Which components of a bone scan for low back pain are really necessary

1782 Objectives The current protocol for bone scans performed for back pain at our institution consists of planar whole body images followed by SPECT of the thoracic, lumbar and sacral spine with low dose CT performed only over areas of abnormality identified on SPECT or on prior imaging. Overall camera time is ~45 minutes with ~18 minutes (40%) dedicated to planar scanning and the remainder to SPECT and CT. The purpose of this study was to assess the diagnostic performance of each of the three elements of this examination (planar, SPECT, CT) relative to the gold standard of SPECT plus CT. Methods Imaging records were searched for SPECT/CT examinations performed in patients less than 21 years old for back pain prior to July 15, 2015. Cases related to prior back surgery or systemic disease (e.g. JIA, CRMO, etc.) were excluded. The 100 most recently performed examinations were separated into their components (planar, SPECT, CT), anonymized and randomized and were reviewed by two of four reviewers with Nuclear Medicine specialization. Reviewers were blinded to each other’s interpretations. Two months after review of the individual components, each co-registered SPECT/CT examinations was reviewed by two of four reviewers, also in random, blinded fashion. The diagnosis and affected spinal level given by the two reviewers on the SPECT/CT examination served as the gold standard against which the components of the examination were compared. For SPECT/CT examinations in which both reviewers did not agree on the diagnosis, a third reviewer served as arbiter. Results Both reviewers agreed on the presence or absence of an abnormality for 87% (87/100) of the planar images, 72% (72/100) of the SPECT images and 77% (77/100) of the CT images. For SPECT/CT the two primary reviewers agreed on the presence or absence of any abnormality in 80% (80/100) of cases. The primary reviewers agreed on both the presence of an abnormality and specific diagnosis in 66% (66/100) of cases. Considering SPECT/CT, with arbitration as needed, as the gold standard, SPECT alone was 90% accurate in cases where both reviewers agreed with 88% sensitivity and 95% specificity for the detection of an abnormality. Limited CT was 75% accurate in cases where both reviewers agreed with 70% sensitivity and 87% specificity for the detection of an abnormality. Planar imaging, however, was only 41% accurate in cases where both reviewers agreed with 18% sensitivity and 100% specificity for the detection of an abnormality. Abnormalities outside of the spine potentially requiring further evaluation were identified on planar imaging in 14/100 cases. Conclusions In pediatric and young adult patients with uncomplicated low back pain, whole body planar imaging is only 41% accurate in identifying the presence or absence of potential causes of low back pain. Given the relatively poor diagnostic performance of whole body planar imaging and the fact that planar imaging identifies only a relatively small number of abnormalities outside of the thoracic, lumbar and sacral spine, not performing whole body planar imaging in this group of patients may be reasonable, allowing potential camera time savings of 40%.