Table 1.

Changes in pH, pCO2, and HCO3 concentrations after CO2 loss because of shaking in oil-free acidic urine samples (n=97) and two subgroups (group I: pH≤6.0; group II: pH>6.0)

All (n=97; pH=5.0–7.0)Group I (n=63; pH≤6.0)Group II (n=34; pH>6.0)P Value
Baseline pH5.84 (5.44–6.25)5.56 (5.33–5.83)6.39 (6.22–6.59)<0.001
 pH after shaking5.93 (5.50–6.54)5.65 (5.40–5.93)a6.79 (6.52–7.04)a<0.001
 ΔpH0.12 (0.07–0.29)0.08 (0.05–0.12)0.36 (0.23–0.51)<0.001
Baseline pCO2 (mmHg)47.3 (37.2–62.7)41.8 (36.0–50.1)59.7 (47.5–70.8)<0.001
 pCO2 after shaking12.0 (10.3–15.0)a12.1 (10.2–15.4)a11.7 (10.2–14.4)a0.73
 ΔpCO235.4 (24.8–50.0)30.1 (21.6–38.6)48.3 (37.1–56.9)<0.001
 reduction rate (%)76.4 (66.5–80.5)70.3 (62.1–78.0)79.3 (77.3–80.9)<0.001
Baseline [HCO3] (mmol/L)0.75 (0.26–2.41)0.33 (0.21–0.75)3.59 (1.94–5.37)<0.001
 [HCO3] after shaking0.23 (0.10–0.91)a0.12 (0.07–0.23)a1.90 (0.81–3.53)a<0.001
 Δ[HCO3]0.48 (0.15–1.15)0.19 (0.12–0.49)1.43 (0.86–2.53)<0.001
 reduction rate (%)60.4 (51.4–71.0)64.2 (55.9–73.5)52.1 (33.4–64.6)<0.001
  • All data are expressed as median values with interquartile range. P value is group I versus group II.

  • a P<0.001 versus the corresponding baseline value.