Table 1.
Demographic and medical characteristics of the patients.
Table 2.
Biological characteristics of the 67 patients.
Fig 1.
Urinary response to an acute acid load in patients with a normal acid-base status.
A) Subdivision in 2 subgroups, according to the ability of the patients to decrease urinary pH below 5.3 (upper panel) or not (lower panel). B) Subdivision into four subgroups according the ability of the subjects to decrease urinary pH below 5.3 and to reach maximal urinary ammonium excretion (U.NH4+) to 33 μEq/min. Green: idiopathic hypocitraturia defined to both appropriate adaptation of both pH and U.NH4+). Blue: appropriate maximal urinary ammonium excretion in spite of insufficient urinary acidification (high U. pH, high U.NH4+ group); Purpura: Inappropriate urinary acidification but appropriate U.NH4+ (high U. pH, low U.NH4+ group); Red: Appropriate urinary acidification and U.NH4+ (low U. pH, low U.NH4+ group). Points represent the median value, whiskers represent the interquartile range.
Table 3.
Demographic and biological characteristics of the 56 patients with normal baseline plasma HCO3- undergoing the acute acid load test.
Table 4.
Biological results after the acute acid load test of the 56 patients with normal baseline plasma HCO3-.
Fig 2.
Urinary ammonium excretion rates after acute acid load in patients with a normal acid-base status, according to the urinary acidification defect.
All urinary pH values measured within the 6 hours after the acid load are plotted against all the corresponding NH4+ excretion rates (logarithmic value). Patients were classified in four subgroups according to the minimal pH value and to the maximal NH4+ excretion rate obtained within this 6 hours: idiopathic hypocitraturia (green): min. urine pH < 5.3, max. NH4+ ≥ 33 μEq/min.; high U. pH, high U. NH4 (blue): min. urine pH ≥ 5.3, max. NH4+ ≥ 33 μEq/min.; high U. pH, low U. NH4 (purpura): min. urine pH ≥5.3, max. NH4+ < 33 μEq/min.; low U. pH, low U. NH4 (red): min. urine pH < 5.3, max. NH4+ < 33 μEq/min. The thick line represents the regression line and the thin lines the 95% confidence intervals of the idiopathic hypocitraturia group (reference group). The horizontal dotted line is the NH4+ excretion rate cut-off set at 33 μEq/min. The vertical dotted line is the urinary pH cut-off set at 5.3.
Fig 3.
Subgroups classifications: idiopathic hypocitraturia: min. urine pH < 5.3, max. NH4+ ≥ 33 μEq/min.; high U. pH, high U. NH4: min. urine pH ≥ 5.3, max. NH4+ ≥ 33 μmol/min.; high U. pH, low U. NH4: min. urine pH ≥5.3, max. NH4+ < 33 μEq/min.; low U. pH, low U. NH4: min. urine pH < 5.3, max. NH4+ < 33 μEq/min. AE1: chloride bicarbonate exchanger; AI: autoimmune disease; E161K: missense polymorphism (p.Glu161Lys) of the ATP6V1B1 gene; H+-ATPase: B1 and a4-subunits of the apical H+-ATPase, including missense polymorphism (p.Glu161Lys) of the ATP6V1B1 gene; HCO3-: plasma bicarbonate; NH4Cl: ammonium chloride. AI diseases are allocated as follows: "idiopathic hypocitraturia": spondyloarthritis (N = 1), rheumatic polyarthritis (N = 1); "high U.pH, high U.NH4": Gougerot-Sjögren disease (N = 1), spondylarthritis (N = 1), primary biliary cirrhosis (N = 1); "high U.pH, low U.NH4+": Crohn’s disease (N = 1).