In preschool children, back pain should be viewed seriously. History of significant trauma will need X-rays to rule out fractures or dislocations. Night pain if constantly present should be investigated. In children where further workup is needed, the following tests are often done. Blood tests including complete blood count checking the red and white cell count, the differential white cell count, and platelet count.
Sedimentation rate is an indicator of any systemic inflammatory process in the body.
C-reactive protein also increases with inflammation, but gets back down to normal sooner than the sedimentation rate. X-rays of the spine, including the pelvis rules out any fractures or dislocations, any infection or tumors. While it does not define the actual pathology, e.g., trauma or infection or tumor, it localizes the area of pathology. This is an expensive, but accurate test to define the lesion being studied. The part of the body being studied is placed in a big machine with a large electromagnet that produces these radio waves.