Background/Purpose: For many years, the importance of bone scintigraphy to measure inflammation in the joints of patients with RA has been emphasized. Moreover, increased blood pool activity of involved joints in bone scintigraphy corresponds to inflammatory synovitis which is characteristic feature in early RA. Therefore, bone scintigraphy especially with blood pool phase, might be useful in suggesting early joint involvement in RA. The aim of this study was to investigate the usefulness of bone scintigraphy in the diagnosis of rheumatoid arthritis (RA) with assisting the 2010 ACR/EULAR classification criteria.

Methods: A total of 156 patients who firstly visited the rheumatology department and had taken bone scintigraphy and blood pool image with screening laboratory and radiologic tests to confirm RA diagnosis were retrospectively enrolled. Gold standard RA patients were defined as the patients who started disease modifying anti-rheumatic drugs within 3 months of their first visit. After dividing patients into two groups according to the presence or absence of arthritis on their first presentation, we evaluated the diagnostic validity of bone scintigraphy as an independent diagnostic tool (BS only) and as an assistant tool for physicians’ application of 1987 and 2010 criteria (BS assisted diagnosis) to detect RA. In BS assisted diagnosis, the number, symmetricity, and distribution of involved joints were evaluated with BS results instead of physician’s assessment.    

Results: Seventy-five (48.1%) of the 156 patients had active arthritis on physical examination (Group I) and the others of 81 patients did not have arthritis at first visit (Group II). Among them, 56 (74.7%) in group I and 5 (6.2%) in group II were RA patients, respectively. For group I patients (n=75), who were eligible to 2010 criteria, the sensitivity of the bone scintigraphy alone was extremely low (42.9%) with elevated specificity (100%), though those of 2010 criteria assessed by only physician (82.1% and 94.7%, respectively). For this group, the sensitivity of BS assisted diagnosis (75.0%) was slightly lower than that of the diagnosis by physician. For group II patients (n=81) who are not eligible for 2010 criteria, only BS or BS assisted diagnosis identified 2 more RA patients among 5 gold standard RA patients who did not satisfy either 1987 or 2010 criteria (Table).

Conclusion: In usual practice, BS assisted diagnosis is not superior to physician’s assessment, especially after appearance of 2010 ACR/EULAR classification criteria. However, bone scintigraphy is still helpful to rule out non RA patients in patients with arthritis and to find out RA patients among patients without arthritis on physical examination.

Table. Comparison of the diagnostic validities of the bone scintigraphy (BS) and BS assisted diagnosis

	Subjects	Sensitivity, %		Specificity, %	PPV, %	NPV, %	AUC (95% CI)
Group I. Patients with Arthritis at presentation (who eligible for 2010 criteria, n=75)
	BS only		42.9	100	100	37.3	–
1987 criteria	Physician only		66.0	99.2	97.4	86.1	0.864(0.770-0.958)
	Physician with BS		58.9	100	100	45.2	0.911(0.844-0.977)
2010 criteria	Physician only		82.1	94.7	97.9	64.3	0.923(0.803-1.0)
	Physician with BS		75.0	94.7	97.7	56.2	0.943(0.883-1.0)
Group II. Patients without Arthritis at presentation (who are not eligible for 2010 criteria, n=81)
	BS only	40.0		98.7	66.7	96.2	–
1987 criteria	Physician only	0		100	–	93.8	0.636 (0.362-0.909)
	Physician with BS	20.0		100	100	95.0	0.696 (0.355-1.0)
2010 criteria	Physician only	0		100	–	93.8	0.861 (0-1.0)
	Physician with BS	40.0		100	100	96.2	0.862 (0 -1.0)

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-bone-scintigraphy-still-useful-to-diagnose-rheumatoid-arthritis-after-the-appearance-of-2010-acreular-classification-criteria/