As seen in figure 1, local diagnostic reference levels were comparable when either age or weight groupings were used for our patient population up to the age of 14 (50kg) for both Chest and Abdomen studies. Weight groupings demonstrated slightly higher specificity (lower standard deviation) only for abdomen exams. However, there was a difference in results for the older age group in both types of study.

The audit of patient age for our study, shown in figure 2, verified that the median and mean ages of our patients in each age group were close to the mid-point of the European guidelines age ranges. This demonstrates that our patient sample was a good representation of the corresponding age groups.

The audit of patient weight vs age, shown in figure 3, indicated that the weight of our population in the 0-10Y age groups is consistent with weight ranges in European guidelines. However, the mean and median weight for the oldest age group was at the lower end of the European guidelines weight range.  

Figure 4 show the distribution of our population’s weight for the 5, 10 and 15Y age groups. These populations demonstrate two peaks in patient weight. This distribution may be due to different ethnic populations or clinical indications for imaging referral. Although for the 5 and 10Y groups the two peaks are balanced, for the 15Y group the 50kg peak is more pronounced. This can help explain why local diagnostic reference levels are lower when age is used as a determinant rather than weight, as seen in figure 1 for the older age groups.

In conclusion, for our paediatric patient population, local diagnostic reference levels are comparable for both chest and abdominal general x-ray imaging whether weight-based or age-base groups are used for younger patient ages whilst a difference can be seen in the oldest age group.