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    PJIs Can Be Missed in Patients with Rheumatic Diseases, Study Finds

    Standard diagnostic methods are not adequate to identify periprosthetic joint infections (PJI) in patients with rheumatic diseases, according to findings from a new study presented by researchers from Hospital for Special Surgery (HSS) at the 2019 ACR/ARP Annual Meeting.

    Lead study author Susan M. Goodman, MD, a rheumatologist at HSS, said that although patients with rheumatic diseases are more prone to developing PJIs than total joint arthroplasty patients without a rheumatic disease, it is also harder to make a PJI diagnosis in this population.

    “If a patient with osteoarthritis comes in with a swollen and inflamed prosthetic joint, it is an infection until proven otherwise,” she said. “But for patients with rheumatoid arthritis, it can be very hard to sort out whether this is part of an overall flare of disease or if it is a true infection. None of the available tests are that helpful.”

    The researchers launched the new study to examine the clinical and microbiological features of PJIs in total hip arthroplasty (THA) and total knee arthroplasty (TKA) patients with rheumatic diseases and osteoarthritis. Using the HSS institutional PJI registry, the researchers created a retrospective cohort of 807 patients who underwent THA and TKA between 2009 and 2016 and subsequently developed a PJI. In this cohort, 36 patients had a rheumatic disease and 771 did not. Culture-negative cases were defined as PJIs with no evidence of microbial growth in intraoperative cultures; culture-positive PJIs were defined by positive microbial growth.

    Among the findings, the researchers discovered that patients with rheumatic diseases had a higher proportion of culture-negative PJIs than patients without a rheumatic disease, 27% versus 14%, respectively (P=0.02).

    “Patients with rheumatic diseases who were culture negative were less likely to meet the pathology criteria for infections than the [patients] who were culture positive, and they did a little worse,” Dr. Goodman said. One-year survivorship of culture-negative osteoarthritis and culture-negative rheumatic disease were 87% and 66%, respectively, and 47% for culture-positive rheumatic disease.

    “The main message is that patients with rheumatic disease seem to have more culture-negative prosthetic joint infections than patients with osteoarthritis, but what we don’t know is what that means in terms of long-term management,” Dr. Goodman said.

    “We had the feeling that we were missing something with our rheumatic disease patients who were coming in with prosthetic joint infections, so I wasn’t surprised by our findings, but it pointed out how much more we need to do to really understand this.”  

    Dr. Goodman said the next step is to do a prospective study in patients with rheumatic disease, which will provide the standard diagnostic tests for PJIs but will also use next-generation sequencing, including cell-free DNA, methods to better identify bacteria present in tissue.

    Source

    Mirza SZ, Richardson S, Kahlenberg C, Blevins J, Demetres M, Martin L, Szymonifka J, Sculco PK, Figgie MP, Goodman SM. Diagnosing Prosthetic Joint Infections in Patients with Inflammatory Arthritis (Abstract 1229). Presented at the 2019 ACR/ARP Annual Meeting, November 8-13, Atlanta, Georgia.