LONDON, United Kingdom—For want of reliable data, "the opinion of an experienced doctor" remains the best guide to diagnosis and management of septic arthritis, concludes a systematic review by Catherine J. Mathews, MD, et al, published in Annals of the Rheumatic Diseases.¹ Dr. Mathews, at Queen Elizabeth Hospital, in London, reviewed 3291 articles using criteria set by the Royal College of Physicians Clinical Effectiveness and Evaluation Unit. Eighty articles met the inclusion criteria and were the basis for the systematic analysis of diagnosis, investigation, and management of septic arthritis.

"What is clear is that septic arthritis almost invariably presents over a period of up to 2 weeks as one or more hot, painful, swollen and restricted joints, and in this circumstance sepsis should be assumed until proved otherwise. The absence of a fever or raised white cell count cannot reliably exclude the diagnosis, nor can a negative synovial fluid culture. There is no gold standard for the diagnosis of septic arthritis, save that the overall judgment of an experienced clinician has proved superior to any laboratory or radiological investigation," Dr. Mathews writes.

The researchers defined septic arthritis as "joint sepsis caused by pathogenic inoculation of the joint by direct or haematogenous routes, rather than an immunological response to pathogens such as that seen in reactive arthritis."¹ Their goals were to identify signs, symptoms, or risk factors to aid diagnosis and to identify the evidence underlying the most common treatment strategies.

Their systematic analysis found that

•  staphylococci or streptococci cause 91% of septic arthritis cases.
•  Gram-negative organisms are more common in older patients.
•  risk factors include rheumatoid arthritis (RA) or osteoarthritis, prosthetic joints, low socioeconoic status, intravenous drug abuse, alcoholism, diabetes, previous intra-articular steroid injections, and cutaneous ulcers.

"In up to 22% of cases, more than one joint is affected, and, therefore, an oligoarticular or polyarticular presentation does not exclude the diagnosis of sepsis," the authors write.

How important is synovial fluid white cell count?

Dr. Mathews notes that total and differential white cell counts (WCCs) have been recommended as a way to distinguish infected and noninfected joints, although the systematic review did not provide clear support for this approach. "We conclude that the synovial fluid WCC is not sufficiently reliable a measure to exclude or confirm a diagnosis of septic arthritis," she says.

Techniques for microbiological examination of the synovial fluid are similarly controversial. Inoculation of synovial fluid into blood culture bottles may improve the yield from synovial fluid. However, polymerase chain reaction (PCR) was no better than bacterial culture for diagnosis staphylococcal or streptococcal joint infection. "Blood cultures may identify the causative organism even where synovial fluid culture is unrewarding," Dr. Mathews comments.

The standard two-pronged treatment of septic arthritis requires prompt use of antibiotics and removal of purulent material from the joint. Antibiotic choice and treatment regimen are largely empirical and based on the likelihood of the organism involved and modified by the results of Gram stain and culture [Table].

Table: Empiric treatment of suspected septic arthritis