Musculoskeletal ultrasound was associated with more than double gains in diagnostic certainty in a prospective cohort of consecutive patients referred for the evaluation of inflammatory arthritis.
Consistent with previous studies, “We found that musculoskeletal ultrasound greatly increased the diagnostic certainty for inflammatory arthritis in general and for RA [rheumatoid arthritis] in particular,” wrote Dr. Hamed Rezaei and coauthors at the Karolinska Institute in Stockholm.
When the investigators added musculoskeletal ultrasound (MSUS) to the assessment of 103 previously undiagnosed persons (mean age, 50 years; 74% female) who were referred to a single center for suspected inflammatory arthritis, the percentage of patients with a confirmed diagnosis rose from 33% before MSUS to 71.8% after (P < .001). Diagnostic confirmation specifically for RA went from 31.1% before MSUS to 61.2% after (P < .001). The imaging results were consistent with the final diagnosis in 95% of patients (Arthritis Res. Ther. 2014;16:448 [doi:10.1186/s13075-014-0448-6]).
The initial clinical assessments included joint examination, tests for acute-phase reactants, rheumatoid factor and anticitrullinated peptide antibody, and radiographs of hands and feet when indicated. A rheumatologist determined the probable presence of inflammatory arthritis generally, and rheumatoid arthritis specifically using a 5-point scale that assessed probability of the diagnosis with 1 point for less than a 20% probability, 2 points for greater than or equal to 20% but less than a 40% probability, and so on.
Following the initial assessment, the wrist, metacarpophalangeal, proximal interphalangeal joints 2-5 in both hands, metatarsophalangeal joints 2-5 in both feet, and any symptomatic joints, were imaged. The rheumatologist was then given the images and asked to use the same scale to once again assess the diagnostic probabilities.
Although the authors of the study pointed to the strength of their probabilistic approach to determining if musculoskeletal imaging improved diagnostic certainty on a 5-point scale, they acknowledged that the treating rheumatologist who performed the initial assessment was aware of her/his own scoring before the musculoskeletal imaging was done and may have felt either motivated to improve the result, or simply operated under the assumption that more information that may lead to increase posttest probability would be available later. However, when the cases were randomly rescored by another rheumatologist, results were reported to be almost identical.
“As expected, the likelihood of having any inflammatory arthritis and especially of having RA in patients with early arthritis symptoms increased with the presence of MSUS findings,” Dr. Rezaei and his colleagues wrote. “MSUS also improved diagnostic accuracy compared to clinical assessment alone, when analyzed in a classical (deterministic) manner; as also shown previously in more than 95% of patients there was agreement between MSUS finding and final diagnosis.”
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