in various ocular diseases, the steady-state retinal vessel diameters are not altered in healthy vasospastic subjects. It is probable that the steady-state retinal vessel diameters are no adequate risk indicators for the haemodynamic risk in diseases such as glaucoma.