Rapid access microscopy and real-time case discussion via a secure messaging app improves diagnostic accuracy and management of acute hot swollen joints

Abstract

Patients with acute swollen joints are often presumed to have septic arthritis, leading to intravenous antibiotics and arthroscopic washout. Previously at our centre, joint fluid aspirates often lacked crystal analysis, resulting in excess culture-negative septic arthritis diagnoses. We developed a 'Hot Joint Pathway', hypothesising that since acute crystal arthropathy can be misdiagnosed as 'culture-negative septic arthritis', introducing the pathway would improve diagnostic accuracy.This pathway provides a structured approach for investigating acutely swollen joints, distinguishing septic arthritis from crystal arthritis. Key features include a secure messaging app for multidisciplinary discussion and rheumatology-led point-of-care polarised light microscopy (POC PLM) <24 hours 6 days per week. A service evaluation of hospital inpatient data identified patients labelled with septic arthritis admitted between two periods: before (1 January 2019-30 November 2020) and after (27 September 2022-29 February 2024) pathway implementation. Emergency department (ED) patients discussed via the app were also analysed (27 September 2022-25 September 2023).Among ED patients, 92% received rheumatology input, and 100% underwent joint aspiration with rheumatologist-led crystal analysis in <24 hours. 68% avoided hospital admission, receiving same-day discharge. Of these, 53% were diagnosed with crystal arthropathy and were discharged with planned outpatient follow-up.Diagnostic accuracy increased for inpatients following pathway introduction. Joint aspirates increased from 50% to 76% (p=0.034). Culture-negative cases of septic arthritis reduced from 34% to 17% and culture positive cases increased from 41% to 76% (p<0.005). Crystal analysis increased from 19% to 28%. Positive blood cultures increased from 28% to 41%. Mean length of stay decreased from 26 to 23 days.A structured care pathway combining rheumatology-led POC PLM and multidisciplinary discussion increases diagnostic accuracy, facilitates admission avoidance and reduces hospital stay for patients with acute swollen joints. Rheumatology-led PLM is essential for the success of this pathway.

Keywords: Arthritis; Clinical Decision-Making; Continuous quality improvement; Emergency department; Evidence-Based Practice.

Figure 1. The ‘Hot Joint Pathway’. FBC, full blood count; CRP, C reactive protein; PT, prothrombin time; SIRS, systemic inflammatory response syndrome; INR, international normalised ratio; ED, emergency department; WCC, white cell count; EM, emergency medicine.

Figure 2. Joint aspirations, culture positive and culture-negative inpatient cases pre versus post introduction of the ‘Hot Joint Pathway’. Joint aspirations increased from 50% (16/32) prepathway to 76% (22/29) postpathway (p=0.034, 1-sided). Culture positive cases increased from 41% (95% CI 23.6% to 57.6%) to 76% (95% CI 60.4% to 91.6%) (p=0.009, 2-sided). Culture-negative cases decreased from 34% to 17% (p=0.155, 2-sided).

Figure 3. Outcome of cases reviewed via the ‘Hot Joint Pathway’ in the emergency department. CPPD, calcium pyrophosphate deposition; OA, osteoarthritis.

Figure 4. Example of multidisciplinary case discussion between ED and rheumatology via Siilo in the ‘Hot Joint Pathway’. This screenshot demonstrates real-time communication, including POC PLM results and management advice to facilitate rapid diagnosis and decision-making. ED, emergency department; POC PLM, point-of-care polarised light microscopy. ETOH, alcohol; ROM, range of motion.