Could Inflammatory Arthritis Falsely Indicate Joint Infection?

A research team from New York’s Hospital for Special Surgery (HSS) pondered that particular question, noting that the elevated inflammatory markers seen in active inflammatory arthritis may well mimic the inflammatory markers seen in peri-prosthetic joint infection (PJI). So, they designed the following study to test that hypothesis.

Their resulting work, “Clinical and Histological Features of Prosthetic Joint Infections May Differ in Patients With Inflammatory Arthritis and Osteoarthritis,” appears in the May 2023 edition of HSS Journal: The Musculoskeletal Journal of Hospital for Special Surgery.

“There are overlapping clinical and lab features of flares of inflammatory arthritis and prosthetic joint infection including fever and joint swelling and elevated synovial white blood cell counts that make rapid diagnosis and differentiation challenging,” explained co-author Susan M. Goodman, M.D., a rheumatologist at HSS, to OTW. “We have been studying this to find ways to make a diagnosis more efficiently, as delays in appropriate therapy, including surgical debridement of infections, decrease the success rate.”

The researchers conducted a retrospective analysis of HSS patients who had been treated with total hip arthroplasty (THA) or total knee arthroplasty (TKA) and were also treated for PJI from 2009 to 2018.

The research team collected data from hematoxylin and eosin slides of osteoarthritis (OA) and inflammatory arthritis PJI cases—matching them 3:1, respectively, by age, sex, and culture status. From that data, the team was able to identify 807 PJI cases (36 inflammatory arthritis and 771 osteoarthritis cases).

According to the authors, “Patients with inflammatory arthritis presented younger, had a higher Charlson Comorbidity Index, more frequently used glucocorticoids, were more likely women, and had a higher proportion of culture-negative PJI compared with osteoarthritis patients.”

“Of the 88 inflammatory arthritis cases reviewed for histopathology, a higher proportion of culture-positive than culture-negative PJI cases had >10 polymorphonuclear leucocytes per high-power field and met Musculoskeletal Infection Society criteria but presented with less chronic inflammation.”

“We found more culture negative cases among the patients with inflammatory arthritis, but we could not determine with certainty if this related to prior antibiotic use or infection chronicity, or if these cases were misdiagnosed flares. More investigation is warranted.”

When OTW asked if they were at all surprised by the results, Dr. Goodman stated, “No—we have been suspicious that there was overlap in the diagnosis of PJI and flares of inflammatory arthritis, and we have been very interested in improving our ability to discriminate between the two entities. This would enable us to avoid unnecessary surgery when the patient is actually flaring, as well as to make a rapid and accurate diagnosis in infected patients. We need to develop better diagnostic tests to use in this setting.”