Background: Bone scintigraphy used as a diagnostic technique frequently yields non-specific intense uptake by vertebrae. Bone biopsy may therefore be required to establish a diagnosis in cases of Paget's disease of bone. The aim of the study was to ascertain the sensitivity and specificity of two new images-heart sign and clover sign-in Paget's disease of bone.
Methods: Two expert rheumatologists analyzed 294 bone scintigraphies of patients with vertebral involvement: 204 without and 90 with Paget's disease. The presence or absence of the clover or heart signs was determined in each scintigraphy. A specificity and sensitivity study was performed with the data obtained. A study of concordance was made between two radiologists blinded to the real diagnosis. Each one analyzed 120 scintigraphies for the presence and absence of the signs: 40 with Paget's disease and clover and/or heart signs (selected from the initial 90 cases), 40 with Paget's disease with neither sign and 40 selected from the pool of 4000 scintigraphies of patients with vertebral involvement, with images easily mistaken for these signs (vertebral collapse, osteoarthritis and bone metastases). Kappa statistics were calculated.
Findings: Sensitivity of both signs for Paget's disease of bone was low: 44% (95% CI 34.0 to 55.3). However, specificity was excellent: 100% (95% CI 98.2 to 100). Inter-radiologist concordance was almost perfect: Kappa 0.86 (95% CI 0.77 to 0.95).
Interpretation: The heart and clover signs are highly specific (probably pathognomonic) of Paget's disease of bone. In cases with doubtful radiologic images, these findings on scintigraphic vertebral images may afford a definitive diagnosis of Paget's disease of bone and thus obviate further confirmatory invasive diagnostic procedures.