Table 3.

2 × 2 tables stratified by serum total CO₂, approximated HCO₃⁻ concentration and measured HCO₃⁻ concentration for low bicarbonate (HCO₃⁻ < 24 mmol/L) and high bicarbonate (HCO₃⁻ ≥ 24 mmol/L)

	HCO3−		Total
	Low bicarbonate (HCO3− < 24 mmol/L)	High bicarbonate (HCO3− ≥ 24 mmol/L)
Serum total CO2
Low serum total CO2 (serum total CO2 < 24 mmol/L)	121	46	167
High serum total CO2 (serum total CO2 ≥ 24 mmol/L)	11	127	138
Total	132	173	305
Approximated HCO3−
Low approximated HCO3−(approximated HCO3− < 24 mmol/L)	112	21	133
High approximated HCO3− (approximated HCO3− ≥ 24 mmol/L)	20	152	172
Total	132	173	305

CO₂, carbon dioxide; HCO₃⁻, bicarbonate ion.