Evaluation of a handheld creatinine measurement device for real-time determination of serum creatinine in radiology departments

Table 1 Means, standard deviations, calculated difference between the measured serum creatinine level (mg/dL) using StatSensor™ creatinine and the laboratory reference, Pearson's correlation coefficients, paired t-test and Maloney-Rastogi test, subdivided by study centre, pre- and post-offset correction

			Centre 1	Centre 2	Mean (centre 1 +2)	Pearson correlation coefficient	P value (paired t-test)	P value (Maloney-Rastogi-test)
StatSensor™
cSCr	Pre offset	Device A	0.80 ± 0.34	0.89 ± 0.27	0.85 ± 0.31	Inter-device evaluation (Device A vs B)
		Device B	0.81 ± 0.34	0.89 ± 0.26	0.85 ± 0.30	Center 1 = 0.97	Center 1 = 0.404	Center 1 = 0.480
		Difference between Device A vs B	-0.01 ± 0.09	0.00 ± 0.09		Center 2 = 0.95	Center 2 = 0.689	Center 2 = 0.521
		Mean (Device A + B)	0.80 ± 0.34	0.89 ± 0.26	0.85 ± 0.31
	Post offset	Device A	0.97 ± 0.50
		Device B	0.96 ± 0.50
Laboratory reference
vSCr			0.96 ± 0.42	1.02 ± 0.26	0.99 ± 0.35	Inter-method evaluation (cSCr vs vSCr)
Difference
cSCr - vSCr	Pre offset	Mean (Device A + B)	-0.16 ± 0.16a	-0.14 ± 0.15b	-0.15 ± 0.15c		< 0.0001a,b,c	< 0.0001a,c; 0.9962b
		Device A	-0.16 ± 0.16			0.93	< 0.0001	< 0.0001
		Device B	-0.15 ± 0.17			0.92	< 0.0001	< 0.0001
	Post offset	Device A	0.01 ± 0.19			0.93	0.638	< 0.0001
		Device B	0.00 ± 0.20			0.92	0.955	< 0.0001

cSCr: Capillary serum creatinine; vSCr: Venous serum creatinine.

Table 2 Pearson's correlation coefficients for creatinine values measured using the laboratory reference (venous serum creatinine) and StatSensor™ creatinine, subdivided by study centre, renal function and gender

vSCr (laboratory) vs	cSCr (StatSensor™)		Overall
	Device A	Device B
Study centre
Centre 1	0.93	0.92	0.93
Centre 2	0.85	0.82	0.84
Overall	0.90	0.88	0.89
Renal function
vSCr < 1.2 mg/dL	0.66	0.59	0.63
vSCr > 1.2 mg/dL	0.91	0.90	0.91
Gender
Male	0.91	0.89	0.90
Female	0.81	0.78	0.80

cSCr: Capillary serum creatinine; vSCr: Venous serum creatinine.

Table 3 Results of the re-analysed data from centre 1 (n = 201), shown pre- and post-implementation of the curve offset, separated for the two devicespre- and post-offset correction

	Device	Slope	Intercept (mg/dL)	r2	Mean difference (mg/dL) (method-difference)	STDV of differences (method-difference)	% bias
Pre offset	A	0.765	0.065	0.870	-0.16	0.16	-15.54
	B	0.745	0.089	0.845	-0.16	0.17	-14.76
Post offset	A	1.110	-0.099	0.870	0.01	0.19	0.39
	B	1.088	-0.084	0.845	0.00	0.20	-0.02

The results are given as slope, intercept, mean difference, standard deviation and percentage bias.

Table 4 Sensitivity, specificity, positive predictive value, negative predictive value and mean values for the cut-off value of 1.2 mg/dL, of the re-analysed data from centre 1 (n = 201), shown pre- and post-implementation of the curve offset, separated for the two devices (%)

	Device	Sensitivity	Specificity	PPV	NPV
Pre offset	A	35.48	99.41	91.67	89.42
	B	41.94	99.41	92.86	90.37
Post offset	A	80.65	98.26	89.29	95.57
	B	70.97	94.12	68.75	94.67
	Mean (A + B)	77.42	94.71	72.37	95.83

PPV: Positive predictive values; NPV: Negative predictive values.