Evaluation of quantitative sacroiliac scintigraphy for the early detection of sacroiliitis

Quantitative sacroiliac scintigraphy (QSS) was evaluated for the detection of sacroiliac (SI) joint disease before the appearance of radiographic/changes. QSS with fractional quantitation was done in 13 age- and sex-matched controls and 28 patients with different grades of radiographic sacroiliitis. The SI index of each joint was considered separately. The mean SI index values in patients with grade I radiographic sacroiliitis (1.54) and HLA-B27 positive patients with low back pain (1.50) were significantly (P less than 0.01) higher than the mean SI index of controls (1.22); but more than 50% of their SI index values were within the 97.5% confidence limits of the control range. The mean SI index values of patients with grade II (1.38) and grade III (1.34) radiographic sacroiliitis did not differ significantly from the mean SI index of controls (P greater than 0.05). Thus a large overlap between the normal and abnormal ranges of sacroiliac ratios limits the utility of quantitative sacroiliac scintigraphy for the early diagnosis of sacroiliac joint disease.