The analysis of false prolongation of the activated partial thromboplastin time (activator: silica): Interference of C‐reactive protein

Background To investigate the effect of C‐reactive protein on the activated partial thromboplastin time ( APTT ) (different activators) in different detecting systems. Methods The C‐reactive protein and coagulation test of 112 patients with the infectious disease were determined by automation protein analyzer IMMAG 800 and automation coagulation analyzer STA ‐R Evolution, respectively. The pooled plasma APTT with different concentrations of C‐reactive protein was measured by different detecting system: STA ‐R Evolution (activator: silica, kaolin), Sysmex CS ‐2000i (activator: ellagic acid), and ACL TOP 700 (activator: colloidal silica). In addition, the self‐made platelet lysate (phospholipid) was added to correct the APTT prolonged by C‐reactive protein (150 mg/L) on STA ‐R Evolution (activator: silica) system. Results The good correlation between C‐reactive protein and APTT was found on the STA ‐R Evolution (activator: silica) system. The APTT on the STA ‐R Evolution (activator: silica) system was prolonged by 24.6 second, along with increasing C‐reactive protein concentration. And the APTT of plasma containing 150 mg/L C‐reactive protein was shortened by 3.4‐6.9 second when the plasma was mixed with self‐made platelet lysate. However, the APTT was prolonged unobviously on other detecting systems including STA ‐R Evolution (activator: kaolin), Sysmex CS ‐2000i, and ACL TOP 700. Conclusion C‐reactive protein interferes with the detection of APTT , especially in STA ‐R Evolution (activator: silica) system. The increasing in C‐reactive protein results in a false prolongation of the APTT (activator: silica), and it is most likely that C‐reactive protein interferes the coagulable factor binding of phospholipid.