Quantitative sacroiliac scintigraphy for pediatric patients: comparison of two methods

Quantitative bone scintigraphy is a useful method to diagnose sacroiliitis. However, there is significant overlap between healthy and pathological sacroiliac index (SI) values for adult patients, while there are no such sufficient data for children. This study was aimed mainly to assess normal SI values in different age groups of pediatric patients using 2 different quantitative methods.

Normally reported bone scans of 79 children were retrospectively reviewed. Two different methods were used for quantitation. For the first method, sacrum was used as a background site while L5 vertebra was used instead for the second method. Right/left SI values of both methods were compared with each other in relation with gender and different age groups, as group 1 (1-5 years), group 2 (6-10 years), group 3 (11-15 years) and group 4 (16-18 years). Additional comparison was made with a group of young-adult population of 21-30 years old as group 5 to assess the effect of age.

Gender-based comparison yielded significantly higher SI for females for the first method, while no significant difference existed for the second one. Significant increase in SI with both methods was found as age increased. Significantly lower SI was found from the second method, when similar age groups like group 1-2 or group 2-3 were compared with each other, while no such difference existed for the first method. For each individual patient from any age group, method-based comparison resulted in a significantly different SI with both methods.

In pediatric population, SI tends to increase as age increases. Quantitation method using sacrum as background yields significantly higher SI for female gender. Alternative use of L5 as background site for quantitation performs well in children. Since two methods resulted in significantly different SI, individualized cut-off values for each age group for any method are practically warranted.