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Home , Gout, Septic arthritis

Prognosis Risk for septic was increased in Lim SY, Lu N, Choi HK. in patients: a population-based cohort study. (Oxford). adults with incident diagnosis of gout 2015;54:2095-9.

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Question Commentary In adults with an incident diagnosis of gout, what is the risk for We know that patients with have an increased septic arthritis? risk for acute septic arthritis, and case reports have confirmed that septic arthritis can also be associated with acute gouty arthritis. Lim Methods and colleagues, in a novel cohort analysis of a large UK database, Design: Inception cohort followed for a mean of 5 years. show that a first bout of gout was associated with a 2.6-fold in- creased risk for septic arthritis compared with patients without Setting: The Health Improvement Network (THIN) database, gout. However, due to numerous clinical exclusions (including pre- representing 580 general practices in the UK. existing gout), they may have underestimated the true increased risk for septic arthritis in patients with gout. Patients: 72 073 adults ≥ 40 years of age (mean age 65 y, 71% men) who had an incident diagnosis of gout. The control group Acute inflammatory monoarticular and oligoarticular arthritis are comprised 358 342 adults without gout, matched for age, sex, common conditions with an extensive , date of study entry, and enrollment year. Exclusion criteria were most commonly acute crystal arthritis (gout or, less frequently, history of septic arthritis, gout, , rheumatoid arthri- calcium pyrophosphate deposition disease or pseudogout), tis, or other inflammatory rheumatic condition (seronegative rheumatoid arthritis, or septic arthritis. Diagnostic workup man- , , connective tissue dates synovial fluid aspiration to examine for the presence of disease, vasculitides, or crystal ). crystals and to obtain a , nucleated cell count and differential, and bacterial culture (1). Prognostic factors: Lifestyle factors (smoking and use), Although a high leukocyte count in the synovial fluid (> 50 000/ , socioeconomic deprivation index (Townsend 3 Deprivation Index score), number of physician visits, glucocorti- mm with > 90% neutrophils) is highly suggestive of septic ar- thritis (2, 3), acute gout and pseudogout are also characterized costeroid use, and Charlson index. by high leukocyte counts, typically 25 000 to 50 000/mm3 with Outcomes: Incident septic arthritis diagnosis associated with neutrophilic predominance (3). Crystals can be identified in the hospital admission or prescription for an . synovial fluid of most patients with acute crystal arthritis (4), while about 75% of patients with septic arthritis will have a posi- Main results tive culture, with up to 50% having a positive Gram stain (2, 3). 90 cases of septic arthritis occurred in the gout group and 166 What is challenging is the 5% of patients with acute monoarticu- cases in the control group. At 5-year follow-up, patients with lar arthritis or with crystals who also have septic incident gout had increased risk for septic arthritis compared arthritis (5). with those without gout (Table). The study by Lim and colleagues reaffirms that synovial fluid obtained from patients with acute monoarticular or oligoarticu- Conclusion lar arthritis must routinely be analyzed for even when Adults with an incident diagnosis of gout had increased risk for urate crystals are seen. Because the results of synovial fluid cul- septic arthritis. ture will be negative in up to 25% of patients with septic arthritis Source of funding: No external funding. (2, 5)—especially if the patient has received empirical antimicro- bial therapy—we should retain an aliquot of synovial fluid from For correspondence: Dr. S.Y. Lim, Harvard Medical School, patients with acute crystal arthritis with negative cultures for Boston, MA, USA. E-mail [email protected].  later analysis by 16S ribosomal RNA polymerase chain reaction. This assay can rapidly and accurately identify the bacterial in culture-negative septic arthritis in up to 50% of cases (6). If the patient has a high or signs of systemic in- Risk for septic arthritis in adults with incident gout* fection at the outset or does not respond promptly to targeted antiinflammatory therapy, but Gram stain and bacterial cultures Outcome Incidence/1000 Hazard ratio (CI) at a are negative, the specimen can be tested for evidence of infec- person-y (95% CI) mean follow-up of 5 y† tion by 16S ribosomal RNA polymerase chain reaction. Gout Control Dennis G. Maki, MD, MACP Septic arthritis 0.24 (0.20 to 0.30) 0.09 (0.08 to 0.10) 2.60 (1.93 to 3.51) University of Wisconsin School of Medicine and Public Health *Abbreviations defined in Glossary. Madison, Wisconsin, USA †Adjusted for smoking, alcohol use, body mass index, socioeconomic deprivation index (Townsend Deprivation Index score), number of physician visits, glucocortico- References steroid use, and Charlson comorbidity index. 1. Ma L, Cranney A, Holroyd-Leduc JM. Acute : what is the cause of my patient's painful swollen ? CMAJ. 2009;180:59-65. 2. Margaretten ME, Kohlwes J, Moore D, Bent S. Does this adult patient have septic arthritis? JAMA. 2007;297:1478-88. 3. Lenski M, Scherer MA. Analysis of synovial inflammatory markers to differ infectious from gouty arthritis. Clin Biochem. 2014;47:49-55. 4. Gordon C, Swan A, Dieppe P. Detection of crystals in synovial fluids by light microscopy: sensitivity and reliability. Ann Rheum Dis. 1989;48:737-42. 5. Papanicolas LE, Hakendorf P, Gordon DL. Concomitant septic arthritis in crystal monoarthritis. J Rheumatol. 2012;39:157-60. 6. Kim H, Kim J, Ihm C. The usefulness of multiplex PCR for the identification of in joint infection. J Clin Lab Anal. 2010;24:175-81.

஽ 2015 American College of Physicians JC12 ACP Journal Club Annals of Internal Medicine 15 Dec 2015 Downloaded From: http://annals.org/ by a Ebling Library Information Research User on 01/28/2016