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Abstract
Background
Early detection of underlying renal dysfunction among emergency patients is important, particularly before imaging studies using contrast media. The estimated glomerular filtration rate (eGFR) calculated from creatinine values is useful in situations requiring rapid evaluation and detection of renal impairment.
Methods
We evaluated the concordance of eGFR determined using the whole blood creatinine test by Nova CCX (Cr-CCX WB; Nova Biomedical, USA) method and the serum creatinine test by Roche Integra 800 (Cr-RE Serum; Roche Diagnostics, Switzerland) enzymatic method, which is known to be traceable to the isotope dilution mass spectrometric (ID-MS) reference method.
Results
Compared to Cr-RE Serum (x), Cr-CCX WB (y) showed good correlation but unacceptable total error and negative proportional bias (Deming regression, y=0.92x+0.02; r=0.98; n=61). However, when we adjusted the Cr-CCX WB values with a new slope and offset derived from the Deming regression analysis with Cr-RE Serum, the concordance rate improved from 0.77 to 0.93 (as measured by kappa statistics), and total errors became acceptable except at 1 level. When we used the ID-MS traceable eGFR formula, the Nova CCX demonstrated sufficient sensitivity (93.5%) and specificity (100%) for the detection of renal dysfunction (eGFR less than 60 mL/min/1.73 m2) in patients.
Conclusions
We concluded that if we adjusted the harmonizing factors of Nova CCX according to the ID-MS traceable method, then the Nova CCX might be a relatively accurate point-of-care creatinine analyzer for detecting renal dysfunction among patients undergoing urgent imaging studies with radiological contrast media.
Figures and Tables
Fig. 1
Deming fit of 61 creatinine values determined using Nova CCX and Roche enzymatic method after adjustment of harmonizing factors.
Fig. 2
Deming fit of eGFR values lower than 90 mL/min/1.73 m2 (n=43) determined Nova CCX and Roche enzymatic method after adjustment of harmonizing factors; correlation coefficient, r=0.98.
Table 1
Evaluation of bias and total error of Nova CCX creatinine determination
*Remark, 'unacceptable', 'acceptable', and 'desirable' were based on TE (%) described in the reference #9, i.e., desirable TE, ≤7.6%; acceptable TE, 7.6-11.4%; unacceptable, TE>11.4%.
Abbreviations: CFS, commutable frozen serum; ReCCS, Reference material institute for clinical chemistry standards; CVa, analytical coefficient of variation, total precision of creatinine levels; TE, total error=bias+1.96×Cva.
References
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