The Journal of Arthroplasty
Volume 23, Issue 2 , Pages 182-187, February 2008

Determining “True” Leukocytosis in Bloody Joint Aspiration

Investigations were performed at the Rothman Institute of Orthopedics, Thomas Jefferson University, Philadelphia, Pennsylvania.

Received 2 May 2007; accepted 22 August 2007.

Abstract 

This study intends to determine the diagnostic value of implementing a corrective formula that can adjust for serum leukocytes in bloody joint fluid. Our cohort included 91 infected and 37 aseptic total knee arthroplasties. Joint fluid leukocyte count (>1760/μL) and neutrophil percentage (>73%) were the cutoff values for deep infection. The adjusted fluid leukocyte counts were calculated using the following simple formula: WBCadjusted = WBCobserved − [(WBCblood × RBCfluid/RBCblood)]predicted. Adjusted fluid cell counts of only 5 infected patients dropped below the cutoff value, whereas the remaining 86 maintained a high cell count. Ten noninfected patients had false-positive cell counts, 6 of which were successfully corrected to levels below the designated thresholds. The aspirates that were corrected had a greater number of introduced white blood cells. This study suggests that our corrective formula can detect false-positive joint aspirations without jeopardizing the diagnosis of periprosthetic infection.

Key words: total knee arthroplasty, traumatic aspiration, periprosthetic infection, correction

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 Javad Parvizi, MD, FRCS, received funding from Stryker Orthopaedics, Mahwah, New Jersey, for his research.

PII: S0883-5403(07)00512-8

doi:10.1016/j.arth.2007.08.016

The Journal of Arthroplasty
Volume 23, Issue 2 , Pages 182-187, February 2008