The C-Reactive Protein May Not Detect Infections Caused by Less-Virulent Organisms

• Published in: The Journal of arthroplasty Vol. 31; no. 9; pp. 152 - 155
• Main Authors: Deirmengian, Carl A., MD, Citrano, Patrick, Gulati, Simmi, Kazarian, Erick, BA, Stave, James, PhD, Kardos, Keith, PhD
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.09.2016
• Subjects: Arthritis, Infectious - diagnosis; Arthritis, Infectious - microbiology; bacterial infection; C-reactive protein; C-Reactive Protein - analysis; diagnostic testing; Host-Pathogen Interactions; Humans; Orthopedics; periprosthetic joint infection; Prosthesis-Related Infections - diagnosis; Prosthesis-Related Infections - microbiology; Retrospective Studies; revision arthroplasty; Staphylococcus aureus - physiology; Staphylococcus epidermidis - physiology; Synovial Fluid - chemistry; Synovial Fluid - microbiology; periprosthetic joint infection; revision arthroplasty; C-reactive protein; diagnostic testing; bacterial infection
• ISSN: 0883-5403; 1532-8406
• DOI: 10.1016/j.arth.2016.01.060

Abstract Introduction The aim of the present study was to evaluate the influence of organism type on the performance of the synovial fluid CRP test. Methods We retrospectively reviewed the results of 21,422 synovial fluid samples sent to one common laboratory for the purpose of diagnostic testing for periprosthetic joint infection (PJI). Both a synovial fluid CRP result and a positive culture were present for 1,789 submitted samples. The cultured organisms were grouped by species, virulence, and gram-type, and the median CRP level was determined for each group. Results The median synovial fluid CRP level was significantly lower for less-virulent organisms, when compared to those organisms classified as virulent (15.10 mg/L vs. 32.70 mg/L; p<0.0001). Some less-virulent species such as yeast and S. epidermidis were associated with a four to ten times lower CRP response than those of virulent organisms such as S. agalactiae and S. aureus (p<0.0001). Bacterial Gram-type had no influence on the median CRP result. The rate of false-negative CRP values was 50.9% for yeast, 29.4% for S. epidermidis , 28.5% for all less-virulent organisms, and 11.6% for all virulent organisms. Conclusion The CRP response appears to be highly dependent on the infecting organism, and is more likely to provide false-negative results in the setting of less-virulent organisms. Although the use of a CRP level is an important part of the work-up for PJI, surgeons must be aware that this protein may yield a false-negative result in the setting of less-virulent organisms.