Tenosynovial fluid white cell count complements ultrasound to rule out inflammatory tenosynovitis
Although a negative Doppler ultrasound can help rule out inflammatory disease in tenosynovitis, positive results are nonspecific and warrant tenosynovial fluid testing, according to data published in the Annals of the Rheumatic Diseases.
The researchers additionally concluded that, compared with synovial fluid, a lower tenosynovial fluid white cell count better discriminates between inflammatory conditions from noninflammatory conditions.
“While the leukocyte range for synovial fluid and bursal fluid in rheumatic conditions has been previously described, this is the first study to define the range of tenosynovial leukocyte counts in rheumatic conditions,” Eugene Kissin, MD, of Boston University Medical Center, told Healio Rheumatology. “This is also the first time tenosynovial fluid leukocyte counts have been correlated with Doppler ultrasound signal in the affected tendon sheath.”
To analyze the characteristics and diagnostic utility of Doppler ultrasound and tenosynovial fluid in tenosynovitis among patients with various common rheumatic conditions, Kissin and colleagues conducted a cross-sectional study of 112 participants from 14 private and academic practices in the United States. Between November 2017 and May 2019, participants with tenosynovitis underwent Doppler ultrasound, as well as ultrasound-guided tenosynovial fluid aspiration for white cell count and crystal analysis. Tenosynovial Doppler scores were then graded semi-quantitatively.
The researchers compared tenosynovial fluid white cell count and Doppler scores using Kruskal-Wallis tests and logistic regression between noninflammatory, inflammatory and crystal-related conditions. They also used receiver operating curves, sensitivity and specificity to assess the ability of white cell counts and Doppler scores to differentiate between inflammatory and noninflammatory diseases.
One hundred participants were included in the final analysis after 12 aspirations failed to produce tenosynovial fluid. The two most common post-aspiration clinical diagnoses were rheumatoid arthritis with 20 cases and calcium pyrophosphate deposition with 18 cases. Spondyloarthropathy and mechanical cause were responsible for 12 cases each, followed by gout with eight cases. Forty-eight participants had inflammatory conditions, 26 had crystal-related diseases and 16 were non-inflammatory.
According to the researchers, Doppler signal was present in 93.7% of patients with inflammatory disease, and was more frequent among those with an inflammatory condition, compared with non-inflammatory conditions (OR = 6.82; 95%CI, 1.41-32.97). The median tenosynovial fluid white cell count per 109 per liter was significantly higher in those with inflammatory disease, at 2.58 (P < .001), and crystal-related conditions, at 1.07 (P < .01), compared with the non-inflammatory group, which had a median of 0.38.
A white cell count cut-off of at least 0.67 per 109 per liter optimally differentiated inflammatory from non-inflammatory diseases, with a sensitivity and specificity of 81.3% each. Among patients with inflammatory disease, 41.7% demonstrated a white cell count of less than 2 per 109 liters.
“A negative Doppler ultrasound, when performed with well-tuned, sensitive ultrasound equipment, and operated by rheumatologists certified in musculoskeletal ultrasound, can help exclude inflammatory causes of tenosynovitis,” Kissin said. “However, if there is positive Doppler signal, then a tenosynovial aspirate would be needed to confirm an inflammatory cause of the effusion.”
He added: “Since our study was performed at 14 clinical sites, including both academic and private practice settings, with an array of ultrasound equipment typically used by rheumatologists in the United States, we believe that our findings are generalizable, and applicable to the typical rheumatology practice.” – by Jason Laday
Disclosures: The researchers report no relevant financial disclosures.