Agreement between Arterial and Capillary pH, pCO₂, and Lactate in Patients in the Emergency Department

Table 2

Cutoff levels, sensitivity, and specificity for capillary BGA in detecting altered pH, pCO₂, or lactate.

Patients, no. (%)
Value	Cutoff level	Sensitivity (%); (95% CI)	Specificity (%); (95% CI)	True positive	False negative	False positive	True negative	PPV (%); (95% CI)	NPV (%); (95% CI)
Arterial pH (acidosis)	7.361	100 (92.4–100)	93.3 (88.1–96.8)	47 (23.9)	0 (0)	10 (5.1)	140 (71.1)	82.5 (72.1–89.5)	100
	7.34	97.9 (88.7–100)	97.3 (93.3–99.3)	46 (23.7)	1 (0.5)	4 (2.0)	146 (74.5)	92 (81.4–96.8)	99.3 (95.5–99.9)
	7.288	53.1 (38.1–67.9)	100 (97.6–100)	25 (12.7)	22 (11.2)	0 (0)	150 (76.6)	100	87.2 (83.4–90.2)
Arterial pH (alkalosis)	7.4	100 (91.4–100)	62.2 (54.1–69.8)	41 (20.8)	0 (0)	59 (30)	97 (49.2)	41.0 (36.2–45.9)	100
	7.447	65.9 (49.4–79.9)	95.5 (91.0–98.2)	27 (13.1)	14 (7.1)	7 (3.5)	149 (75.6)	79.4 (64.4–89.2)	91.4 (87.4–94.2)
	7.471	39.0 (24.2–55.5)	100 (97.7–100)	16 (8.1)	25 (12.7)	0 (0)	156 (79.2)	100	86.2 (83.0–88.9)
pCO2 (mmHg) (hypercapnia)	35.8	100 (94.6–100)	42.0 (33.4–50.9)	66 (33.5)	0 (0)	76 (38.6)	55 (27.9)	46.5 (42.9–50.1)	100
	45.9	89.4 (79.4–95.6)	96.2 (91.3–98.8)	59 (29.9)	7 (3.6)	5 (2.5)	126 (63)	92.2 (83.3–96.6)	94.7 (89.9–97.3)
	56.5	51.5 (38.9–64.0)	100 (97.2–100)	34 (17.3)	32 (16.2)	0 (0)	131 (66.5)	100	80.4 (76.2–84.0)
Lactate (mmol/L) (hyperlactatemia)	1.3	100 (92.5–100)	23.0 (16.2–31.0)	47 (25.8)	0 (0)	104 (57.1)	31 (17.3)	31.1 (29.2–33.1)	100
	3.5	66.0 (50.7–79.1)	92.6 (86.8–96.4)	31 (17.3)	16 (8.8)	10 (5.5)	125 (68.7)	75.6 (62.3–85.4)	88.7 (84.0–92.1)
	4.4	46.8 (32.1–61.9)	100 (97.3–100)	22 (12.1)	25 (13.7)	0 (0)	135 (74.2)	100	84.4 (80.5–87.6)

PPV, positive predictive value; NPV, negative predictive value.