Utility of common investigations for suspected inflammatory arthritis in adults.

Inflammatory arthritis may be the principal feature or one component of an inflammatory rheumatological disease. It is a clinical diagnosis, principally made based on the patient's history and examination. Specific investigations, such as rheumatoid factor and human leucocyte antigen B27 gene, may support the diagnosis in the context of a suggestive clinical presentation, but a diagnosis cannot be made based on these tests alone because positive results may also be seen in healthy individuals. To reduce the likelihood of false positive results, laboratory and radiological investigations should be tailored to the suspected diagnosis based on pretest probability. While musculoskeletal symptoms are a common presentation in general practice, specific features that increase suspicion of an inflammatory arthritis include prolonged morning stiffness (more than 1 hour) that is improved by exercise or movement. A broad 'rheumatological panel' increases the likelihood of false positive results and should be avoided to prevent unnecessary further investigations and treatment, and unwarranted anxiety in both the patient and the doctor.