Comparison between point‐of‐care testing from capillary samples and conventional laboratory testing from venous samples for white blood cells and C‐reactive protein in a pediatric outpatient setting

Abstract

Abstract Background Studies on the accuracy of point‐of‐care (POC) testing using capillary samples are scarce. Therefore, this study aimed to assess the analytical accuracy of POC testing for white blood cell (WBC) and C‐reactive protein (CRP) using capillary samples compared with conventional central laboratory testing using venous samples in a pediatric ambulatory care setting. Methods This was a retrospective study including patients younger than 18 years who underwent concurrent WBC and CRP evaluations via capillary and subsequent venous sampling within a 2‐h window. Capillary and venous blood samples were collected using finger prick and standard venipuncture techniques, respectively. Capillary blood analysis was performed using a Microsemi CRP device. Venous samples were measured in the hospital's central laboratory. The agreement between the capillary POC and venous laboratory results was evaluated using Bland‐Altman analysis. Results A total of 277 pediatric patients were included in this study. The median age of the participants was 1 year (interquartile range: 0–2 years). The mean difference between the capillary and venous measurements for WBC was −18 × 100/μL with 95% limits of agreement of −73 × 100/μL to 37 × 100/μL. The mean difference between the capillary and venous measurements for CRP was −0.25 mg/dL with 95% limits of agreement of −2.1 mg/dL to 1.6 mg/dL. Conclusions POC CRP testing via capillary sampling by finger prick demonstrated sufficient accuracy. POC CRP testing has the potential to be a valuable instrument for clinical decision making, particularly in screening febrile outpatient children.

Keywords

• capillary blood
• child
• C‐reactive protein
• point‐of‐care
• white blood cell