Performance Evaluation of the ABX Micros CRP

Performance Evaluation of the ABX Micros CRP: The First Instrument Reporting a Complete Blood Count, 3-Part Leukocyte Differential, and C-Reactive Protein Quantitation

Bruce H. Davis, Nancy C. Bigelow

Laboratory Hematology 7:69-74
©2001 Carden Jennings Publishing Co., Ltd.

ABX Diagnostics has developed the ABX Micros CRP analyzer, the first instrument to provide both a complete blood count (CBC) with a 3-part differential and a quantitative C-reactive protein (CRP) determination. The CRP measurement is based on a whole-blood immunoturbidimetric method using latex beads coated with anti-CRP-specific-monoclonal antibody. The evaluation reported here of the linearity, sensitivity, precision, carryover, and clinical performance of the ABX Micros CRP was performed prior to release of the instrument in the United States. Precision of CRP analysis was assessed by replicate determinations of K₃EDTA-anticoagulated whole-blood samples with CRP values in the range of <0.4 mg/dL to 10 mg/dL. Linearity was evaluated by assaying pooled normal samples spiked with CRP control material. The stability of CRP was studied in blood samples held at both room temperature and refrigerated conditions over a 72-hour period. Correlation studies were performed by analyzing 100 blood samples on the ABX Micros CRP and comparing the results with those obtained using the Roche COBAS Integra CRP assay, which is based on latex nephelometry. Within-run and between-run precision of both CBC and CRP values had a coefficient of variation (CV) of <10%. Excellent linearity was observed and there was no significant carryover. Correlation of CRP with the Roche COBAS Integra was excellent with a slope of approximately 0.98, no significant bias, and an r2 value of >0.99. No interference was seen in the analysis of any of the samples from patients with clinical conditions associated with interfering substances. Samples held at either 25°C or 4°C were stable for 48 hours. The CRP sensitivity was greater than the manufacturer's claim of 0.2 mg/dL. The ABX Micros CRP demonstrated performance suitable for clinical practice. The ease of use, small sample volume (18uL), and rapid turnaround time (<5 minutes for CBC and CRP) are features that will make this instrument useful in point-of-care testing areas including both adult and pediatric intensive care units and in office laboratories, particularly those of pediatricians, rheumatologists, and infectious disease specialists.

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