The yield of bone scintigraphy in cancer and non-cancer patients: its association with indication and clarity of the referral question.

The yield of bone scintigraphy was assessed in a general hospital. A random 1:2 sample of the bone studies performed within a year was evaluated. The referral forms were judged to show absent, ambiguous or clear diagnostic questions. The indications for which the study was ordered were matched with the scintigraphic diagnosis, and yield was defined as the proportion of studies with relevant findings on scintigraphy. The overall yield was 23.5%. In cancer patients the yield was 27.2% and in repeat studies 40.2%. In non-cancer patients the yield was 19.8% and when scintigraphy was performed for the evaluation of specific disease entities it was 35.7%. Relatively low-yield indications in non-cancer patients were suspected metastases 11.1%, and evaluation of X-ray abnormalities 11.5%. An association between the clarity of the diagnostic question and the scintigraphic yield was detected in non-cancer patients. When a diagnostic question was absent the yield was 12%, ambiguous 19%, and when it was clear 26%. This correlation is probably attributed to better understanding of this common procedure, and better definition of the diagnostic question in patients with diverse clinical conditions as compared to cancer patients in whom the question always relates to the presence of bone metastases.