The contribution of bone SPECT to the diagnosis of bone metastases in an African population.

Background: A number of studies have demonstrated the value of performing spinal SPECT in addition to planar scintigraphy for the diagnosis of bone metastases. This has not been demonstrated in an African population, however, where patients typically present with more advanced disease.

Aim: To investigate the contribution of bone SPECT to the diagnosis of bone metastases in an African population.

Methods: In a retrospective survey the studies of all patients with known primary tumours who underwent skeletal scintigraphy for the diagnosis of bone metastases during one calendar year were reviewed. The studies of patients who underwent both planar imaging and SPECT were reinterpreted. Blinded to the SPECT study, the planar studies were graded for probability of metastatic disease using a four-point scale, and the number of spinal lesions was noted. This was repeated with the planar and SPECT studies reviewed together. The interpretation using the planar images alone was compared with that obtained after the addition of SPECT using non-parametric tests. Of a total of 576 patients, 119 (45 men and 74 women) underwent planar and SPECT imaging.

Results: The addition of SPECT resulted in a significant change in the interpretation of these studies (P<0.05), and a significantly lower proportion of patients had equivocal gradings (P<0.01). However, the actual numbers of patients affected was relatively small, varying from six to 21, representing about 5-18% of the 119 patients who underwent an additional SPECT. Furthermore, of the total population of 576 patients with known malignancies undergoing bone scintigraphy for bone metastases, the availability of SPECT only resulted in an altered classification in 1-4%. Equivocal planar gradings were far more likely to be altered following the addition of SPECT. The addition of SPECT also resulted in the detection of significantly more spinal lesions (P<0.01).

Conclusion: In a setting where SPECT is not easily available, planar imaging alone is still adequate in the vast majority of cases.