Point-of-Care Measurement of Serum Creatinine in the Intensive Care Unit

Figures & data

Table 1. Analytes of interest and arterial gases values for variables analyzed for interaction with creatinine.

	Mean (± standard deviation)	Median (interquartile range)
Bilirubin (μmol/L)	33.3 (±60.9)	16.5 (16)	3–532	0–15
Albumin (g/L)	26 (±5.7)	26 (7)	14–41	36–48
Hemoglobin (g/dL)	10 (±2.3)	9.5 (3.4)	6.4–16.9	11.5–16.5
pH	7.41 (±0.07)	7.42 (0.09)	7.08–7.59	7.35–7.45
pCO2 (mmHg)	41 (±8.2)	40 (10)	19.2–79.2	35–48
pO2 (mmHg)	128 (±89)	102 (53)	26–561	83–108
sO2 (%)	95.4 (±8.4)	97.7 (2.9)	45.8–100	95–98
Carboxyhemoglobin (%)	0.8 (±0.5)	0.8 (0.6)	0–2.9	0.5–1.5
Methemoglobin (%)	0.6 (±0.3)	0.6 (0.3)	0–1.4	0–1.5
Potassium (mmol/L)	4.1 (±0.6)	4 (0.5)	1.9–7.1	3.5–5.0
Sodium (mmol/L)	140 (±6.4)	139 (7)	126–168	136–146
Ionized calcium (mmol/L)	1.08 (±0.08)	1.1 (0.1)	0.8–1.32	1.15–1.29
Chloride (mmol/L)	103 (6)	103 (7)	90–131	95–110
Glucose (mmol/L)	8 (±2.5)	7.5 (2.7)	2.7–22.5	3.9–5.8
Lactate (mmol/L)	1.7 (±1.7)	1.2 (0.8)	0.4–11.8	0.5–1.6
Urea (mmol/L)	11.5 (±9.2)	9.1 (8.8)	1.2–56.8	3.0–10.0
Magnesium (mmol/L)	1.05 (±0.24)	1.04 (0.3)	0.6–2.55	0.6–1.1
Phosphate (mmol/L)	1.3 (±0.5)	1.2 (0.6)	0.2–3.7	0.8–1.4

Figure 1. Correlation plot of central laboratory (CrL) versus point-of-care POCT (CrP) creatinine values.

Figure 2. Bland–Altman analysis of creatinine measurement with laboratory (CrL) and point-of-care (POCT; CrP) techniques.

Table 2. Multivariate regression analysis of factors affecting δCr (difference in creatinine calculated as CrL – CrP).

				95% confidence intervals
Bilirubin (μmol/L)	−0.034	0.012	0.006	−0.059;−0.010
Albumin (g/L)	−0.445	0.129	0.001	−0.699;–0.192
Hemoglobin, Hb (g/dL)	1.339	0.342	<0.001	0.664;2.014
Ionized calcium (mmol/L)	−30.356	8.533	<0.001	−47.185;–13.528
Lactate (mmol/L)	1.350	0.459	0.004	0.445;2.255

Notes: δCr used as the dependent variable. Serum chloride, oxyhemoglobin (%), and oxygen saturation (%) excluded from the model due to multicollinearity.